Prevalence of 3-rooted first permanent molars among a Shanghai Chinese population

ObjectivesThis study aimed to assess the prevalence of 3-rooted mandibular first molars among a Shanghai Chinese population by using periapical radiographs.MethodsA total of 510 patients possessing both mandibular first molars were selected. The radiographs of these cases were evaluated under optimal conditions using double magnifying glasses. The incidence of 3-rooted mandibular first molars and the correlation between occurrences in males and females and between the left and right sides were recorded and analyzed. A total of 1020 mandibular first molars were evaluated.ResultsA total of 165 patients were found to have a 3-rooted mandibular first molar: 92 males and 73 females (P = .106). The overall incidence of patients with 3-rooted mandibular first molars was 32.35%. Of all the patients with 3-rooted molars, 67.27% (111/165) of cases occurred bilaterally. The incidence of teeth showing an extra root was 27.06%. The occurrence of such permanent 3-rooted mandibular first molars also did not differ significantly between the right side (n = 142, 13.92%) and the left side (n = 134, 13.14%; P = .573).ConclusionsThe prevalence and bilateral incidence of 3-rooted mandibular first molars among the Shanghai Chinese population was high and such variation varied among Chinese populations living in different areas.