Applicability of tooth cementum thickness as an age marker: systematic review and meta-analysis

The age estimation by tooth cementum thickness is a method that has been discussed regarding its applicability. The aim of this study was to conduct a systematic review on the use of tooth cementum thickness as a biomarker for age estimation in adults, as well as a meta-analysis to assess the method's reliability. The search was conducted on Embase, LILACS, PubMed/MEDLINE, SciELO, Scopus, and Web of Science databases. Two independent reviewers used inclusion and exclusion criteria to select and assess relevant studies. For bias risk assessment, a checklist proposed by the Joanna Briggs Institute was applied. Pearson and Spearman correlation coefficients were considered as effect measures for the meta-analysis between tooth cementum thickness and chronological age. Heterogeneity among studies was evaluated using Cochran's $Q$ test ( $p<0.05$ ), I² index, and Graphic Display of Heterogeneity plot. Meta-analysis robustness was assessed using Baujat plots, and publication bias was checked using DOI plots and the Luis Furuya-Kanamori index. Most selected studies showed low risk of bias. Although not all studies were included in the meta-analysis, moderate heterogeneity was found among those included. The synthesized result indicated that tooth cementum thickness has a moderate correlation with chronological age, both when the outlier study is included ( $r=0.59[0.48;0.69]$ ) and when the outlier is removed ( $r=0.57[0.45;0.68]$ ). It is concluded that tooth cementum thickness represents a potential age biomarker that can be useful in age estimation methods for adults. However, the presented results should be considered cautiously, emphasizing the need for further primary studies.