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Review articles: purpose, process, and structure

• Published: 02 October 2017
• Volume 46 , pages 1–5, ( 2018 )

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• Robert W. Palmatier 1 ,
• Mark B. Houston 2 &
• John Hulland 3  

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Many research disciplines feature high-impact journals that are dedicated outlets for review papers (or review–conceptual combinations) (e.g., Academy of Management Review , Psychology Bulletin , Medicinal Research Reviews ). The rationale for such outlets is the premise that research integration and synthesis provides an important, and possibly even a required, step in the scientific process. Review papers tend to include both quantitative (i.e., meta-analytic, systematic reviews) and narrative or more qualitative components; together, they provide platforms for new conceptual frameworks, reveal inconsistencies in the extant body of research, synthesize diverse results, and generally give other scholars a “state-of-the-art” snapshot of a domain, often written by topic experts (Bem 1995 ). Many premier marketing journals publish meta-analytic review papers too, though authors often must overcome reviewers’ concerns that their contributions are limited due to the absence of “new data.” Furthermore, relatively few non-meta-analysis review papers appear in marketing journals, probably due to researchers’ perceptions that such papers have limited publication opportunities or their beliefs that the field lacks a research tradition or “respect” for such papers. In many cases, an editor must provide strong support to help such review papers navigate the review process. Yet, once published, such papers tend to be widely cited, suggesting that members of the field find them useful (see Bettencourt and Houston 2001 ).

In this editorial, we seek to address three topics relevant to review papers. First, we outline a case for their importance to the scientific process, by describing the purpose of review papers . Second, we detail the review paper editorial initiative conducted over the past two years by the Journal of the Academy of Marketing Science ( JAMS ), focused on increasing the prevalence of review papers. Third, we describe a process and structure for systematic ( i.e. , non-meta-analytic) review papers , referring to Grewal et al. ( 2018 ) insights into parallel meta-analytic (effects estimation) review papers. (For some strong recent examples of marketing-related meta-analyses, see Knoll and Matthes 2017 ; Verma et al. 2016 ).

Purpose of review papers

In their most general form, review papers “are critical evaluations of material that has already been published,” some that include quantitative effects estimation (i.e., meta-analyses) and some that do not (i.e., systematic reviews) (Bem 1995 , p. 172). They carefully identify and synthesize relevant literature to evaluate a specific research question, substantive domain, theoretical approach, or methodology and thereby provide readers with a state-of-the-art understanding of the research topic. Many of these benefits are highlighted in Hanssens’ ( 2018 ) paper titled “The Value of Empirical Generalizations in Marketing,” published in this same issue of JAMS.

The purpose of and contributions associated with review papers can vary depending on their specific type and research question, but in general, they aim to

Resolve definitional ambiguities and outline the scope of the topic.

Provide an integrated, synthesized overview of the current state of knowledge.

Identify inconsistencies in prior results and potential explanations (e.g., moderators, mediators, measures, approaches).

Evaluate existing methodological approaches and unique insights.

Develop conceptual frameworks to reconcile and extend past research.

Describe research insights, existing gaps, and future research directions.

Not every review paper can offer all of these benefits, but this list represents their key contributions. To provide a sufficient contribution, a review paper needs to achieve three key standards. First, the research domain needs to be well suited for a review paper, such that a sufficient body of past research exists to make the integration and synthesis valuable—especially if extant research reveals theoretical inconsistences or heterogeneity in its effects. Second, the review paper must be well executed, with an appropriate literature collection and analysis techniques, sufficient breadth and depth of literature coverage, and a compelling writing style. Third, the manuscript must offer significant new insights based on its systematic comparison of multiple studies, rather than simply a “book report” that describes past research. This third, most critical standard is often the most difficult, especially for authors who have not “lived” with the research domain for many years, because achieving it requires drawing some non-obvious connections and insights from multiple studies and their many different aspects (e.g., context, method, measures). Typically, after the “review” portion of the paper has been completed, the authors must spend many more months identifying the connections to uncover incremental insights, each of which takes time to detail and explicate.

The increasing methodological rigor and technical sophistication of many marketing studies also means that they often focus on smaller problems with fewer constructs. By synthesizing these piecemeal findings, reconciling conflicting evidence, and drawing a “big picture,” meta-analyses and systematic review papers become indispensable to our comprehensive understanding of a phenomenon, among both academic and practitioner communities. Thus, good review papers provide a solid platform for future research, in the reviewed domain but also in other areas, in that researchers can use a good review paper to learn about and extend key insights to new areas.

This domain extension, outside of the core area being reviewed, is one of the key benefits of review papers that often gets overlooked. Yet it also is becoming ever more important with the expanding breadth of marketing (e.g., econometric modeling, finance, strategic management, applied psychology, sociology) and the increasing velocity in the accumulation of marketing knowledge (e.g., digital marketing, social media, big data). Against this backdrop, systematic review papers and meta-analyses help academics and interested managers keep track of research findings that fall outside their main area of specialization.

JAMS’ review paper editorial initiative

With a strong belief in the importance of review papers, the editorial team of JAMS has purposely sought out leading scholars to provide substantive review papers, both meta-analysis and systematic, for publication in JAMS . Many of the scholars approached have voiced concerns about the risk of such endeavors, due to the lack of alternative outlets for these types of papers. Therefore, we have instituted a unique process, in which the authors develop a detailed outline of their paper, key tables and figures, and a description of their literature review process. On the basis of this outline, we grant assurances that the contribution hurdle will not be an issue for publication in JAMS , as long as the authors execute the proposed outline as written. Each paper still goes through the normal review process and must meet all publication quality standards, of course. In many cases, an Area Editor takes an active role to help ensure that each paper provides sufficient insights, as required for a high-quality review paper. This process gives the author team confidence to invest effort in the process. An analysis of the marketing journals in the Financial Times (FT 50) journal list for the past five years (2012–2016) shows that JAMS has become the most common outlet for these papers, publishing 31% of all review papers that appeared in the top six marketing journals.

As a next step in positioning JAMS as a receptive marketing outlet for review papers, we are conducting a Thought Leaders Conference on Generalizations in Marketing: Systematic Reviews and Meta-Analyses , with a corresponding special issue (see www.springer.com/jams ). We will continue our process of seeking out review papers as an editorial strategy in areas that could be advanced by the integration and synthesis of extant research. We expect that, ultimately, such efforts will become unnecessary, as authors initiate review papers on topics of their own choosing to submit them to JAMS . In the past two years, JAMS already has increased the number of papers it publishes annually, from just over 40 to around 60 papers per year; this growth has provided “space” for 8–10 review papers per year, reflecting our editorial target.

Consistent with JAMS ’ overall focus on managerially relevant and strategy-focused topics, all review papers should reflect this emphasis. For example, the domains, theories, and methods reviewed need to have some application to past or emerging managerial research. A good rule of thumb is that the substantive domain, theory, or method should attract the attention of readers of JAMS .

The efforts of multiple editors and Area Editors in turn have generated a body of review papers that can serve as useful examples of the different types and approaches that JAMS has published.

Domain-based review papers

Domain-based review papers review, synthetize, and extend a body of literature in the same substantive domain. For example, in “The Role of Privacy in Marketing” (Martin and Murphy 2017 ), the authors identify and define various privacy-related constructs that have appeared in recent literature. Then they examine the different theoretical perspectives brought to bear on privacy topics related to consumers and organizations, including ethical and legal perspectives. These foundations lead in to their systematic review of privacy-related articles over a clearly defined date range, from which they extract key insights from each study. This exercise of synthesizing diverse perspectives allows these authors to describe state-of-the-art knowledge regarding privacy in marketing and identify useful paths for research. Similarly, a new paper by Cleeren et al. ( 2017 ), “Marketing Research on Product-Harm Crises: A Review, Managerial Implications, and an Agenda for Future Research,” provides a rich systematic review, synthesizes extant research, and points the way forward for scholars who are interested in issues related to defective or dangerous market offerings.

Theory-based review papers

Theory-based review papers review, synthetize, and extend a body of literature that uses the same underlying theory. For example, Rindfleisch and Heide’s ( 1997 ) classic review of research in marketing using transaction cost economics has been cited more than 2200 times, with a significant impact on applications of the theory to the discipline in the past 20 years. A recent paper in JAMS with similar intent, which could serve as a helpful model, focuses on “Resource-Based Theory in Marketing” (Kozlenkova et al. 2014 ). The article dives deeply into a description of the theory and its underlying assumptions, then organizes a systematic review of relevant literature according to various perspectives through which the theory has been applied in marketing. The authors conclude by identifying topical domains in marketing that might benefit from additional applications of the theory (e.g., marketing exchange), as well as related theories that could be integrated meaningfully with insights from the resource-based theory.

Method-based review papers

Method-based review papers review, synthetize, and extend a body of literature that uses the same underlying method. For example, in “Event Study Methodology in the Marketing Literature: An Overview” (Sorescu et al. 2017 ), the authors identify published studies in marketing that use an event study methodology. After a brief review of the theoretical foundations of event studies, they describe in detail the key design considerations associated with this method. The article then provides a roadmap for conducting event studies and compares this approach with a stock market returns analysis. The authors finish with a summary of the strengths and weaknesses of the event study method, which in turn suggests three main areas for further research. Similarly, “Discriminant Validity Testing in Marketing: An Analysis, Causes for Concern, and Proposed Remedies” (Voorhies et al. 2016 ) systematically reviews existing approaches for assessing discriminant validity in marketing contexts, then uses Monte Carlo simulation to determine which tests are most effective.

Our long-term editorial strategy is to make sure JAMS becomes and remains a well-recognized outlet for both meta-analysis and systematic managerial review papers in marketing. Ideally, review papers would come to represent 10%–20% of the papers published by the journal.

Process and structure for review papers

In this section, we review the process and typical structure of a systematic review paper, which lacks any long or established tradition in marketing research. The article by Grewal et al. ( 2018 ) provides a summary of effects-focused review papers (i.e., meta-analyses), so we do not discuss them in detail here.

Systematic literature review process

Some review papers submitted to journals take a “narrative” approach. They discuss current knowledge about a research domain, yet they often are flawed, in that they lack criteria for article inclusion (or, more accurately, article exclusion), fail to discuss the methodology used to evaluate included articles, and avoid critical assessment of the field (Barczak 2017 ). Such reviews tend to be purely descriptive, with little lasting impact.

In contrast, a systematic literature review aims to “comprehensively locate and synthesize research that bears on a particular question, using organized, transparent, and replicable procedures at each step in the process” (Littell et al. 2008 , p. 1). Littell et al. describe six key steps in the systematic review process. The extent to which each step is emphasized varies by paper, but all are important components of the review.

Topic formulation . The author sets out clear objectives for the review and articulates the specific research questions or hypotheses that will be investigated.

Study design . The author specifies relevant problems, populations, constructs, and settings of interest. The aim is to define explicit criteria that can be used to assess whether any particular study should be included in or excluded from the review. Furthermore, it is important to develop a protocol in advance that describes the procedures and methods to be used to evaluate published work.

Sampling . The aim in this third step is to identify all potentially relevant studies, including both published and unpublished research. To this end, the author must first define the sampling unit to be used in the review (e.g., individual, strategic business unit) and then develop an appropriate sampling plan.

Data collection . By retrieving the potentially relevant studies identified in the third step, the author can determine whether each study meets the eligibility requirements set out in the second step. For studies deemed acceptable, the data are extracted from each study and entered into standardized templates. These templates should be based on the protocols established in step 2.

Data analysis . The degree and nature of the analyses used to describe and examine the collected data vary widely by review. Purely descriptive analysis is useful as a starting point but rarely is sufficient on its own. The examination of trends, clusters of ideas, and multivariate relationships among constructs helps flesh out a deeper understanding of the domain. For example, both Hult ( 2015 ) and Huber et al. ( 2014 ) use bibliometric approaches (e.g., examine citation data using multidimensional scaling and cluster analysis techniques) to identify emerging versus declining themes in the broad field of marketing.

Reporting . Three key aspects of this final step are common across systematic reviews. First, the results from the fifth step need to be presented, clearly and compellingly, using narratives, tables, and figures. Second, core results that emerge from the review must be interpreted and discussed by the author. These revelatory insights should reflect a deeper understanding of the topic being investigated, not simply a regurgitation of well-established knowledge. Third, the author needs to describe the implications of these unique insights for both future research and managerial practice.

A new paper by Watson et al. ( 2017 ), “Harnessing Difference: A Capability-Based Framework for Stakeholder Engagement in Environmental Innovation,” provides a good example of a systematic review, starting with a cohesive conceptual framework that helps establish the boundaries of the review while also identifying core constructs and their relationships. The article then explicitly describes the procedures used to search for potentially relevant papers and clearly sets out criteria for study inclusion or exclusion. Next, a detailed discussion of core elements in the framework weaves published research findings into the exposition. The paper ends with a presentation of key implications and suggestions for the next steps. Similarly, “Marketing Survey Research Best Practices: Evidence and Recommendations from a Review of JAMS Articles” (Hulland et al. 2017 ) systematically reviews published marketing studies that use survey techniques, describes recent trends, and suggests best practices. In their review, Hulland et al. examine the entire population of survey papers published in JAMS over a ten-year span, relying on an extensive standardized data template to facilitate their subsequent data analysis.

Structure of systematic review papers

There is no cookie-cutter recipe for the exact structure of a useful systematic review paper; the final structure depends on the authors’ insights and intended points of emphasis. However, several key components are likely integral to a paper’s ability to contribute.

Depth and rigor

Systematic review papers must avoid falling in to two potential “ditches.” The first ditch threatens when the paper fails to demonstrate that a systematic approach was used for selecting articles for inclusion and capturing their insights. If a reader gets the impression that the author has cherry-picked only articles that fit some preset notion or failed to be thorough enough, without including articles that make significant contributions to the field, the paper will be consigned to the proverbial side of the road when it comes to the discipline’s attention.

Authors that fall into the other ditch present a thorough, complete overview that offers only a mind-numbing recitation, without evident organization, synthesis, or critical evaluation. Although comprehensive, such a paper is more of an index than a useful review. The reviewed articles must be grouped in a meaningful way to guide the reader toward a better understanding of the focal phenomenon and provide a foundation for insights about future research directions. Some scholars organize research by scholarly perspectives (e.g., the psychology of privacy, the economics of privacy; Martin and Murphy 2017 ); others classify the chosen articles by objective research aspects (e.g., empirical setting, research design, conceptual frameworks; Cleeren et al. 2017 ). The method of organization chosen must allow the author to capture the complexity of the underlying phenomenon (e.g., including temporal or evolutionary aspects, if relevant).

Replicability

Processes for the identification and inclusion of research articles should be described in sufficient detail, such that an interested reader could replicate the procedure. The procedures used to analyze chosen articles and extract their empirical findings and/or key takeaways should be described with similar specificity and detail.

We already have noted the potential usefulness of well-done review papers. Some scholars always are new to the field or domain in question, so review papers also need to help them gain foundational knowledge. Key constructs, definitions, assumptions, and theories should be laid out clearly (for which purpose summary tables are extremely helpful). An integrated conceptual model can be useful to organize cited works. Most scholars integrate the knowledge they gain from reading the review paper into their plans for future research, so it is also critical that review papers clearly lay out implications (and specific directions) for research. Ideally, readers will come away from a review article filled with enthusiasm about ways they might contribute to the ongoing development of the field.

Helpful format

Because such a large body of research is being synthesized in most review papers, simply reading through the list of included studies can be exhausting for readers. We cannot overstate the importance of tables and figures in review papers, used in conjunction with meaningful headings and subheadings. Vast literature review tables often are essential, but they must be organized in a way that makes their insights digestible to the reader; in some cases, a sequence of more focused tables may be better than a single, comprehensive table.

In summary, articles that review extant research in a domain (topic, theory, or method) can be incredibly useful to the scientific progress of our field. Whether integrating the insights from extant research through a meta-analysis or synthesizing them through a systematic assessment, the promised benefits are similar. Both formats provide readers with a useful overview of knowledge about the focal phenomenon, as well as insights on key dilemmas and conflicting findings that suggest future research directions. Thus, the editorial team at JAMS encourages scholars to continue to invest the time and effort to construct thoughtful review papers.

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Foster School of Business, University of Washington, Box: 353226, Seattle, WA, 98195-3226, USA

Robert W. Palmatier

Neeley School of Business, Texas Christian University, Fort Worth, TX, USA

Mark B. Houston

Terry College of Business, University of Georgia, Athens, GA, USA

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Palmatier, R.W., Houston, M.B. & Hulland, J. Review articles: purpose, process, and structure. J. of the Acad. Mark. Sci. 46 , 1–5 (2018). https://doi.org/10.1007/s11747-017-0563-4

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Published : 02 October 2017

Issue Date : January 2018

DOI : https://doi.org/10.1007/s11747-017-0563-4

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How to Write a Peer Review

When you write a peer review for a manuscript, what should you include in your comments? What should you leave out? And how should the review be formatted?

This guide provides quick tips for writing and organizing your reviewer report.

Review Outline

Use an outline for your reviewer report so it’s easy for the editors and author to follow. This will also help you keep your comments organized.

Think about structuring your review like an inverted pyramid. Put the most important information at the top, followed by details and examples in the center, and any additional points at the very bottom.

Here’s how your outline might look:

1. Summary of the research and your overall impression

In your own words, summarize what the manuscript claims to report. This shows the editor how you interpreted the manuscript and will highlight any major differences in perspective between you and the other reviewers. Give an overview of the manuscript’s strengths and weaknesses. Think about this as your “take-home” message for the editors. End this section with your recommended course of action.

2. Discussion of specific areas for improvement

It’s helpful to divide this section into two parts: one for major issues and one for minor issues. Within each section, you can talk about the biggest issues first or go systematically figure-by-figure or claim-by-claim. Number each item so that your points are easy to follow (this will also make it easier for the authors to respond to each point). Refer to specific lines, pages, sections, or figure and table numbers so the authors (and editors) know exactly what you’re talking about.

Major vs. minor issues

What’s the difference between a major and minor issue? Major issues should consist of the essential points the authors need to address before the manuscript can proceed. Make sure you focus on what is  fundamental for the current study . In other words, it’s not helpful to recommend additional work that would be considered the “next step” in the study. Minor issues are still important but typically will not affect the overall conclusions of the manuscript. Here are some examples of what would might go in the “minor” category:

• Missing references (but depending on what is missing, this could also be a major issue)
• Technical clarifications (e.g., the authors should clarify how a reagent works)
• Data presentation (e.g., the authors should present p-values differently)
• Typos, spelling, grammar, and phrasing issues

3. Any other points

Confidential comments for the editors.

Some journals have a space for reviewers to enter confidential comments about the manuscript. Use this space to mention concerns about the submission that you’d want the editors to consider before sharing your feedback with the authors, such as concerns about ethical guidelines or language quality. Any serious issues should be raised directly and immediately with the journal as well.

This section is also where you will disclose any potentially competing interests, and mention whether you’re willing to look at a revised version of the manuscript.

Do not use this space to critique the manuscript, since comments entered here will not be passed along to the authors.  If you’re not sure what should go in the confidential comments, read the reviewer instructions or check with the journal first before submitting your review. If you are reviewing for a journal that does not offer a space for confidential comments, consider writing to the editorial office directly with your concerns.

Get this outline in a template

Giving Feedback

Giving feedback is hard. Giving effective feedback can be even more challenging. Remember that your ultimate goal is to discuss what the authors would need to do in order to qualify for publication. The point is not to nitpick every piece of the manuscript. Your focus should be on providing constructive and critical feedback that the authors can use to improve their study.

If you’ve ever had your own work reviewed, you already know that it’s not always easy to receive feedback. Follow the golden rule: Write the type of review you’d want to receive if you were the author. Even if you decide not to identify yourself in the review, you should write comments that you would be comfortable signing your name to.

In your comments, use phrases like “ the authors’ discussion of X” instead of “ your discussion of X .” This will depersonalize the feedback and keep the focus on the manuscript instead of the authors.

General guidelines for effective feedback

• Justify your recommendation with concrete evidence and specific examples.
• Be specific so the authors know what they need to do to improve.
• Be thorough. This might be the only time you read the manuscript.
• Be professional and respectful. The authors will be reading these comments too.
• Remember to say what you liked about the manuscript!

Don’t

• Recommend additional experiments or  unnecessary elements that are out of scope for the study or for the journal criteria.
• Tell the authors exactly how to revise their manuscript—you don’t need to do their work for them.
• Use the review to promote your own research or hypotheses.
• Focus on typos and grammar. If the manuscript needs significant editing for language and writing quality, just mention this in your comments.
• Submit your review without proofreading it and checking everything one more time.

Before and After: Sample Reviewer Comments

Keeping in mind the guidelines above, how do you put your thoughts into words? Here are some sample “before” and “after” reviewer comments

✗ Before

“The authors appear to have no idea what they are talking about. I don’t think they have read any of the literature on this topic.”

✓ After

“The study fails to address how the findings relate to previous research in this area. The authors should rewrite their Introduction and Discussion to reference the related literature, especially recently published work such as Darwin et al.”

“The writing is so bad, it is practically unreadable. I could barely bring myself to finish it.”

“While the study appears to be sound, the language is unclear, making it difficult to follow. I advise the authors work with a writing coach or copyeditor to improve the flow and readability of the text.”

“It’s obvious that this type of experiment should have been included. I have no idea why the authors didn’t use it. This is a big mistake.”

“The authors are off to a good start, however, this study requires additional experiments, particularly [type of experiment]. Alternatively, the authors should include more information that clarifies and justifies their choice of methods.”

Suggested Language for Tricky Situations

You might find yourself in a situation where you’re not sure how to explain the problem or provide feedback in a constructive and respectful way. Here is some suggested language for common issues you might experience.

What you think : The manuscript is fatally flawed. What you could say: “The study does not appear to be sound” or “the authors have missed something crucial”.

What you think : You don’t completely understand the manuscript. What you could say : “The authors should clarify the following sections to avoid confusion…”

What you think : The technical details don’t make sense. What you could say : “The technical details should be expanded and clarified to ensure that readers understand exactly what the researchers studied.”

What you think: The writing is terrible. What you could say : “The authors should revise the language to improve readability.”

What you think : The authors have over-interpreted the findings. What you could say : “The authors aim to demonstrate [XYZ], however, the data does not fully support this conclusion. Specifically…”

What does a good review look like?

Check out the peer review examples at F1000 Research to see how other reviewers write up their reports and give constructive feedback to authors.

Time to Submit the Review!

Be sure you turn in your report on time. Need an extension? Tell the journal so that they know what to expect. If you need a lot of extra time, the journal might need to contact other reviewers or notify the author about the delay.

Tip: Building a relationship with an editor

You’ll be more likely to be asked to review again if you provide high-quality feedback and if you turn in the review on time. Especially if it’s your first review for a journal, it’s important to show that you are reliable. Prove yourself once and you’ll get asked to review again!

• Getting started as a reviewer
• Responding to an invitation
• Reading a manuscript
• Writing a peer review

The contents of the Peer Review Center are also available as a live, interactive training session, complete with slides, talking points, and activities. …

The contents of the Writing Center are also available as a live, interactive training session, complete with slides, talking points, and activities. …

There’s a lot to consider when deciding where to submit your work. Learn how to choose a journal that will help your study reach its audience, while reflecting your values as a researcher…

• Research Process

Writing a good review article

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Table of Contents

As a young researcher, you might wonder how to start writing your first review article, and the extent of the information that it should contain. A review article is a comprehensive summary of the current understanding of a specific research topic and is based on previously published research. Unlike research papers, it does not contain new results, but can propose new inferences based on the combined findings of previous research.

Types of review articles

Review articles are typically of three types: literature reviews, systematic reviews, and meta-analyses.

A literature review is a general survey of the research topic and aims to provide a reliable and unbiased account of the current understanding of the topic.

A systematic review , in contrast, is more specific and attempts to address a highly focused research question. Its presentation is more detailed, with information on the search strategy used, the eligibility criteria for inclusion of studies, the methods utilized to review the collected information, and more.

A meta-analysis is similar to a systematic review in that both are systematically conducted with a properly defined research question. However, unlike the latter, a meta-analysis compares and evaluates a defined number of similar studies. It is quantitative in nature and can help assess contrasting study findings.

Tips for writing a good review article

Here are a few practices that can make the time-consuming process of writing a review article easier:

• Define your question: Take your time to identify the research question and carefully articulate the topic of your review paper. A good review should also add something new to the field in terms of a hypothesis, inference, or conclusion. A carefully defined scientific question will give you more clarity in determining the novelty of your inferences.
• Identify credible sources: Identify relevant as well as credible studies that you can base your review on, with the help of multiple databases or search engines. It is also a good idea to conduct another search once you have finished your article to avoid missing relevant studies published during the course of your writing.
• Take notes: A literature search involves extensive reading, which can make it difficult to recall relevant information subsequently. Therefore, make notes while conducting the literature search and note down the source references. This will ensure that you have sufficient information to start with when you finally get to writing.
• Describe the title, abstract, and introduction: A good starting point to begin structuring your review is by drafting the title, abstract, and introduction. Explicitly writing down what your review aims to address in the field will help shape the rest of your article.
• Be unbiased and critical: Evaluate every piece of evidence in a critical but unbiased manner. This will help you present a proper assessment and a critical discussion in your article.
• Include a good summary: End by stating the take-home message and identify the limitations of existing studies that need to be addressed through future studies.
• Ask for feedback: Ask a colleague to provide feedback on both the content and the language or tone of your article before you submit it.
• Check your journal’s guidelines: Some journals only publish reviews, while some only publish research articles. Further, all journals clearly indicate their aims and scope. Therefore, make sure to check the appropriateness of a journal before submitting your article.

Writing review articles, especially systematic reviews or meta-analyses, can seem like a daunting task. However, Elsevier Author Services can guide you by providing useful tips on how to write an impressive review article that stands out and gets published!

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A Step-by-Step Guide to Writing a Scientific Review Article

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Manisha Bahl, A Step-by-Step Guide to Writing a Scientific Review Article, Journal of Breast Imaging , Volume 5, Issue 4, July/August 2023, Pages 480–485, https://doi.org/10.1093/jbi/wbad028

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Scientific review articles are comprehensive, focused reviews of the scientific literature written by subject matter experts. The task of writing a scientific review article can seem overwhelming; however, it can be managed by using an organized approach and devoting sufficient time to the process. The process involves selecting a topic about which the authors are knowledgeable and enthusiastic, conducting a literature search and critical analysis of the literature, and writing the article, which is composed of an abstract, introduction, body, and conclusion, with accompanying tables and figures. This article, which focuses on the narrative or traditional literature review, is intended to serve as a guide with practical steps for new writers. Tips for success are also discussed, including selecting a focused topic, maintaining objectivity and balance while writing, avoiding tedious data presentation in a laundry list format, moving from descriptions of the literature to critical analysis, avoiding simplistic conclusions, and budgeting time for the overall process.

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How to write a good scientific review article

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• 1 The FEBS Journal Editorial Office, Cambridge, UK.
• PMID: 35792782
• DOI: 10.1111/febs.16565

Literature reviews are valuable resources for the scientific community. With research accelerating at an unprecedented speed in recent years and more and more original papers being published, review articles have become increasingly important as a means to keep up to date with developments in a particular area of research. A good review article provides readers with an in-depth understanding of a field and highlights key gaps and challenges to address with future research. Writing a review article also helps to expand the writer's knowledge of their specialist area and to develop their analytical and communication skills, amongst other benefits. Thus, the importance of building review-writing into a scientific career cannot be overstated. In this instalment of The FEBS Journal's Words of Advice series, I provide detailed guidance on planning and writing an informative and engaging literature review.

© 2022 Federation of European Biochemical Societies.

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How to write a review article?

In the medical sciences, the importance of review articles is rising. When clinicians want to update their knowledge and generate guidelines about a topic, they frequently use reviews as a starting point. The value of a review is associated with what has been done, what has been found and how these findings are presented. Before asking ‘how,’ the question of ‘why’ is more important when starting to write a review. The main and fundamental purpose of writing a review is to create a readable synthesis of the best resources available in the literature for an important research question or a current area of research. Although the idea of writing a review is attractive, it is important to spend time identifying the important questions. Good review methods are critical because they provide an unbiased point of view for the reader regarding the current literature. There is a consensus that a review should be written in a systematic fashion, a notion that is usually followed. In a systematic review with a focused question, the research methods must be clearly described. A ‘methodological filter’ is the best method for identifying the best working style for a research question, and this method reduces the workload when surveying the literature. An essential part of the review process is differentiating good research from bad and leaning on the results of the better studies. The ideal way to synthesize studies is to perform a meta-analysis. In conclusion, when writing a review, it is best to clearly focus on fixed ideas, to use a procedural and critical approach to the literature and to express your findings in an attractive way.

The importance of review articles in health sciences is increasing day by day. Clinicians frequently benefit from review articles to update their knowledge in their field of specialization, and use these articles as a starting point for formulating guidelines. [ 1 , 2 ] The institutions which provide financial support for further investigations resort to these reviews to reveal the need for these researches. [ 3 ] As is the case with all other researches, the value of a review article is related to what is achieved, what is found, and the way of communicating this information. A few studies have evaluated the quality of review articles. Murlow evaluated 50 review articles published in 1985, and 1986, and revealed that none of them had complied with clear-cut scientific criteria. [ 4 ] In 1996 an international group that analyzed articles, demonstrated the aspects of review articles, and meta-analyses that had not complied with scientific criteria, and elaborated QUOROM (QUality Of Reporting Of Meta-analyses) statement which focused on meta-analyses of randomized controlled studies. [ 5 ] Later on this guideline was updated, and named as PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). [ 6 ]

Review articles are divided into 2 categories as narrative, and systematic reviews. Narrative reviews are written in an easily readable format, and allow consideration of the subject matter within a large spectrum. However in a systematic review, a very detailed, and comprehensive literature surveying is performed on the selected topic. [ 7 , 8 ] Since it is a result of a more detailed literature surveying with relatively lesser involvement of author’s bias, systematic reviews are considered as gold standard articles. Systematic reviews can be diivded into qualitative, and quantitative reviews. In both of them detailed literature surveying is performed. However in quantitative reviews, study data are collected, and statistically evaluated (ie. meta-analysis). [ 8 ]

Before inquring for the method of preparation of a review article, it is more logical to investigate the motivation behind writing the review article in question. The fundamental rationale of writing a review article is to make a readable synthesis of the best literature sources on an important research inquiry or a topic. This simple definition of a review article contains the following key elements:

• The question(s) to be dealt with
• Methods used to find out, and select the best quality researches so as to respond to these questions.
• To synthetize available, but quite different researches

For the specification of important questions to be answered, number of literature references to be consulted should be more or less determined. Discussions should be conducted with colleagues in the same area of interest, and time should be reserved for the solution of the problem(s). Though starting to write the review article promptly seems to be very alluring, the time you spend for the determination of important issues won’t be a waste of time. [ 9 ]

The PRISMA statement [ 6 ] elaborated to write a well-designed review articles contains a 27-item checklist ( Table 1 ). It will be reasonable to fulfill the requirements of these items during preparation of a review article or a meta-analysis. Thus preparation of a comprehensible article with a high-quality scientific content can be feasible.

PRISMA statement: A 27-item checklist

Contents and format

Important differences exist between systematic, and non-systematic reviews which especially arise from methodologies used in the description of the literature sources. A non-systematic review means use of articles collected for years with the recommendations of your colleagues, while systematic review is based on struggles to search for, and find the best possible researches which will respond to the questions predetermined at the start of the review.

Though a consensus has been reached about the systematic design of the review articles, studies revealed that most of them had not been written in a systematic format. McAlister et al. analyzed review articles in 6 medical journals, and disclosed that in less than one fourth of the review articles, methods of description, evaluation or synthesis of evidence had been provided, one third of them had focused on a clinical topic, and only half of them had provided quantitative data about the extend of the potential benefits. [ 10 ]

Use of proper methodologies in review articles is important in that readers assume an objective attitude towards updated information. We can confront two problems while we are using data from researches in order to answer certain questions. Firstly, we can be prejudiced during selection of research articles or these articles might be biased. To minimize this risk, methodologies used in our reviews should allow us to define, and use researches with minimal degree of bias. The second problem is that, most of the researches have been performed with small sample sizes. In statistical methods in meta-analyses, available researches are combined to increase the statistical power of the study. The problematic aspect of a non-systematic review is that our tendency to give biased responses to the questions, in other words we apt to select the studies with known or favourite results, rather than the best quality investigations among them.

As is the case with many research articles, general format of a systematic review on a single subject includes sections of Introduction, Methods, Results, and Discussion ( Table 2 ).

Structure of a systematic review

Preparation of the review article

Steps, and targets of constructing a good review article are listed in Table 3 . To write a good review article the items in Table 3 should be implemented step by step. [ 11 – 13 ]

Steps of a systematic review

The research question

It might be helpful to divide the research question into components. The most prevalently used format for questions related to the treatment is PICO (P - Patient, Problem or Population; I-Intervention; C-appropriate Comparisons, and O-Outcome measures) procedure. For example In female patients (P) with stress urinary incontinence, comparisons (C) between transobturator, and retropubic midurethral tension-free band surgery (I) as for patients’ satisfaction (O).

Finding Studies

In a systematic review on a focused question, methods of investigation used should be clearly specified.

Ideally, research methods, investigated databases, and key words should be described in the final report. Different databases are used dependent on the topic analyzed. In most of the clinical topics, Medline should be surveyed. However searching through Embase and CINAHL can be also appropriate.

While determining appropriate terms for surveying, PICO elements of the issue to be sought may guide the process. Since in general we are interested in more than one outcome, P, and I can be key elements. In this case we should think about synonyms of P, and I elements, and combine them with a conjunction AND.

One method which might alleviate the workload of surveying process is “methodological filter” which aims to find the best investigation method for each research question. A good example of this method can be found in PubMed interface of Medline. The Clinical Queries tool offers empirically developed filters for five different inquiries as guidelines for etiology, diagnosis, treatment, prognosis or clinical prediction.

Evaluation of the Quality of the Study

As an indispensable component of the review process is to discriminate good, and bad quality researches from each other, and the outcomes should be based on better qualified researches, as far as possible. To achieve this goal you should know the best possible evidence for each type of question The first component of the quality is its general planning/design of the study. General planning/design of a cohort study, a case series or normal study demonstrates variations.

A hierarchy of evidence for different research questions is presented in Table 4 . However this hierarchy is only a first step. After you find good quality research articles, you won’t need to read all the rest of other articles which saves you tons of time. [ 14 ]

Determination of levels of evidence based on the type of the research question

Formulating a Synthesis

Rarely all researches arrive at the same conclusion. In this case a solution should be found. However it is risky to make a decision based on the votes of absolute majority. Indeed, a well-performed large scale study, and a weakly designed one are weighed on the same scale. Therefore, ideally a meta-analysis should be performed to solve apparent differences. Ideally, first of all, one should be focused on the largest, and higher quality study, then other studies should be compared with this basic study.

Conclusions

In conclusion, during writing process of a review article, the procedures to be achieved can be indicated as follows: 1) Get rid of fixed ideas, and obsessions from your head, and view the subject from a large perspective. 2) Research articles in the literature should be approached with a methodological, and critical attitude and 3) finally data should be explained in an attractive way.

Review Paper Format: How To Write A Review Article Fast

This guide aims to demystify the review paper format, presenting practical tips to help you accelerate the writing process. 

From understanding the structure to synthesising literature effectively, we’ll explore how to create a compelling review article swiftly, ensuring your work is both impactful and timely.

Whether you’re a seasoned researcher or a budding scholar, these insights will streamline your writing journey.

Research Paper, Review Paper Format

What is a review paper.

Diving into the realm of scholarly communication, you might have stumbled upon a research review article.

This unique genre serves to synthesise existing data, offering a panoramic view of the current state of knowledge on a particular topic. 

Unlike a standard research article that presents original experiments, a review paper delves into published literature, aiming to: 

• clarify, and
• evaluate previous findings.

Imagine you’re tasked to write a review article. The starting point is often a burning research question. Your mission? To scour various journals, piecing together a well-structured narrative that not only summarises key findings but also identifies gaps in existing literature.

This is where the magic of review writing shines – it’s about creating a roadmap for future research, highlighting areas ripe for exploration.

Review articles come in different flavours, with systematic reviews and meta-analyses being the gold standards. The methodology here is meticulous, with a clear protocol for selecting and evaluating studies.

This rigorous approach ensures that your review is more than just an overview; it’s a critical analysis that adds depth to the understanding of the subject.

Crafting a good review requires mastering the art of citation. Every claim or observation you make needs to be backed by relevant literature. This not only lends credibility to your work but also provides a treasure trove of information for readers eager to delve deeper.

Types Of Review Paper

Not all review articles are created equal. Each type has its methodology, purpose, and format, catering to different research needs and questions.

Systematic Review Paper

First up is the systematic review, the crème de la crème of review types. It’s known for its rigorous methodology, involving a detailed plan for:

• identifying,
• selecting, and
• critically appraising relevant research. 

The aim? To answer a specific research question. Systematic reviews often include meta-analyses, where data from multiple studies are statistically combined to provide more robust conclusions. This review type is a cornerstone in evidence-based fields like healthcare.

Literature Review Paper

Then there’s the literature review, a broader type you might encounter.

Here, the goal is to give an overview of the main points and debates on a topic, without the stringent methodological framework of a systematic review.

Literature reviews are great for getting a grasp of the field and identifying where future research might head. Often reading literature review papers can help you to learn about a topic rather quickly.

Narrative Reviews

Narrative reviews allow for a more flexible approach. Authors of narrative reviews draw on existing literature to provide insights or critique a certain area of research.

This is generally done with a less formal structure than systematic reviews. This type is particularly useful for areas where it’s difficult to quantify findings across studies.

Scoping Reviews

Scoping reviews are gaining traction for their ability to map out the existing literature on a broad topic, identifying:

• key concepts,
• theories, and

Unlike systematic reviews, scoping reviews have a more exploratory approach, which can be particularly useful in emerging fields or for topics that haven’t been comprehensively reviewed before.

Each type of review serves a unique purpose and requires a specific skill set. Whether you’re looking to summarise existing findings, synthesise data for evidence-based practice, or explore new research territories, there’s a review type that fits the bill. 

Knowing how to write, read, and interpret these reviews can significantly enhance your understanding of any research area.

What Are The Parts In A Review Paper

A review paper has a pretty set structure, with minor changes here and there to suit the topic covered. The format not only organises your thoughts but also guides your readers through the complexities of your topic.

Title & Abstract

Starting with the title and abstract, you set the stage. The title should be a concise indicator of the content, making it easier for others to quickly tell what your article content is about.

As for the abstract, it should act as a descriptive summary, offering a snapshot of your review’s scope and findings. 

Introduction

The introduction lays the groundwork, presenting the research question that drives your review. It’s here you:

• justify the importance of your review,
• delineating the current state of knowledge and
• highlighting gaps.

This section aims to articulate the significance of the topic and your objective in exploring it.

Methodology

The methodology section is the backbone of systematic reviews and meta-analyses, detailing the research methods employed to select, assess, and synthesise studies. 

This transparency allows readers to gauge the rigour and reproducibility of your review. It’s a testament to the integrity of your work, showing how you’ve minimised bias.

The heart of your review lies in the body, where you:

• analyse, and
• critique existing literature.

This is where you synthesise evidence, draw connections, and present both sides of any argument. Well-structured paragraphs and clear subheadings guide readers through your analysis, offering insights and fostering a deeper understanding of the subject.

Discussion & Conclusion

The discussion or conclusion section is where you weave together the main points, reflecting on what your findings mean for the field.

It’s about connecting the dots, offering a synthesis of evidence that answers your initial research question. This part often hints at future research directions, suggesting areas that need further exploration due to gaps in existing knowledge.

Lastly, the citation list is your nod to the scholarly community, acknowledging the contributions of others. Each citation is a thread in the larger tapestry of academic discourse, enabling readers to delve deeper into the research that has shaped your review.

Tips To Write An Review Article Fast

Writing a review article quickly without sacrificing quality might seem like a tall order, but with the right approach, it’s entirely achievable. 

Clearly Define Your Research Question

Clearly define your research question. A focused question not only narrows down the scope of your literature search but also keeps your review concise and on track.

By honing in on a specific aspect of a broader topic, you can avoid the common pitfall of becoming overwhelmed by the vast expanse of available literature. This specificity allows you to zero in on the most relevant studies, making your review more impactful.

Efficient Literature Searching

Utilise databases specific to your field and employ advanced search techniques like Boolean operators. This can drastically reduce the time you spend sifting through irrelevant articles.

Additionally, leveraging citation chains—looking at who has cited a pivotal paper in your area and who it cites—can uncover valuable sources you might otherwise miss.

Organise Your Findings Systematically

Developing a robust organisation strategy is key. As you gather sources, categorize them based on themes or methodologies. This not only aids in structuring your review but also in identifying areas where research is lacking or abundant.

Tools like citation management software can be invaluable here, helping you keep track of your sources and their key points. We list out some of the best AI tools for academic research here. 

Build An Outline Before Writing

Don’t underestimate the power of a well-structured outline. A clear blueprint of your article can guide your writing process, ensuring that each section flows logically into the next.

This roadmap not only speeds up the writing process by providing a clear direction but also helps maintain coherence, ensuring your review article delivers a compelling narrative that advances understanding in your field.

Start Writing With The Easiest Sections

When it’s time to write, start with sections you find easiest. This might be the methodology or a particular thematic section where you feel most confident.

Getting words on the page can build momentum, making it easier to tackle more challenging sections later.

Remember, your first draft doesn’t have to be perfect; the goal is to start articulating your synthesis of the literature.

Learn How To Write An Article Review

Mastering the review paper format is a crucial step towards efficient academic writing. By adhering to the structured components outlined, you can streamline the creation of a compelling review article.

Embracing these guidelines not only speeds up the writing process but also enhances the clarity and impact of your work, ensuring your contributions to scholarly discourse are both valuable and timely.

Dr Andrew Stapleton has a Masters and PhD in Chemistry from the UK and Australia. He has many years of research experience and has worked as a Postdoctoral Fellow and Associate at a number of Universities. Although having secured funding for his own research, he left academia to help others with his YouTube channel all about the inner workings of academia and how to make it work for you.

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Reviewing review articles

A review article is written to summarize the current state of understanding on a topic, and peer reviewing these types of articles requires a slightly different set of criteria compared with empirical articles. Unless it is a systematic review/meta-analysis methods are not important or reported. The quality of a review article can be judged on aspects such as timeliness, the breadth and accuracy of the discussion, and if it indicates the best avenues for future research. The review article should present an unbiased summary of the current understanding of the topic, and therefore the peer reviewer must assess the selection of studies that are cited by the paper. As review article contains a large amount of detailed information, its structure and flow are also important.

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Writing a Literature Review

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A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

• An introductory paragraph that explains what your working topic and thesis is
• A forecast of key topics or texts that will appear in the review
• Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
• Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically Evaluate: Mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

• Summarize the key findings you have taken from the literature and emphasize their significance
• Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

• Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
• Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
• Qualitative versus quantitative research
• Empirical versus theoretical scholarship
• Divide the research by sociological, historical, or cultural sources
• Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

• It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
• Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
• Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
• Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

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Title: differentially private federated learning: a systematic review.

Abstract: In recent years, privacy and security concerns in machine learning have promoted trusted federated learning to the forefront of research. Differential privacy has emerged as the de facto standard for privacy protection in federated learning due to its rigorous mathematical foundation and provable guarantee. Despite extensive research on algorithms that incorporate differential privacy within federated learning, there remains an evident deficiency in systematic reviews that categorize and synthesize these studies. Our work presents a systematic overview of the differentially private federated learning. Existing taxonomies have not adequately considered objects and level of privacy protection provided by various differential privacy models in federated learning. To rectify this gap, we propose a new taxonomy of differentially private federated learning based on definition and guarantee of various differential privacy models and federated scenarios. Our classification allows for a clear delineation of the protected objects across various differential privacy models and their respective neighborhood levels within federated learning environments. Furthermore, we explore the applications of differential privacy in federated learning scenarios. Our work provide valuable insights into privacy-preserving federated learning and suggest practical directions for future research.

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• Published: 16 May 2024

The Egyptian pyramid chain was built along the now abandoned Ahramat Nile Branch

• Eman Ghoneim   ORCID: orcid.org/0000-0003-3988-0335 1 ,
• Timothy J. Ralph   ORCID: orcid.org/0000-0002-4956-606X 2 ,
• Suzanne Onstine 3 ,
• Raghda El-Behaedi 4 ,
• Gad El-Qady 5 ,
• Amr S. Fahil 6 ,
• Mahfooz Hafez 5 ,
• Magdy Atya 5 ,
• Mohamed Ebrahim   ORCID: orcid.org/0000-0002-4068-5628 5 ,
• Ashraf Khozym 5 &
• Mohamed S. Fathy 6  

Communications Earth & Environment volume  5 , Article number:  233 ( 2024 ) Cite this article

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• Archaeology
• Geomorphology
• Hydrogeology
• Sedimentology

The largest pyramid field in Egypt is clustered along a narrow desert strip, yet no convincing explanation as to why these pyramids are concentrated in this specific locality has been given so far. Here we use radar satellite imagery, in conjunction with geophysical data and deep soil coring, to investigate the subsurface structure and sedimentology in the Nile Valley next to these pyramids. We identify segments of a major extinct Nile branch, which we name The Ahramat Branch, running at the foothills of the Western Desert Plateau, where the majority of the pyramids lie. Many of the pyramids, dating to the Old and Middle Kingdoms, have causeways that lead to the branch and terminate with Valley Temples which may have acted as river harbors along it in the past. We suggest that The Ahramat Branch played a role in the monuments’ construction and that it was simultaneously active and used as a transportation waterway for workmen and building materials to the pyramids’ sites.

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Introduction.

The landscape of the northern Nile Valley in Egypt, between Lisht in the south and the Giza Plateau in the north, was subject to a number of environmental and hydrological changes during the past few millennia 1 , 2 . In the Early Holocene (~12,000 years before present), the Sahara of North Africa transformed from a hyper-arid desert to a savannah-like environment, with large river systems and lake basins 3 , 4 due to an increase in global sea level at the end of the Last Glacial Maximum (LGM). The wet conditions of the Sahara provided a suitable habitat for people and wildlife, unlike in the Nile Valley, which was virtually inhospitable to humans because of the constantly higher river levels and swampy environment 5 . At this time, Nile River discharge was high, which is evident from the extensive deposition of organic-rich fluvial sediment in the Eastern Mediterranean basin 6 . Based on the interpretation of archeological material and pollen records, this period, known as the African Humid Period (AHP) (ca. 14,500–5000 years ago), was the most significant and persistent wet period from the early to mid-Holocene in the eastern Sahara region 7 , with an annual rainfall rate of 300–920 mm yr −1   8 . During this time the Nile would have had several secondary channels branching across the floodplain, similar to those described by early historians (e.g., Herodotus).

During the mid-Holocene (~10,000–6000 years ago), freshwater marshes were common within the Nile floodplain causing habitation to be more nucleated along the desert margins of the Nile Valley 9 . The desert margins provided a haven from the high Nile water. With the ending of the AHP and the beginning of the Late Holocene (~5500 years ago to present), rainfall greatly declined, and the region’s humid phase gradually came to an end with punctuated short wet episodes 10 . Due to increased aridity in the Sahara, more people moved out of the desert towards the Nile Valley and settled along the edge of the Nile floodplain. With the reduced precipitation, sedimentation increased in and around the Nile River channels causing the proximal floodplain to rise in height and adjacent marshland to decrease in the area 11 , 12 estimated the Nile flood levels to have ranged from 1 to 4 m above the baseline (~5000 BP). Inhabitants moved downhill to the Nile Valley and settled in the elevated areas on the floodplain, including the raised natural levees of the river and jeziras (islands). This was the beginning of the Old Kingdom Period (ca. 2686 BCE) and the time when early pyramid complexes, including the Step Pyramid of Djoser, were constructed at the margins of the floodplain. During this time the Nile discharge was still considerably higher than its present level. The high flow of the river, particularly during the short-wet intervals, enabled the Nile to maintain multiple branches, which meandered through its floodplain. Although the landscape of the Nile floodplain has greatly transformed due to river regulation associated with the construction of the Aswan High Dam in the 1960s, this region still retains some clear hydro-geomorphological traces of the abandoned river channels.

Since the beginning of the Pharaonic era, the Nile River has played a fundamental role in the rapid growth and expansion of the Egyptian civilization. Serving as their lifeline in a largely arid landscape, the Nile provided sustenance and functioned as the main water corridor that allowed for the transportation of goods and building materials. For this reason, most of the key cities and monuments were in close proximity to the banks of the Nile and its peripheral branches. Over time, however, the main course of the Nile River laterally migrated, and its peripheral branches silted up, leaving behind many ancient Egyptian sites distant from the present-day river course 9 , 13 , 14 , 15 . Yet, it is still unclear as to where exactly the ancient Nile courses were situated 16 , and whether different reaches of the Nile had single or multiple branches that were simultaneously active in the past. Given the lack of consensus amongst scholars regarding this subject, it is imperative to develop a comprehensive understanding of the Nile during the time of the ancient Egyptian civilization. Such a poor understanding of Nile River morphodynamics, particularly in the region that hosts the largest pyramid fields of Egypt, from Lisht to Giza, limits our understanding of how changes in the landscape influenced human activities and settlement patterns in this region, and significantly restricts our ability to understand the daily lives and stories of the ancient Egyptians.

Currently, much of the original surface of the ancient Nile floodplain is masked by either anthropogenic activity or broad silt and sand sheets. For this reason, singular approaches such as on-ground searches for the remains of hidden former Nile branches are both increasingly difficult and inauspicious. A number of studies have already been carried out in Egypt to locate segments of the ancient Nile course. For instance 9 , proposed that the axis of the Nile River ran far west of its modern course past ancient cities such as el-Ashmunein (Hermopolis) 13 . mapped the ancient hydrological landscape in the Luxor area and estimated both an eastward and westward Nile migration rate of 2–3 km per 1000 years. In the Nile Delta region 17 , detected several segments of buried Nile distributaries and elevated mounds using geoelectrical resistivity surveys. Similarly, a study by Bunbury and Lutley 14 identified a segment of an ancient Nile channel, about 5000 years old, near the ancient town of Memphis ( men-nefer ). More recently 15 , used cores taken around Memphis to reveal a section of a lateral ancient Nile branch that was dated to the Neolithic and Predynastic times (ca. 7000–5000 BCE). On the bank of this branch, Memphis, the first capital of unified Egypt, was founded in early Pharaonic times. Over the Dynastic period, this lateral branch then significantly migrated eastwards 15 . A study by Toonen et al. 18 , using borehole data and electrical resistivity tomography, further revealed a segment of an ancient Nile branch, dating to the New Kingdom Period, situated near the desert edge west of Luxor. This river branch would have connected important localities and thus played a significant role in the cultural landscape of this area. More recent research conducted further north by Sheisha et al. 2 , near the Giza Plateau, indicated the presence of a former river and marsh-like environment in the floodplain east of the three great Pyramids of Giza.

Even though the largest concentration of pyramids in Egypt are located along a narrow desert strip from south Lisht to Giza, no explanation has been offered as to why these pyramid fields were condensed in this particular area. Monumental structures, such as pyramids and temples, would logically be built near major waterways to facilitate the transportation of their construction materials and workers. Yet, no waterway has been found near the largest pyramid field in Egypt, with the Nile River lying several kilometers away. Even though many efforts to reconstruct the ancient Nile waterways have been conducted, they have largely been confined to small sites, which has led to the mapping of only fragmented sections of the ancient Nile channel systems.

In this work, we present remote sensing, geomorphological, soil coring and geophysical evidence to support the existence of a long-lost ancient river branch, the Ahramat Branch, and provide the first map of the paleohydrological setting in the Lisht-Giza area. The finding of the Ahramat Branch is not only crucial to our understanding of why the pyramids were built in these specific geographical areas, but also for understanding how the pyramids were accessed and constructed by the ancient population. It has been speculated by many scholars that the ancient Egyptians used the Nile River for help transporting construction materials to pyramid building sites, but until now, this ancient Nile branch was not fully uncovered or mapped. This work can help us better understand the former hydrological setting of this region, which would in turn help us learn more about the environmental parameters that may have influenced the decision to build these pyramids in their current locations during the time of Pharaonic Egypt.

Position and morphology of the Ahramat Branch

Synthetic Aperture Radar (SAR) imagery and radar high-resolution elevation data for the Nile floodplain and its desert margins, between south Lisht and the Giza Plateau area, provide evidence for the existence of segments of a major ancient river branch bordering 31 pyramids dating from the Old Kingdom to Second Intermediate Period (2686−1649 BCE) and spanning between Dynasties 3–13 (Fig.  1a ). This extinct branch is referred to hereafter as the Ahramat Branch, meaning the “Pyramids Branch” in Arabic. Although masked by the cultivated fields of the Nile floodplain, subtle topographic expressions of this former branch, now invisible in optical satellite data, can be traced on the ground surface by TanDEM-X (TDX) radar data and the Topographic Position Index (TPI). Data analysis indicates that this lateral distributary channel lies between 2.5 and 10.25 km west from the modern Nile River. The branch appears to have a surface channel depth between 2 and 8 m, a channel length of about 64 km and a channel width of 200–700 m, which is similar to the width of the contemporary neighboring Nile course. The size and longitudinal continuity of the Ahramat Branch and its proximity to all the pyramids in the study area implies a functional waterway of great significance.

a Shows the Ahramat Branch borders a large number of pyramids dating from the Old Kingdom to the 2 nd Intermediate Period and spanning between Dynasties 3 and 13. b Shows Bahr el-Libeini canal and remnant of abandoned channel visible in the 1911 historical map (Egyptian Survey Department scale 1:50,000). c Bahr el-Libeini canal and the abandoned channel are overlain on satellite basemap. Bahr el-Libeini is possibly the last remnant of the Ahramat Branch before it migrated eastward. d A visible segment of the Ahramat Branch in TDX is now partially occupied by the modern Bahr el-Libeini canal. e A major segment of the Ahramat Branch, approximately 20 km long and 0.5 km wide, can be traced in the floodplain along the Western Desert Plateau south of the town of Jirza. Location of e is marked in white a box in a . (ESRI World Image Basemap, source: Esri, Maxar, Earthstar Geographics).

A trace of a 3 km river segment of the Ahramat Branch, with a width of about 260 m, is observable in the floodplain west of the Abu Sir pyramids field (Fig.  1b–d ). Another major segment of the Ahramat Branch, approximately 20 km long and 0.5 km wide can be traced in the floodplain along the Western Desert Plateau south of the town of Jirza (Fig.  1e ). The visible segments of the Ahramat Branch in TDX are now partially occupied by the modern Bahr el-Libeini canal. Such partial overlap between the courses of this canal, traced in the1911 historical maps (Egyptian Survey Department scale 1:50,000), and the Ahramat Branch is clear in areas where the Nile floodplain is narrower (Fig.  1b–d ), while in areas where the floodplain gets wider, the two water courses are about 2 km apart. In light of that, Bahr el-Libeini canal is possibly the last remnant of the Ahramat Branch before it migrated eastward, silted up, and vanished. In the course of the eastward migration over the Nile floodplain, the meandering Ahramat Branch would have left behind traces of abandoned channels (narrow oxbow lakes) which formed as a result of the river erosion through the neck of its meanders. A number of these abandoned channels can be traced in the 1911 historical maps near the foothill of the Western Desert plateau proving the eastward shifting of the branch at this locality (Fig.  1b–d ). The Dahshur Lake, southwest of the city of Dahshur, is most likely the last existing trace of the course of the Ahramat Branch.

Subsurface structure and sedimentology of the Ahramat Branch

Geophysical surveys using Ground Penetrating Radar (GPR) and Electromagnetic Tomography (EMT) along a 1.2 km long profile revealed a hidden river channel lying 1–1.5 m below the cultivated Nile floodplain (Fig.  2 ). The position and shape of this river channel is in an excellent match with those derived from radar satellite imagery for the Ahramat Branch. The EMT profile shows a distinct unconformity in the middle, which in this case indicates sediments that have a different texture than the overlying recent floodplain silt deposits and the sandy sediments that are adjacent to this former branch (Fig.  2 ). GPR overlapping the EMT profile from 600–1100 m on the transect confirms this. Here, we see evidence of an abandoned riverbed approximately 400 m wide and at least 25 m deep (width:depth ratio ~16) at this location. This branch has a symmetrical channel shape and has been infilled with sandy Neonile sediment different to other surrounding Neonile deposits and the underlying Eocene bedrock. The geophysical profile interpretation for the Ahramat Branch at this locality was validated using two sediment cores of depths 20 m (Core A) and 13 m (Core B) (Fig.  3 ). In Core A between the center and left bank of the former branch we found brown sandy mud at the floodplain surface and down to ~2.7 m with some limestone and chert fragments, a reddish sandy mud layer with gravel and handmade material inclusions at ~2.8 m, a gray sandy mud layer from ~3–5.8 m, another reddish sandy mud layer with gravel and freshwater mussel shells at ~6 m, black sandy mud from ~6–8 m, and sandy silt grading into clean, well-sorted medium sand dominated the profile from ~8 to >13 m. In Core B on the right bank of the former branch we found recently deposited brown sandy mud at the floodplain surface and down to ~1.5 m, alternating brown and gray layers of silty and sandy mud down to ~4 m (some reddish layers with gravel and handmade material inclusions), a black sandy mud layer from ~4–4.9 m, and another reddish sandy mud layer with gravel and freshwater mussel shells at ~5 m, before clean, well-sorted medium sand dominated the profile from 5 to >20 m. Shallow groundwater was encountered in both cores concurrently with the sand layers, indicating that the buried sedimentary structure of the abandoned Ahramat Branch acts as a conduit for subsurface water flow beneath the distal floodplain of the modern Nile River.

a Locations of geophysical profile and soil drilling (ESRI World Image Basemap, source: Esri, Maxar, Earthstar Geographics). Photos taken from the field while using the b Electromagnetic Tomography (EMT) and c Ground Penetrating Radar (GPR). d Showing the apparent conductivity profile, e showing EMT profile, and f showing GPR profiles with overlain sketch of the channel boundary on the GPR graph. g Simplified interpretation of the buried channel with the location of the two-soil coring of A and B.

It shows two-soil cores, A and core B, with soil profile descriptions, graphic core logs, sediment grain size charts, and example photographs.

Alignment of old and middle kingdom pyramids to the Ahramat Branch

The royal pyramids in ancient Egypt are not isolated monuments, but rather joined with several other structures to form complexes. Besides the pyramid itself, the pyramid complex includes the mortuary temple next to the pyramid, a valley temple farther away from the pyramid on the edge of a waterbody, and a long sloping causeway that connects the two temples. A causeway is a ceremonial raised walkway, which provides access to the pyramid site and was part of the religious aspects of the pyramid itself 19 . In the study area, it was found that many of the causeways of the pyramids run perpendicular to the course of the Ahramat Branch and terminate directly on its riverbank.

In Egyptian pyramid complexes, the valley temples at the end of causeways acted as river harbors. These harbors served as an entry point for the river borne visitors and ceremonial roads to the pyramid. Countless valley temples in Egypt have not yet been found and, therefore, might still be buried beneath the agricultural fields and desert sands along the riverbank of the Ahramat Branch. Five of these valley temples, however, partially survived and still exist in the study area. These temples include the valley temples of the Bent Pyramid, the Pyramid of Khafre, and the Pyramid of Menkaure from Dynasty 4; the valley temple of the Pyramid of Sahure from Dynasty 5, and the valley temple of the Pyramid of Pepi II from Dynasty 6. All the aforementioned temples are dated to the Old Kingdom. These five surviving temples were found to be positioned adjacent to the riverbank of the Ahramat Branch, which strongly implies that this river branch was contemporaneously functioning during the Old Kingdom, at the time of pyramid construction.

Analysis of the ground elevation of the 31 pyramids and their proximity to the floodplain, within the study area, helped explain the position and relative water level of the Ahramat Branch during the time between the Old Kingdom and Second Intermediate Period (ca. 2649–1540 BCE). Based on Fig. ( 4) , the Ahramat Branch had a high-water level during the first part of the Old Kingdom, especially during Dynasty 4. This is evident from the high ground elevation and long distance from the floodplain of the pyramids dated to that period. For instance, the remote position of the Bent and Red Pyramids in the desert, very far from the Nile floodplain, is a testament to the branch’s high-water level. On the contrary, during the Old Kingdom, our data demonstrated that the Ahramat Branch would have reached its lowest level during Dynasty 5. This is evident from the low altitudes and close proximity to the floodplain of most Dynasty 5 pyramids. The orientation of the Sahure Pyramid’s causeway (Dynasty 5) and the location of its valley temple in the low-lying floodplain provide compelling evidence for the relatively low water level proposition of the Ahramat Branch during this stage. The water level of the Ahramat Branch would have been slightly raised by the end of Dynasty 5 (the last 15–30 years), during the reign of King Unas and continued to rise during Dynasty 6. The position of Pepi II and Merenre Pyramids (Dynasty 6) deep in the desert, west of the Djedkare Isesi Pyramid (Dynasty 5), supports this notion.

It explains the position and relative water level of the Ahramat Branch during the time between the Old Kingdom and Second Intermediate Period. a Shows positive correlation between the ground elevation of the pyramids and their proximity to the floodplain. b Shows positive correlation between the average ground elevation of the pyramids and their average proximity to the floodplain in each Dynasty. c Illustrates the water level interpretation by Hassan (1986) in Faiyum Lake in correlation to the average pyramids ground elevation and average distances to the floodplain in each Dynasty. d The data indicates that the Ahramat Branch had a high-water level during the first period of the Old Kingdom, especially during Dynasty 4. The water level reduced afterwards but was raised slightly in Dynasty 6. The position of the Middle Kingdom’s pyramids, which was at lower altitudes and in close proximity to the floodplain as compared to those of the Old Kingdom might be explained by the slight eastward migration of the Ahramat Branch.

In addition, our analysis in Fig. ( 4) , shows that the Qakare Ibi Pyramid of Dynasty 8 was constructed very close to the floodplain on very low elevation, which implies that the Nile water levels were very low at this time of the First Intermediate Period (2181–2055 BCE). This finding is in agreement with previous work conducted by Kitchen 20 which implies that the sudden collapse of the Old Kingdom in Egypt (after 4160 BCE) was largely caused by catastrophic failure of the annual flood of the Nile River for a period of 30–40 years. Data from soil cores near Memphis indicated that the Old Kingdom settlement is covered by about 3 m of sand 11 . Accordingly, the Ahramat Branch was initially positioned further west during the Old Kingdom and then shifted east during the Middle Kingdom due to the drought-induced sand encroachments of the First Intermediate Period, “a period of decentralization and weak pharaonic rule” in ancient Egypt, spanning about 125 years (2181–2055 BCE) post Old Kingdom era. Soil cores from the drilling program at Memphis show dominant dry conditions during the First Intermediate Period with massive eolian sand sheets extended over a distance of at least 0.5 km from the edge of the western desert escarpment 21 . The Ahramat Branch continued to move east during the Second Intermediate Period until it had gradually lost most of its water supply by the New Kingdom.

The western tributaries of the Ahramat Branch

Sentinal-1 radar data unveiled several wide channels (inlets) in the Western Desert Plateau connected to the Ahramat Branch. These inlets are currently covered by a layer of sand, thus partially invisible in multispectral satellite imagery. In Sentinal-1 radar imagery, the valley floors of these inlets appear darker than the surrounding surfaces, indicating subsurface fluvial deposits. These smooth deposits appear dark owing to the specular reflection of the radar signals away from the receiving antenna (Fig.  5a, b ) 22 . Considering that Sentinel-1’s C-Band has a penetration capability of approximately 50 cm in dry sand surface 23 , this would suggest that the riverbed of these channels is covered by at least half a meter of desert sand. Unlike these former inlets, the course of the Ahramat Branch is invisible in SAR data due in large part to the presence of dense farmlands in the floodplain, which limits radar penetration and the detection of underlying fluvial deposition. Moreover, the radar topographic data from TDX revealed the areal extent of these inlets. Their river courses were extracted from TDX data using the Topographic Position Index (TPI), an algorithm which is used to compute the topographic slope positions and to automate landform classifications (Fig.  5c, d ). Negative TPI values show the former riverbeds of the inlets, while positive TPI signify the riverbanks bordering them.

a Conceptual sketch of the dependence of surface roughness on the sensor wavelength λ (modified after 48 ). b Expected backscatter characteristics in sandy desert areas with buried dry riverbeds. c Dry channels/inlets masked by desert sand in the Dahshur area. d The channels’ courses were extracted using TPI. Negative TPI values highlight the courses of the channels while positive TPI signify their banks.

Analysis indicated that several of the pyramid’s causeways, from Dynasties 4 and 6, lead to the inlet’s riverbanks (Fig.  6 ). Among these pyramids, are the Bent Pyramid, the first pyramid built by King Snefru in Dynasty 4 and among the oldest, largest, and best preserved ancient Egyptian pyramids that predates the Giza Pyramids. This pyramid is situated at the royal necropolis of Dahshur. The position of the Bent Pyramid, deep in the desert, far from the modern Nile floodplain, remained unexplained by researchers. This pyramid has a long causeway (~700 m) that is paved in the desert with limestone blocks and is attached to a large valley temple. Although all the pyramids’ valley temples in Egypt are connected to a water body and served as the landing point of all the river-borne visitors, the valley temple of the Bent Pyramid is oddly located deep in the desert, very distant from any waterways and more than 1 km away from the western edge of the modern Nile floodplain. Radar data revealed that this temple overlooked the bank of one of these extinct channels (called Wadi al-Taflah in historical maps). This extinct channel (referred to hereafter as the Dahshur Inlet due to its geographical location) is more than 200 m wide on average (Fig.  6 ). In light of this finding, the Dahshur Inlet, and the Ahramat Branch, are thus strongly argued to have been active during Dynasty 4 and must have played an important role in transporting building materials to the Bent Pyramid site. The Dahshur Inlet could have also served the adjacent Red Pyramid, the second pyramid built by the same king (King Snefru) in the Dahshur area. Yet, no traces of a causeway nor of a valley temple has been found thus far for the Red Pyramid. Interestingly, pyramids in this site dated to the Middle Kingdom, including the Amenemhat III pyramid, also known as the Black Pyramid, White Pyramid, and Pyramid of Senusret III, are all located at least 1 km far to the east of the Dynasty 4 pyramids (Bent and Red) near the floodplain (Fig.  6 ), which once again supports the notion of the eastward shift of the Ahramat Branch after the Old Kingdom.

a The two inlets are presently covered by sand, thus invisible in optical satellite imagery. b Radar data, and c TDX topographic data reveal the riverbed of the Sakkara Inlet due to radar signals penetration capability in dry sand. b and c show the causeways of Pepi II and Merenre Pyramids, from Dynasty 6, leading to the Saqqara Inlet. The Valley Temple of Pepi II Pyramid overlooks the inlet riverbank, which indicates that the inlet, and thus Ahramat Branch, were active during Dynasty 6. d Radar data, and e TDX topographic data, reveal the riverbed of the Dahshur Inlet with the Bent Pyramid’s causeway of Dynasty 4 leading to the Inlet. The Valley Temple of the Bent Pyramid overlooks the riverbank of the Dahshur Inlet, which indicates that the inlet and the Ahramat Branch were active during Dynasty 4 of the Old Kingdom.

Radar satellite data revealed yet another sandy buried channel (tributary), about 6 km north of the Dahshur Inlet, to the west of the ancient city of Memphis. This former fluvial channel (referred to hereafter as the Saqqara Inlet due to its geographical location) connects to the Ahramat Branch with a broad river course of more than 600 m wide. Data shows that the causeways of the two pyramids of Pepi II and Merenre, situated at the royal necropolis of Saqqara and dated to Dynasty 6, lead directly to the banks of the Saqqara Inlet (see Fig.  6 ). The 400 m long causeway of Pepi II pyramid runs northeast over the southern Saqqara plateau and connects to the riverbank of the Saqqara Inlet from the south. The causeway terminates with a valley temple that lies on the inlet’s riverbank. The 250 long causeway of the Pyramid of Merenre runs southeast over the northern Saqqara plateau and connects to the riverbank of the Saqqara Inlet from the north. Since both pyramids dated to Dynasty 6, it can be argued that the water level of the Ahramat Branch was higher during this period, which would have flooded at least the entrance of its western inlets. This indicates that the downstream segment of the Saqqara Inlet was active during Dynasty 6 and played a vital role in transporting construction materials and workers to the two pyramids sites. The fact that none of the Dynasty 5 pyramids in this area (e.g., the Djedkare Isesi Pyramid) were positioned on the Saqqara Inlet suggests that the water level in the Ahramat Branch was not high enough to enter and submerge its inlets during this period.

In addition, our data analysis clearly shows that the causeways of the Khafre, Menkaure, and Khentkaus pyramids, in the Giza Plateau, lead to a smaller but equally important river bay associated with the Ahramat Branch. This lagoon-like river arm is referred to here as the Giza Inlet (Fig.  7 ). The Khufu Pyramid, the largest pyramid in Egypt, seems to be connected directly to the river course of the Ahramat Branch (Fig.  7 ). This finding proves once again that the Ahramat Branch and its western inlets were hydrologically active during Dynasty 4 of the Old Kingdom. Our ancient river inlet hypothesis is also in accordance with earlier research, conducted on the Giza Plateau, which indicates the presence of a river and marsh-like environment in the floodplain east of the Giza pyramids 2 .

The causeways of the four Pyramids lead to an inlet, which we named the Giza Inlet, that connects from the west with the Ahramat Branch. These causeways connect the pyramids with valley temples which acted as river harbors in antiquity. These river segments are invisible in optical satellite imagery since they are masked by the cultivated lands of the Nile floodplain. The photo shows the valley temple of Khafre Pyramid (Photo source: Author Eman Ghoneim).

During the Old Kingdom Period, our analysis suggests that the Ahramat Branch had a high-water level during the first part, especially during Dynasty 4 whereas this water level was significantly decreased during Dynasty 5. This finding is in agreement with previous studies which indicate a high Nile discharge during Dynasty 4 (e.g., ref. 24 ). Sediment isotopic analysis of the Nile Delta indicated that Nile flows decrease more rapidly by the end of Dynasty 4 25 , in addition 26 reported that during Dynasties 5 and 6 the Nile flows were the lowest of the entire Dynastic period. This long-lost Ahramat Branch (possibly a former Yazoo tributary to the Nile) was large enough to carry a large volume of the Nile discharge in the past. The ancient channel segment uncovered by 1 , 15 west of the city of Memphis through borehole logs is most likely a small section of the large Ahramat Branch detected in this study. In the Middle Kingdom, although previous studies implied that the Nile witnessed abundant flood with occasional failures (e.g., ref. 27 ), our analysis shows that all the pyramids from the Middle Kingdom were built far east of their Old Kingdom counterparts, on lower altitudes and in close proximity to the floodplain as compared to those of the Old Kingdom. This paradox might be explained by the fact that the Ahramat Branch migrated eastward, slightly away from the Western Desert escarpment, prior to the construction of the Middle Kingdom pyramids, resulting in the pyramids being built eastward so that they could be near the waterway.

The eastward migration and abandonment of the Ahramat Branch could be attributed to gradual tilting of the Nile delta and floodplain in lower Egypt towards the northeast due to tectonic activity 28 . A topographic tilt such as this would have accelerated river movement eastward due to the river being located in the west at a relatively higher elevation of the floodplain. While near-channel floodplain deposition would naturally lead to alluvial ridge development around the active Ahramat Branch, and therefore to lower-lying tracts of adjacent floodplain to the east, regional tilting may explain the wholesale lateral migration of the river in that direction. The eastward migration and abandonment of the branch could also be ascribed to sand incursion due to the branch’s proximity to the Western Desert Plateau, where windblown sand is abundant. This would have increased sand deposition along the riverbanks and caused the river to silt up, particularly during periods of low flow. The region experienced drought during the First Intermediate Period, prior to the Middle Kingdom. In the area of Abu Rawash north 29 and Dahshur site 11 , settlements from the Early Dynastic and Old Kingdom were found to be covered by more than 3 m of desert sands. During this time, windblown sand engulfed the Old Kingdom settlements and desert sands extended eastward downhill over a distance of at least 0.5 km 21 . The abandonment of sites at Abusir (5 th Dynasty), where the early pottery-rich deposits are covered by wind-blown sand and then mud without sherds, can be used as evidence that the Ahramat Branch migrated eastward after the Old Kingdom. The increased sand deposition activity, during the end of the Old Kingdom, and throughout the First Intermediate Period, was most likely linked to the period of drought and desertification of the Sahara 30 . In addition, the reduced river discharge caused by decreased rainfall and increased aridity in the region would have gradually reduced the river course’s capacity, leading to silting and abandonment of the Ahramat Branch as the river migrated to the east.

The Dahshur, Saqqara, and Giza inlets, which were connected to the Ahramat Branch from the west, were remnants of past active drainage systems dated to the late Tertiary or the Pleistocene when rainwater was plentiful 31 . It is proposed that the downstream reaches of these former channels (wadis) were submerged during times of high-water levels of the Ahramat Branch, forming long narrow water arms (inlets) that gave a wedge-like shape to the western flank of the Ahramat Branch. During the Old Kingdom, the waters of these inlets would have flowed westward from the Ahramat Branch rather than from their headwaters. As the drought intensified during the First Intermediate Period, the water level of the Ahramat Branch was lowered and withdrew from its western inlets, causing them to silt up and eventually dry out. The Dahshur, Saqqara, and Giza inlets would have provided a bay environment where the water would have been calm enough for vessels and boats to dock far from the busy, open water of the Ahramat Branch.

Sediments from the Ahramat Branch riverbed, which were collected from the two deep soil cores (cores A and B), show an abrupt shift from well-sorted medium sands at depth to overlying finer materials with layers including gravel, shell, and handmade materials. This indicates a step-change from a relatively consistent higher-energy depositional regime to a generally lower-energy depositional regime with periodic flash floods at these sites. So, the Ahramat Branch in this region carried and deposited well-sorted medium sand during its last active phase, and over time became inactive, infilling with sand and mud until an abrupt change led the (by then) shallow depression fill with finer distal floodplain sediment (possibly in a wetland) that was utilized by people and experienced periodic flash flooding. Validation of the paleo-channel position and sediment type using these cores shows that the Ahramat Branch has similar morphological features and an upward-fining depositional sequence as that reported near Giza, where two cores were previously used to reconstruct late Holocene Nile floodplain paleo-environments 2 . Further deep soil coring could determine how consistent the geomorphological features are along the length of the Ahramat branch, and to help explain anomalies in areas where the branch has less surface expression and where remote sensing and geophysical techniques have limitations. Considering more core logs can give a better understanding of the floodplain and the buried paleo-channels.

The position of the Ahramat Branch along the western edge of the Nile floodplain suggests it to be the downstream extension of Bahr Yusef. In fact, Bahr Yusef’s course may have initially flowed north following the natural surface gradient of the floodplain before being forced to turn west to flow into the Fayum Depression. This assumption could be supported by the sharp westward bend of Bahr Yusef’s course at the entrance to the Fayum Depression, which could be a man-made attempt to change the waterflow direction of this branch. According to Römer 32 , during the Middle Kingdom, the Gadallah Dam located at the entrance of the Fayum, and a possible continuation running eastwards, blocked the flow of Bahr Yusef towards the north. However, a sluice, probably located near the village of el-Lahun, was created in order to better control the flow of water into the Fayum. When the sluice was locked, the water from Bahr Yusef was directed to the west and into the depression, and when the sluice was open, the water would flow towards the north via the course of the Ahramat Branch. Today, the abandoned Ahramat Branch north of Fayum appears to support subsurface water flow in the buried coarse sand bed layers, however these shallow groundwater levels are likely to be quite variable due to proximity of the bed layers to canals and other waterways that artificially maintain shallow groundwater. Groundwater levels in the region are known to be variable 33 , but data on shallow groundwater could be used to further validate the delineated paleo-channel of the Ahramat Branch.

The present work enabled the detection of segments of a major former Nile branch running at the foothills of the Western Desert Plateau, where the vast majority of the Ancient Egyptian pyramids lie. The enormity of this branch and its proximity to the pyramid complexes, in addition to the fact that the pyramids’ causeways terminate at its riverbank, all imply that this branch was active and operational during the construction phase of these pyramids. This waterway would have connected important locations in ancient Egypt, including cities and towns, and therefore, played an important role in the cultural landscape of the region. The eastward migration and abandonment of the Ahramat Branch could be attributed to gradual movement of the river to the lower-lying adjacent floodplain or tilting of the Nile floodplain toward the northeast as a result of tectonic activity, as well as windblown sand incursion due to the branch’s proximity to the Western Desert Plateau. The increased sand deposition was most likely related to periods of desertification of the Great Sahara in North Africa. In addition, the branch eastward movement and diminishing could be explained by the reduction of the river discharge and channel capacity caused by the decreased precipitation and increased aridity in the region, particularly during the end of the Old Kingdom.

The integration of radar satellite data with geophysical surveying and soil coring, which we utilized in this study, is a highly adaptable approach in locating similar former buried river systems in arid regions worldwide. Mapping the hidden course of the Ahramat Branch, allowed us to piece together a more complete picture of ancient Egypt’s former landscape and a possible water transportation route in Lower Egypt, in the area between Lisht and the Giza Plateau.

Revealing this extinct Nile branch can provide a more refined idea of where ancient settlements were possibly located in relation to it and prevent them from being lost to rapid urbanization. This could improve the protection measures of Egyptian cultural heritage. It is the hope that our findings can improve conservation measures and raise awareness of these sites for modern development planning. By understanding the landscape of the Nile floodplain and its environmental history, archeologists will be better equipped to prioritize locations for fieldwork investigation and, consequently, raise awareness of these sites for conservation purposes and modern development planning. Our finding has filled a much-needed knowledge gap related to the dominant waterscape in ancient Egypt, which could help inform and educate a wide array of global audiences about how earlier inhabitants were living and in what ways shifts in their landscape drove human activity in such an iconic region.

Materials and methods

The work comprised of two main elements: satellite remote sensing and historical maps and geophysical survey and sediment coring, complemented by archeological resources. Using this suite of investigative techniques provided insights into the nature and relationship of the former Ahramat Branch with the geographical location of the pyramid complexes in Egypt.

Satellite remote sensing and historical maps

Unlike optical sensors that image the land surface, radar sensors image the subsurface due to their unique ability to penetrate the ground and produce images of hidden paleo-rivers and structures. In this context, radar waves strip away the surface sand layer and expose previously unidentified buried channels. The penetration capability of radar waves in the hyper-arid regions of North Africa is well documented 4 , 34 , 35 , 36 , 37 . The penetration depth varies according to the radar wavelength used at the time of imaging. Radar signal penetration becomes possible without significant attenuation if the surface cover material is extremely dry (<1% moisture content), fine grained (<1/5 of the imaging wavelength) and physically homogeneous 23 . When penetrating desert sand, radar signals have the ability to detect subsurface soil roughness, texture, compactness, and dielectric properties 38 . We used the European Space Agency (ESA) Sentinel-1 data, a radar satellite constellation consisting of a C-Band synthetic aperture radar (SAR) sensor, operating at 5.405 GHz. The Sentinel-1 SAR image used here was acquired in a descending orbit with an interferometric wide swath mode (IW) at ground resolutions of 5 m × 20 m, and dual polarizations of VV + VH. Since Sentinal-1 is operated in the C-Band, it has an estimated penetration depth of 50 cm in very dry, sandy, loose soils 39 . We used ENVI v. 5.7 SARscape software for processing radar imagery. The used SAR processing sequences have generated geo-coded, orthorectified, terrain-corrected, noise free, radiometrically calibrated, and normalized Sentinel-1 images with a pixel size of 12.5 m. In SAR imagery subsurface fluvial deposits appear dark owing to specular reflection of the radar signals away from the receiving antenna, whereas buried coarse and compacted material, such as archeological remains appear bright due to diffuse reflection of radar signals 40 .

Other previous studies have shown that combining radar topographic imagery (e.g., Shuttle Radar Topography Mission-SRTM) with SAR images improves the extraction and delineation of mega paleo-drainage systems and lake basins concealed under present-day topographic signatures 3 , 4 , 22 , 41 . Topographic data represents a primary tool in investigating surface landforms and geomorphological change both spatially and temporally. This data is vital in mapping past river systems due to its ability to show subtle variations in landform morphology 37 . In low lying areas, such as the Nile floodplain, detailed elevation data can detect abandoned channels, fossilized natural levees, river meander scars and former islands, which are all crucial elements for reconstructing the ancient Nile hydrological network. In fact, the modern topography in many parts of the study area is still a good analog of the past landscape. In the present study, TanDEM-X (TDX) topographic data, from the German Aerospace Centre (DLR), has been utilized in ArcGIS Pro v. 3.1 software due to its fine spatial resolution of 0.4 arc-second ( ∼ 12 m). TDX is based on high frequency X-Band Synthetic Aperture Radar (SAR) (9.65 GHz) and has a relative vertical accuracy of 2 m for areas with a slope of ≤20% 42 . This data was found to be superior to other topographic DEMs (e.g., Shuttle Radar Topography Mission and ASTER Global Digital Elevation Map) in displaying fine topographic features even in the cultivated Nile floodplain, thus making it particularly well suited for this study. Similar archeological investigations using TDX elevation data in the flat terrains of the Seyhan River in Turkey and the Nile Delta 43 , 44 allowed for the detection of levees and other geomorphologic features in unprecedented spatial resolution. We used the Topographic Position Index (TPI) module of 45 with the TDX data by applying varying neighboring radiuses (20–100 m) to compute the difference between a cell elevation value and the average elevation of the neighborhood around that cell. TPI values of zero are either flat surfaces with minimal slope, or surfaces with a constant gradient. The TPI can be computed using the following expression 46 .

Where the scaleFactor is the outer radius in map units and Irad and Orad are the inner and outer radius of annulus in cells. Negative TPI values highlight abandoned riverbeds and meander scars, while positive TPI signify the riverbanks and natural levees bordering them.

The course of the Ahramat Branch was mapped from multiple data sources and used different approaches. For instance, some segments of the river course were derived automatically using the TPI approach, particularly in the cultivated floodplain, whereas others were mapped using radar roughness signatures specially in sandy desert areas. Moreover, a number of abandoned channel segments were digitized on screen from rectified historical maps (Egyptian Survey Department scale 1:50,000 collected on years 1910–1911) near the foothill of the Western Desert Plateau. These channel segments together with the former river course segments delineated from radar and topographic data were aggregated to generate the former Ahramat Branch. In addition to this and to ensure that none of the channel segments of the Ahramat Branch were left unmapped during the automated process, a systematic grid-based survey (through expert’s visual observation) was performed on the satellite data. Here, Landsat 8 and Sentinal-2 multispectral images, Sentinal-1 radar images and TDX topographic data were used as base layers, which were thoroughly examined, grid-square by grid-square (2*2 km per a square) at a full resolution, in order to identify small-scale fluvial landforms, anomalous agricultural field patterns and irregular ditches, and determine their spatial distributions. Here, ancient fluvial channels were identified using two key aspects: First, the sinuous geometry of natural and manmade features and, second the color tone variations in the satellite imagery. For example, clusters of contiguous pixels with darker tones and sinuous shapes may signify areas of a higher moisture content in optical imagery, and hence the possible existence of a buried riverbed. Stretching and edge detection were applied to enhance contrasts in satellite images brightness to enable the visualization of traces of buried river segments that would otherwise go unobserved. Lastly, all the pyramids and causeways in the study site, along with ancient harbors and valley temples, as indicators of preexisting river channels, were digitized from satellite data and available archeological resources and overlaid onto the delineated Ahramat Branch for geospatial analysis.

Geophysical survey and sediment coring

Geophysical measurements using Ground Penetrating Radar (GPR) and Electromagnetic Tomography (EMT) were utilized to map subsurface fluvial features and validate the satellite remote sensing findings. GPR is effective in detecting changes of dielectric constant properties of sediment layers, and its signal responses can be directly related to changes in relative porosity, material composition, and moisture content. Therefore, GPR can help in identifying transitional boundaries in subsurface layers. EMT, on the other hand, shows the variations and thickness of large-scale sedimentary deposits and is more useful in clay-rich soil than GPR. In summer 2022, a geophysical profile was measured using GPR and EMT units with a total length of approximately 1.2 km. The GPR survey was conducted with a central frequency antenna of 35 MHz and a trigger interval of 5 cm. The EMT survey was performed using the multi-frequency terrain conductivity (EM–34–3) measuring system with a spacing of 10–11 meters between stations. To validate the remote sensing and geophysical data, two sediment cores with depths of 20 m (Core A) and 13 m (Core B) were collected using a deep soil driller. These cores were collected from along the geophysical profile in the floodplain. Sieving and organic analysis were performed on the sediment samples at Tanta University sediment lab to extract information about grain size for soil texture and total organic carbon. In soil texture analysis medium to coarse sediment, such as sands, are typical for river channel sediments, loamy sand and sandy loam deposits can be interpreted as levees and crevasse splays, whereas fine texture deposits, such as silt loam, silty clay loam, and clay deposits, are representative of the more distal parts of the river floodplain 47 .

Data availability

Data for replicating the results of this study are available as supplementary files at: https://figshare.com/articles/journal_contribution/Pyramids_Elevations_and_Distances_xlsx/25216259 .

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Acknowledgements

This work was funded by NSF grant # 2114295 awarded to E.G., S.O. and T.R. and partially supported by Research Momentum Fund, UNCW, to E.G. TanDEM-X data was awarded to E.G. and R.E by the German Aerospace Centre (DLR) (contract # DEM_OTHER2886). Permissions for collecting soil coring and sampling were obtained from the Faculty of Science, Tanta University, Egypt by coauthors Dr. Amr Fhail and Dr. Mohamed Fathy. Bradley Graves at Macquarie University assisted with preparation of the sedimentological figures. Hamada Salama at NRIAG assisted with the GPR field data collection.

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Eman Ghoneim

School of Natural Sciences, Macquarie University, Macquarie, NSW, 2109, Australia

Timothy J. Ralph

Department of History, The University of Memphis, Memphis, TN, 38152-3450, USA

Suzanne Onstine

Near Eastern Languages and Civilizations, University of Chicago, Chicago, IL, 60637, USA

Raghda El-Behaedi

National Research Institute of Astronomy and Geophysics (NRIAG), Helwan, Cairo, 11421, Egypt

Gad El-Qady, Mahfooz Hafez, Magdy Atya, Mohamed Ebrahim & Ashraf Khozym

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Eman Ghoneim conceived the ideas, lead the research project, and conducted the data processing and interpretations. The manuscript was written and prepared by Eman Ghoneim. Timothy J. Ralph co-supervised the project, contributed to the geomorphological and sedimentological interpretations, edited the manuscript and the figures. Suzanne Onstine co-supervised the project, contributed to the archeological and historical interpretations, and edited the manuscript. Raghda El-Behaedi contributed to the remote sensing data processing and methodology and edited the manuscript. Gad El-Qady supervised the geophysical survey. Mahfooz Hafez, Magdy Atya, Mohamed Ebrahim, Ashraf Khozym designed, collected, and interpreted the GPR and EMT data. Amr S. Fahil and Mohamed S. Fathy supervised the soil coring, sediment analysis, drafted sedimentological figures and contributed to the interpretations. All authors reviewed the manuscript and participated in the fieldwork.

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Ghoneim, E., Ralph, T.J., Onstine, S. et al. The Egyptian pyramid chain was built along the now abandoned Ahramat Nile Branch. Commun Earth Environ 5 , 233 (2024). https://doi.org/10.1038/s43247-024-01379-7

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DOI : https://doi.org/10.1038/s43247-024-01379-7

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• Published: 15 May 2024

Factors and management techniques in odontogenic keratocysts: a systematic review

• Mario Dioguardi 1 ,
• Cristian Quarta 1 ,
• Diego Sovereto 1 ,
• Giorgia Apollonia Caloro 2 ,
• Andrea Ballini 1 ,
• Riccardo Aiuto 3 ,
• Angelo Martella 4 ,
• Lorenzo Lo Muzio 1 &
• Michele Di Cosola 1  

European Journal of Medical Research volume  29 , Article number:  287 ( 2024 ) Cite this article

119 Accesses

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Odontogenic keratocysts exhibit frequent recurrence, distinctive histopathological traits, a tendency towards aggressive clinical behavior, and a potential linkage to the nevoid basal cell carcinoma syndrome. The aim of this systematic review is to compile insights concerning the control of this condition and assess the effectiveness of various treatment approaches in reducing the likelihood of recurrence.

Materials and methods

The following systematic review adhered to the PRISMA guidelines. The systematic revision was registered on PROSPERO and  structured around the questions related to the population, intervention, control, outcome and study design (PICOS).

After conducting a search on the PubMed database, we initially identified 944 records. After using end-note software to remove duplicate entries, results totally with 462 distinct records. A thorough review of the titles and abstracts of these articles led to the selection of 50 papers for in-depth examination. Ultimately, following the application of our eligibility criteria, we incorporated 11 articles into our primary outcome analysis.

Among the studies examined, the most common location for these lesions was found to be in the area of the mandibular ramus and the posterior region of the mandible. In cases where the exact location wasn’t specified, the mandible emerged as the predominant site. When we considered the characteristics of these lesions in studies that mentioned locularity, most were described as unilocular in two studies, while in two other studies, the prevalence of multilocular lesions was observed. Risk factors associated with keratocyst recurrence include younger patient age, the presence of multilocular lesions, larger lesion size, and a longer anteroposterior dimension. Certain treatment methods have demonstrated a lack of relapses. These include the use of 5-fluorouracil, marsupialization, enucleation with peripheral ostectomy or resection, enucleation and curettage, as well as resection without creating continuity defects. However, it is important to note that further research is essential. Prospective studies and randomized trials are needed to collect more comprehensive evidence regarding the effectiveness of various treatment approaches and follow-up protocols for managing odontogenic keratocysts.

Clinical relevance

Odontogenic keratocysts still enter into differential diagnoses with other lesions that affect the jaw bones such as ameloblastama and other tumor forms, furthermore it is not free from recurrence, therefore the therapeutic approach to the lesion aimed at its elimination can influence both the possible recurrence and complications, knowledge of the surgical methods that offer the most predictable and clinically relevant result for the management of follow-up and recurrences.

Introduction

The odontogenic keratocyst (OKC) is a developmental cyst that originates from remnants of the dental lamina within the jawbones [ 1 ]. Several studies have reported a preference for males [ 1 , 2 , 3 ], with an incidence peak around the third decade [ 4 ] and a nearly equal distribution in other decades, with another small peak between 50 and 70 years of age [ 1 ]. It can occur in any area of the jawbones but is most commonly found in the mandible, with a particular preference for the mandibular angle extending to the mandibular ramus [ 4 ].

Diagnosis of OKC is typically  radiological. Radiographs commonly reveal well-defined radiolucent areas with  rounded or scalloped margins that are well demarcated; these areas can present as either multilocular or unilocular [ 5 ].

In the 2022 classification, OKC remains classified as a cyst; molecular studies have detected frequent mutations in the tumor suppressor gene PTCH1, a gene that activates the SHH pathway, leading to aberrant epithelial proliferation [ 1 ], sparking debates on whether OKC is a cyst or a cystic neoplasm. It was labeled as a keratocystic odontogenic tumor in 2005 [ 5 ], thus considered a cystic neoplasm, and later reclassified as a cyst in the 2017 classification [ 1 ].

Keratocysts are characterized by a high recurrence rate, specific histological features, aggressive clinical behavior, and can be associated with the nevoid basal cell carcinoma syndrome [ 6 ].

The mechanism of recurrence was proposed by Brannon [ 7 ] in 1976, suggesting it was due to three different mechanisms:

Incomplete removal of the cyst,

Growth of new keratocysts from satellite cysts,

Development of a new keratocyst in the area adjacent to the site of the primary keratocyst, interpreted as recurrence.

Odontogenic keratocysts can be treated with various surgical methods, which can be divided into conservative approaches and invasive approaches or a combination thereof [ 8 ]; in the literature, enucleation, marsupialization, resection, and the use of adjunct therapies such as Carnoy’s solution and cryotherapy are reported [ 1 , 4 , 9 ].

Despite many studies in the literature examining several therapeutic approaches in managing this lesion, it is still not clear which method provides lower recurrence rates without causing significant morbidity [ 10 ]; the purpose of this systematic review is to gather information on the management of this lesion and evaluate which treatment method results in fewer recurrences.

The following systematic review adhered to the PRISMA (Preferred Reporting Items for Systematic review and Meta-Analysis) protocol guidelines [ 11 ].

The systematic revision was registered on PROSPERO with number of: CRD42023480051.

The study was structured around the questions related to the population, intervention, control, outcome and study design (PICOS):

Population (P): individuals with non-syndromic or syndromic odontogenic keratocyst (initial cases) diagnosed histologically;

Intervention (I): surgical interventions for patients with odontogenic keratocystic, such as enucleation, enucleation coupled with curettage, enucleation with additional therapeutic measures (such as Carnoy's solution application, cryotherapy), marsupialization or decompression, with or without subsequent cystectomy and adjunctive therapy, and resection;

Control (C): not applicable;

Outcome (O): recurrence of KOT (Keratocystic Odontogenic Tumor) associated with distinct surgical treatments and characteristics of the keratocysts analyzed;

Study design (S): prospective randomized controlled clinical trials, controlled clinical investigations (either prospective or retrospective), and case series that explored and compared the diverse surgical approaches concerning recurrence over a suitable follow-up period (minimum of 1 year).

The formulation of the PICOS question can be summarized as follows: “What characteristics do the odontogenic keratocysts analyzed in the studies have? Which surgeries had the least recurrences during the follow-up?”.

Following the initial selection phase of records identified in various databases, potentially eligible articles were qualitatively assessed. This assessment aimed to investigate which surgical treatment was the most reliable in giving the least number of recurrences.

Eligibility criteria

This text discusses the process of selecting research articles for a study related to the recurrence of KOT associated with distinct surgical interventions, such as enucleation, with or without curettage and additional therapeutic measures, marsupialization or decompression, with or without subsequent cystectomy and adjunctive therapy, and resection.

The process involved initially identifying potentially eligible articles based on their abstracts. These articles were then subjected to a thorough examination of their full content to determine their suitability for both qualitative and quantitative analyses.

The criteria for including articles in the full-text analysis were studies relating to KOT treatments in which the number of recurrences and the general characteristics of the lesions are reported.

The exclusion criteria were applied to exclude the following types of studies:

Studies involving animals or conducted in a laboratory setting (in vitro)

Letters to the editor

Articles that did not adequately specify the type of surgical method used

Studies with an inadequate follow-up period (less than 1 year)

Clinical studies conducted more than 30 years ago (only studies from the last 30 years were included because classifications and surgical and therapeutic techniques have been constantly changing and improving, with generally earlier diagnoses and more suitable treatments with lower recurrence rates. Therefore, to avoid increasing the heterogeneity of the included studies and to prevent bias in the aggregated treatment results, the reviewers collectively decided to include only studies from 1989 onwards)

Review articles

Research methodology

Studies have been identified through bibliographic research on electronic databases.

The literature search was conducted on the search engines “PubMed”. The search on the providers was conducted between 02.09.2023 and 12.09.2023, and the last search for a partial update of the literature was conducted on 18.09.2023.

The following search terms were used on PubMed: “KOT” AND “Recurrence” (37 records), “odontogenic keratocyst marsupialization” (285 records), “odontogenic keratocyst enucleation” (622 records).

Screening methodology

The selection criteria and their combinations for searching were established prior to the record identification stage through mutual consensus between the two reviewers  (M.D. and M.D.C.) responsible for choosing potentially eligible articles. Following this, the records acquired were then assessed separately by the two independent reviewers, with a third reviewer  (A.B.) serving as an decision-maker in cases of uncertainty.

The screening process involved evaluating the titles and abstracts of articles, and in cases where there was uncertainty, a more in-depth examination of the article's content was conducted to remove records that were not relevant to the topics under review.

Following a search in the PubMed database, 944 records were initially located. Subsequently, after applying end-note software to eliminate duplications, 462 unique records remained. Upon reviewing the titles and abstracts of these articles, after this initial screening, a total of 50 articles were selected for a thorough examination of their full text by two reviewers. From these 50 articles, the ones that met the criteria for qualitative analysis for the outcome were identified. Finally, applying the eligibility criteria, we included 16 articles for the primary outcome analysis (Fig.  1 ).

Flowchart of the different phases of the systematic review

Study characteristics and data extraction

The included studies for the quantitative analysis were: Maurette et al. [ 12 ]; Nakamura et al. [ 13 ]; Bataineh and al Qudah [ 14 ]; Leung et al. [ 15 ]; Kolokythas et al. [ 9 ]; Berge et al. [ 16 ]; Pogrel and Jordan, [ 17 ]; Tabrizi et al. [ 18 ]; Zecha et al. [ 19 ]; Moellmann et al. [ 20 ]; Caminiti et al.[ 21 ], Stoelinga [ 4 ]; Dammer et al. [ 2 ]; Marker et.al. [ 22 ]; August et al.[ 23 ]; Brøndum and Jensen [ 24 ].

The extracted data included the journal (author, data, and reference); study design; number of patients (males/females); number of lesions; number of lesions associated with basal cell naevus syndrome (BCNS); mean age (range); site where the lesions were diagnosed; locularity (multilocular or unilocular); type of treatment; mean follow-up.

Finally, for each study, the number of relapses relating to each treatment was observed.

The data extracted are shown in Table  1 and 2 .

Risk of bias

The risk of bias was assessed using the Newcastle–Ottawa Scale (NOS) for cohort studies, assigning a value from 0 to 3 for each item, the assessment of the risk of bias was assessed by the first reviewer, and was deemed acceptable for all included studies, details are shown in Table  3

The articles included in this review analyze different types of keratocyst treatment and lesion characteristics.

Among the first to coin the term 'odontogenic keratocyst' was Philipsen in 1956, who, in a literature review, proposed the term 'odontogenic keratocyst' for all odontogenic cysts that exhibit epithelial keratinization [ 25 ].

The terminology, as adopted by Pindborg in 1962 and 1963 and also used by Toller in 1967, replaced the term ‘primordial cyst’ with ‘odontogenic keratocyst’, identifying 33 odontogenic keratocysts (study not included in this review) [ 26 , 27 , 28 , 29 ]

One of the early retrospective studies conducted on odontogenic keratocysts was performed by Pindborg, who retrospectively identified 26 keratinized cysts out of a total of 791 odontogenic cysts in 1962 [ 27 ].

The odontogenic keratocysts are often described in literature as benign cysts occurring within the bones, and they exhibit a propensity for infiltrative and aggressive growth patterns. These cysts make up an estimated 2–21.8% of all cysts affecting the jaw [ 24 , 25 ]. Moreover, there is a potential association between these cysts and genetic mutations, notably linked to nevoid basal cell carcinoma syndrome (NBCCS), a condition characterized by the presence of multiple OKCs in the jaw region [ 26 ]; this is also found in one of the articles included in this review [ 13 ], while in others the association was not specified [ 14 , 17 ] or there was no association at all [ 9 , 12 , 15 , 16 , 18 , 19 , 20 , 21 ]; many of these studies have placed the correlation with this syndrome in the exclusion criteria, as in the patients who are affected by it the probability that these cysts will reappear is high, and therefore it would be difficult to distinguish a recurrent event from the appearance of a new cyst [ 21 ]

These cysts are notorious for their tendency to grow aggressively in their immediate prossimity and for having a notably high rate of recurrence. Several contributing factors underpin this recurrence, including the use of inadequate treatment methods, incomplete elimination of the cyst, a high rate of cell division (mitotic index) within the cyst's epithelial cells, a larger cyst size, and the specific location of the cyst. The latter factor becomes especially problematic if it is challenging to access surgically [ 25 , 27 ]. Although they exhibit hostile conduct, OKC generally induce limited bone enlargement as they tend to proliferate within the intramedullary region, effectively growing within the bone [ 30 ].

Substantial lesions marked by substantial cortical plate erosion and engagement with neighboring structures may not produce symptoms in individuals, resulting in a delayed diagnosis [ 31 ].

The most frequent location of the lesions in the studies analyzed is at the level of the mandibular ramus and in the posterior mandible [ 12 , 13 , 14 , 15 , 16 , 19 ], and where the precise localization of the lesions is not specified, the mandible is the most frequent site [ 9 , 18 , 20 , 21 ]. In the studies in which locularity is specified among the characteristics of the lesions, the majority of the lesions were unilocular in two studies [ 13 , 21 ], while in two other studies the quantity of multilocular lesions was greater [ 14 , 15 ]. Younger patient age, multilocularity of the lesion, larger size, and longer anteroposterior dimension of the keratocyst have been identified as risk factors for keratocyst recurrence [ 15 ].

The treatments that have not had relapses are that with 5-fluorouracil [ 21 ], marsupialization [ 13 , 17 , 18 ], enucleation with peripheral ostectomy or resection [ 9 ], enucleation and curettage [ 12 ], and resection without continuity defects [ 14 ].

Decompression has been studied in 5 articles [ 9 , 12 , 22 , 23 , 24 ]; this method has the advantage of having minimal surgical morbidity and reduced risk to anatomical structures associated with the lesion, such as developing nerves or teeth [ 22 ]. Decompression and marsupialization techniques involve creating a communication between the cyst and the oral cavity, relieving pressure and allowing cyst shrinkage and bone apposition [ 12 ]. Clinical and radiographic resolution of OKCs after marsupialization is relatively rapid, typically within 19 months [ 17 ]. In studies where marsupialization alone was used for treatment, there were no relapses in two studies [ 17 , 18 ], while Zecha et al. [ 19 ] found four cases of relapse in ten patients treated with marsupialization.

Decompression and marsupialization are non-invasive treatment options for keratocysts, but require patient cooperation, including regular irrigation and follow-up [ 17 , 18 ].

Topical 5-fluorouracil is known for its antiproliferative effects on keratocystic epithelium and satellite cysts; furthermore, its use has some advantages, such as technical ease and the lack of neurotoxicity [ 21 ] and, in the only study of this review in which it were used in the treatment, there were no relapses [ 21 ].

Other treatment modalities used to reduce keratocyst recurrence are resection of the affected maxillary segment and enucleation with additional treatments such as curettage or ostectomy [ 9 , 14 ], which in these studies have not given recurrences, which, as regards resection, is a similar result to other studies in the literature [ 4 , 8 , 32 ]. However, despite the remarkably high success rate of this approach, resection is not widely embraced as a standard procedure, primarily due to concerns regarding its aggressiveness and associated postoperative complications, including morbidity [ 33 ]. Enucleation, often combined with curettage (the process of scraping the walls of the lesion cavity) or ostectomy (the surgical removal of bone tissue), is commonly used to treat keratocysts; although a more conservative treatment than resection, the effectiveness of this modality may be limited in cases where vital structures, such as the exposed inferior alveolar nerve, are at risk or when there is a perforation of the bony wall exposing the overlying mucosal tissue [ 15 ].

Carnoy’s solution was used in three studies [ 15 , 20 , 21 ] and of these studies one used the modified Carnoy’s solution [ 21 ]. The FDA avoid the use of Carnoy's solution containing chloroform in the United States, leading to the adoption of a modified formula. However, the modified formula has been found to have a higher relapse rate, suggesting the potential role that traditional Carnoy’s solution may have in treatment [ 34 ].

There are risk factors associated with the recurrence of odontogenic keratocyst, such as age, multilocularity, lesion size and radiographic characteristics.

The various surgical techniques used to treat keratocysts have potential benefits, including preservation of jaw function, reduction of the potential for recurrence, and eradication of the cystic lesion.

Marsupialization or decompression are advantageous conservative treatment options that aim to minimize surgical invasiveness while effectively managing keratocysts.

Long-term follow-up and monitoring of patients treated for these lesions is important to detect recurrence early.

There is a need for further research, prospective studies and randomized trials to gather more evidence on the effectiveness of different treatment methods and follow-up protocols for odontogenic keratocysts.

Availability of data and materials

All data generated or analyzed during this study are included in this published article.

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Mario Dioguardi, Cristian Quarta, Diego Sovereto, Andrea Ballini, Lorenzo Lo Muzio & Michele Di Cosola

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Conceptualization, M.D.and C.Q.; methodology, M.D.; software, M.D. and D.S.; validation, M.D. and A.B.; formal analysis, M.D.; investigation, M.D. and C.Q.; data curation, M.D. and D.S.; bibliographic reserach, C.Q. and R.A.; writing—original draft preparation, M.D. and C.Q.; writing—review and editing, M.D. and A.B.; visualization, D.S and M.D..; supervision L.L.M.., and M.D.C.; Critical revision of the manuscript for important intellectual content M.D., C.Q.; and A.B.; Bioinformatic analysis review, A.M.; project administration, L.L.M. All authors have read and agreed to the published version of the manuscript.

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Dioguardi, M., Quarta, C., Sovereto, D. et al. Factors and management techniques in odontogenic keratocysts: a systematic review. Eur J Med Res 29 , 287 (2024). https://doi.org/10.1186/s40001-024-01854-z

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3 to 5 years

In November 2023, a buzzy solar technology broke yet another world record for efficiency. The previous record had existed for only about five months—and it likely won’t be long before it too is obsolete. This astonishing acceleration in efficiency gains comes from a special breed of next-­generation solar technology: perovskite tandem solar cells. These cells layer the traditional silicon with materials that share a unique crystal structure.

In the decade that scientists have been toying with perovskite solar technology , it has continued to best its own efficiency records, which measure how much of the sunlight that hits the cell is converted into electricity. Perovskites absorb different wavelengths of light from those absorbed by silicon cells, which account for 95% of the solar market today. When silicon and perovskites work together in tandem solar cells, they can utilize more of the solar spectrum, producing more electricity per cell. 

Technical efficiency levels for silicon-­based cells top out below 30%, while perovskite-only cells have reached experimental efficiencies of around 26%. But perovskite tandem cells have already exceeded 33% efficiency in the lab. That is the technology’s tantalizing promise: if deployed on a significant scale, perovskite tandem cells could produce more electricity than the legacy solar cells at a lower cost. 

But perovskites have stumbled when it comes to actual deployment. Silicon solar cells can last for decades. Few perovskite tandem panels have even been tested outside. 

The electrochemical makeup of perovskites means they’re sensitive to sucking up water and degrading in heat, though researchers have been working to create better barriers around panels and shifting to more stable perovskite compounds. 

In May, UK-based Oxford PV said it had reached an efficiency of 28.6% for a commercial-size perovskite tandem cell, which is significantly larger than those used to test the materials in the lab, and it plans to deliver its first panels and ramp up manufacturing in 2024. Other companies could unveil products later this decade. 

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