2 A number of studies have reported that the number of roots and root canal types may vary according to ethnicity, and a literature JQ1 1268524-70-4 search reveals that comparatively few studies have evaluated the root anatomy of mandibular premolars and molars in ethnic populations using cone-beam computed tomography (CBCT).3 CBCT is advancement in CT imaging, and it has potential applications for the imaging of high-contrast structures in the head and neck, as well as dentomaxillofacial regions; it has been applied in periodontal evaluations; endodontics, including assessment of periapical pathology and periradicular surgical planning; orthodontic evaluations; and dentoalveolar trauma evaluation.

4,5 The CBCT scanner can collect volume data by means of a single rotation with a cone-shaped x-ray beam and two-dimensional detectors,6 and CBCT is capable of providing images of high diagnostic quality, with shorter scanning times and lower radiation dosages compared to those of conventional CT scans.7,8 Recently, a study was conducted to investigate the incidence of distolingual (DL) roots in the mandibular molars using CBCT scans, and it was suggested that this method may be a practical tool for noninvasive and 3-dimensional reconstruction imaging for use in morphologic analyses and endodontic applications.9 The main purpose of this study was to investigate the root and morphology of Korean mandibular premolars and molars, and to evaluate the prevalence of three-rooted mandibular first molars having distolingual root (radix entomolaris), three-rooted mandibular second molars, and C-shaped (gutter-shaped) roots in mandibular second molars.

MATERIALS AND METHODS CBCT images of mandibular first premolars, second premolars, first permanent molars, and second premolars were collected from patients who visited the Dental Hospital at Seoul St. Mary��s Hospital, Seoul, Korea, between March 2008 and June 2011. We evaluated 430 patients aged 38.1��18.1 (n=236 females and 194 males; Table 1). This study was approved by the Institutional Review Board. Table 1 Descriptive statistics of study population according to the age and gender. The axial thickness was 0.4 mm, the voxels were isotopic, and the obtained data were analyzed with M-view? (Seoul, Korea). Serial axial CBCT images were evaluated continuously by moving the toolbar from the floor of the pulp chamber to the apex to determine the number of roots and their morphology.

To evaluate the bilateral occurrence of 3-rooted mandibular first molars, 3-rooted mandibular second molars, and C-shaped mandibular second molars, we only evaluated patients who had bilateral mandibular first molars or bilateral mandibular second molars (Figure 1�C6). Figure 1 Mandibular first molars with two roots occurring bilaterally. Figure 6 Mandibular Cilengitide second molars with three roots.