Geographic patterns of the number of root canals in permanent molars. A Systematic Review

IntroductionThe variability in the distribution and number of root canals in human permanent molars makes endodontic therapy difficult if the prevalence of these patterns is not well known. ObjectiveTo synthesize scientific evidence on geographical variations in the number of root canals in permanent molars. MethodsA study conducted at the University of Medical Sciences of Havana analyzed the number of root canals in permanent molars. We searched for primary studies published in English, Spanish, or Portuguese that reported the number of canals in each tooth. We excluded clinical case studies, editorials, and studies that did not provide specific information on duct anatomy. A sensitivity analysis was performed to assess the impact of the methodological quality of the studies in the two groups. The findings were synthesized by grouping the studies by geographical region and describing the prevalence of different root canal configurations. ResultsData on permanent molars were collected from 93 studies that contributed 60402 molars studied. In Africa, the first and second upper molars commonly have three root canals (45.62% and 41.31%, respectively), similar to the first and second lower molars (59.79% and 67.55%, respectively). In America, the upper first molar most frequently has four root canals (56.66%). In Asia, it is more common to find that all molar groups have three canals (51.09%- 65.58%), except for the lower thirds, which may have two or three canals (42.88% and 57.12%). In Europe, all molars are frequently present with three canals, except for the lower third. In Oceania, the first upper molars commonly have six root canals (65%). ConclusionSignificant variations in the number of root canals in permanent molars according to geographic region were observed. Distinct patterns were observed in the Americas, Asia, Africa, Europe, and Oceania, with varying prevalences of different root canal configurations.