Dental systematic reviews and their shortcomings based on umbrella reviews

Evidence-based dentistry has progressed from case reports and series to best evidence consensus statements; to non-randomized and randomized controlled studies; to systematic reviews (SRs), which analyze individual studies; and to umbrella reviews (URs), which now evaluate SRs. The purpose of this article is to review and summarize the findings of recent dental URs selected by the authors because they analyzed the quality of SRs, identified their strengths and weaknesses, and represented multiple disciplines of dentistry and diverse journals.

A PubMed search was completed using the keywords "umbrella review, dentistry" and the filters "meta-analysis" and "systematic review" along with the years 2022-2024. There were 93 URs listed, with 56 being dental-related. The 56 URs were reviewed, and 15 were collectively selected by the authors to be summarized as examples of multiple dental disciplines and dental-related treatments published in a diverse group of dental journals.

The 15 selected URs exhibited similar formats with findings based on the included SRs. The results of the 15 URs are summarized and presented along with the strengths and weaknesses noted in the SRs.

The URs included in this article assessed the quality of SRs based on AMSTAR 2 (AMSTAR 2 is a critical appraisal tool used to assess the methodological quality of systematic reviews, particularly those focusing on healthcare interventions), ROBIS (ROBIS is the first rigorously developed tool designed specifically to assess the risk of bias in systematic reviews), and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Deficiencies were reported relative to the following items: failure to register the protocol before starting the review; incomplete literature search; absence of a list of excluded studies and lack of justification for the exclusions; inadequate review methods; lack of reporting the sources of funding; failing to assess risk of bias (ROB) or an unsatisfactory technique to assess ROB; not listing potential sources of conflict of interest; and lack of homogeneity in the study design, which prevented performing a meta-analysis. These findings indicate the need for careful study of SR and UR guidelines related to design and review, assessment of bias risk, and review reporting before applying the conclusion to clinical practice. Clinicians need to be aware of the deficiencies present in SRs and URs. Also, it is important to recognize that reviews are based on only those studies that met the inclusion criteria of the authors, and the exclusion of studies is fraught with potential bias.