title: Incidence of three-rooted mandibular first molars among contemporary Japanese individuals determined using multidetector computed tomography.
abstract: OBJECTIVE
  The purpose of this study was to determine the incidence of three-rooted mandibular first molars in a contemporary Japanese population using multidetector computed tomography (MDCT) and examine whether this characteristic root form may be useful for identification purposes.
  
  
  METHODS
  Prior to their forensic autopsies, we obtained MDCT scans of 365 cadavers (255 males, 110 females) with mandibular first molars on both sides. Altogether, 730 mandibular first molars were examined morphologically on reconstructed CT images, and the incidence of three-rooted molars was recorded. The results were analyzed statistically to determine sex and left-right differences using the chi-square test.
  
  
  RESULTS
  In all, 189 (25.9%) of the 730 mandibular first molars had three roots: 79 (31.0%) in the 255 males and 35 (31.8%) in the 110 females. No statistically significant difference was found between the sexes. In the 39 individuals who had unilateral three-rooted mandibular first molars, 7 (17.9%) were on the left side and 32 (82.1%) were on the right side, indicating a statistically significant predominance on the right side.
  
  
  CONCLUSIONS
  The incidence of three-rooted mandibular first molars in contemporary Japanese individuals was 25.9%, with no statistically significant sex difference, but in the case of unilateral three-rooted teeth, with a statistically significant predominance on the right side. Our study found that Japanese and northeastern Asians have a high incidence of the three-rooted mandibular first molars among individuals of Mongolian origin; this finding may be a useful screening tool for identification of unknown individuals.
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan. Electronic address: acua2807@chiba-u.jp.
authors: Namiko
authors: N
authors: Ishii
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan.
authors: Ayaka
authors: A
authors: Sakuma
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan; Department of Forensic Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Yohsuke
authors: Y
authors: Makino
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan; Department of Forensic Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Suguru
authors: S
authors: Torimitsu
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan.
authors: Daisuke
authors: D
authors: Yajima
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan.
authors: Go
authors: G
authors: Inokuchi
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan.
authors: Ayumi
authors: A
authors: Motomura
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan; Department of Forensic Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Fumiko
authors: F
authors: Chiba
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan.
authors: Yumi
authors: Y
authors: Hoshioka
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan; Department of Forensic Medicine, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Hirotaro
authors: H
authors: Iwase
authors: Department of Legal Medicine, Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba City, Chiba Prefecture 260-8670, Japan.
authors: Hisako
authors: H
authors: Saitoh
mesh_terms: D000328:Adult; D044466:Asian People; D001344:Autopsy; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan; D008297:Male; D008875:Middle Aged; D008963:Molar / Q000033:anatomy & histology*; D061330:Multidetector Computed Tomography; D011859:Radiography; D014092:Tooth Root / Q000033:anatomy & histology* / Q000000981:diagnostic imaging
keywords: Contemporary Japanese individuals; Forensic anthropology; Forensic odontology; Postmortem computed tomography; Three-rooted mandibular first molars