Prevalence of Distolingual Roots in the Permanent Mandibular Molars in a Chinese Population

Objective: The purpose of this study was to detect the prevalence of distolingual(DL) roots in the permanent mandibular molars in a Chinese population by using cone-beam computed tomography(CBCT).Methods : A total of 500Chinese patients'CBCT images were examined.The incidences and bilateral concurrence rates of DL roots were determined for the permanent mandibular first,second and third molars.The differences between sexes and sides were tested by using Chi-square tests.The antimeric correlations for occurrence of the trait were analyzed with the Spearman's rank order correlation test.Results : The prevalence of 3-rooted mandibular first molars was 31.98%(134 / 419individuals) calculated by individuals,and 25.89%(217 / 838teeth) calculated by teeth.The bilateral concurrence rate was 61.94%.A significant right-side predilection was found in the female group(P=0.025) as well as for both sexes combined(P=0.009).The Spearman's correlations coefficient between antimeres was 0.77(P=0.000).The prevalence of DL roots in the mandibular second and third molars were 2.02%(8 / 396individuals) and 12.10%(19 / 157individuals),respectively.The corresponding bilateral concurrence rate was 12.50% and 35.83%,and the bilateral correlation coefficient was 0.22(P=0.000) and 0.50(P=0.000),respectively.Conclusion : Clinicians should be aware of the high prevalence of the DL roots in the Chinese population.Understanding the pattern of occurrence would be useful for dental treatment.

[-Abstract] Objective： The purpose of this study was to detect the prevalence of distolingual （DL） roots in the per- manent mandibular molars in a Chinese population by using cone-beam computed tomography （CBCT）. Methods： A total of 500 Chinese patients＇ CBCT images were examined. The incidences and bilateral concurrence rates of DL roots were determined for the permanent mandibular first, second and third molars. The differences between sexes and sides were tested by using Chi-square tests. The antimeric correlations for occurrence of the trait were ana- lyzed with the Spearman＇s rank order correlation test. Results： The prevalence of 3-rooted mandibular first molars was 31.98% （134/419 individuals） calculated by individuals, and 25.89% （217/838 teeth） calculated by teeth. The bilateral concurrence rate was 61.94 %. A significant right-side predilection was found in the female group （P= 0. 025） as well as for both sexes combined （P= 0. 009）. The Spearman＇s correlations coefficient between antimeres was 0.77 （P=0. 000）. The prevalence of DL roots in the mandibular second alad third molars were 2.02% （8/396 individuals） and 12.10% （19/157 individuals）, respectively. The corresponding bilateral concurrence rate was 12. 50% and 35.83%, and the bilateral correlation coefficient was 0.22 （P=0. 000） and 0.50 （P=0. 000）, respective- ly. Conclusion.. Clinicians should be aware of the high prevalence of the DL roots in the Chinese population. Under- standing the pattern of occurrence would be useful for dental treatment.