Evaluation of root and canal systems of mandibular first molars in Taiwanese individuals using cone-beam computed tomography.

BACKGROUND/PURPOSE: Cone-beam computed tomography (CBCT) can provide valuable data for root canal systems of human teeth. This study used CBCT to evaluate the number of roots and canals in mandibular first molars in Taiwanese individuals. METHODS: We screened 151 patients (76 male and 75 female) scheduled for CBCT scan prior to implantation, or orthodontic, endodontic, or periodontic treatment between June 2006 and March 2009 at the Department of Dentistry, Cardinal Tien Hospital, Taipei, Taiwan. A total of 237 image samples of mandibular first molars were obtained and analyzed for their number of roots and canals. RESULTS: We found that 177 (74.7%) mandibular first molars had two roots and 60 (25.3%) had three roots. Of the 237 teeth, 133 (56.1%) had three canals, 96 (40.5%) had four, and eight (3.4%) had two canals. Of the 86 patients (43 male and 43 female) with bilateral mandibular first molars, 22 (25.6%, 15 male and 7 female) had bilateral three-rooted mandibular first molars, and six (7.0%, 4 male and 2 female) had unilateral three-rooted mandibular first molars. The chi(2) test showed a significantly higher incidence of three-rooted mandibular first molars in male (44.2%, 19/43) than in female (20.9%, 9/43, p = 0.038) subjects. CONCLUSION: Our results showed a high overall incidence (32.6%) of three-rooted mandibular first molars in Taiwanese individuals. CBCT could be a valuable tool for identifying an extra distolingual root in mandibular first molars.

Analysis of the width of vertical root fracture in endodontically treated teeth by 2 micro-computed tomography systems.

INTRODUCTION: Early detection of vertical root fracture (VRF) is important for clinical endodontic practice. The purpose of this study was to measure the fracture width (distance between 2 sides of the fracture) of VRF teeth in vitro by using 2 micro-computed tomography (µ-CT) systems with different spatial resolution and voxel size. METHODS: Thirty-seven endodontically treated teeth with VRF were scanned by 80-µm pixel size µ-CT. Fifteen teeth with no obvious fracture line, blurred image, or fracture space less than 100 µm were scanned by 9-µm pixel size µ-CT. RESULTS: Presence of 2 VRF lines was more common in premolars (82%) than in molars (53%). In 7 premolars (32%) and 9 molars (60%), the VRF lines extended to within the apical 3 mm of the root. All fracture lines were detected by 9-µm pixel size µ-CT, but only 22 of 37 VRF teeth had vertical fracture identified by 80-µm µ-CT. From µ-CT examination, none of the fracture lines showed consistent and uniform fracture space. If 2 fracture lines were present, they were typically in opposite (not linear) directions. There was a significant correlation between 2 fracture lines or fracture lines extending within the 3 mm of the apex and fracture width greater than 100 µm. CONCLUSIONS: Application of 9-µm µ-CT can be accurately used for early detection of VRF. Fracture characteristics (eg, number of fracture lines, extension of fracture line) may affect the fracture width. Appropriate use of µ-CT technology can be helpful for early diagnosis of VRF.