The prevalence of three-rooted permanent mandibular molars in a Slovenian population: A radiographic study

Background: Three-rooted permanent mandibular molars (PMMs) have great clinical significance and interesting geographical distribution. Aim: The aim of this retrospective study was to assess their prevalence among a Slovenian dental school patient population. Materials and methods: A total of 3668 PMMs (1361 first, 1573 second, and 734 third) were evaluated by means of intraoral (periapical and bite-wing) radiographs that were collected from dental records of 1317 patients (708 females and 609 males) aged 13-92 years (mean age 37.3 years). The radiographs were evaluated independently by two observers under optimal conditions using a viewing box and a magnifying glass. 95% confidence intervals (CI) for the prevalence of three-rooted PMMs in the population were estimated using Wald's method. The Fisher's exact test was applied to examine any statistically significant difference among PMM groups, between left and right teeth and between male and female patients. Results: Three roots were identified in 1.32% [0.82%-2.10%, 95% CI] of the evaluated first PMMs, 0.25% [0.07%-0.61%, 95% CI] of second, and 1.77% [1.01%-3.04%, 95% CI] of third PMMs. The overall prevalence of three-rooted PMMs was 0.95% [0.68%-1.33%, 95% CI]. The second PMM was less often affected than the first or the third PMM (p < 0.001). No statistically significant differences for three-rooted first, second and third PMMs were detected with respect to sex (p > 0.05) or the side of occurrence (left vs. right side, p > 0.05). Conclusions: A relatively low prevalence of three-rooted PMMs in the examined Slovenian population is in agreement with the available data for Europeans. Three-rooted variants occur least frequently in second PMMs. From a clinical viewpoint, the possibility of three-rooted PMMs should always be considered and looked for, even when treating indigenous European patients.