Objective : The purpose of this study was to evaluate mandibular impacted third molars three-dimensionally using multidetector-row computed tomography (MDCT) and to clarify the relationship of age and sex with root characteristics.

Materials and Methods : The participants consisted of 706 patients who underwent MDCT and had mandibular impacted third molars (295 males, 411 females, age 20-79 years). The evaluations included root curvature, root ankylosis, and root hypercementosis, and their associations with age and sex were examined. Statistical analyses were performed using the Mann-Whitney U test to compare median ages based on the presence of root characteristics, and the chi-square test for differences between sexes. A P-value of＜0.05 was considered statistically significant.

Results : No significant sex differences were observed in root ankylosis (chi-square test, p＝0.47). However, the mean age was significantly higher in the group with ankylosis (Mann-Whitney U test, p＜0.05), and also in the group with root hypercementosis (Mann-Whitney U test, p＜0.05). Additionally, there was a higher proportion of females in the group with root hypercementosis (chi-square test, p＜0.05).

Conclusion : This study revealed that the root characteristics of mandibular impacted third molars are related to age and sex.

 In this study, ultra-high-resolution micro-computed tomography (micro-CT) was used to classify the root canal morphology of mandibular central incisors and investigate the incidence of accessory root canals as well as to identify some aspects of their association with root canal re-infection during and after incisor-infected root canal treatment. The specimens used were 100 mandibular central incisors from Japanese individuals held in the collection of the Department of Anatomy of Tokyo Dental College. They were scanned by micro-CT, after which three-dimensional reconstruction was conducted, the pulp cavity and accessory root canals were observed, the root canal morphology was classified, and the incidences of the different types of accessory root canals were calculated. The root of the mandibular central incisor was a single root in all teeth from Japanese individuals. The main root canal was classified as Type Ⅰ in 87.0％ of cases, as Type Ⅲ in 10.0％ of cases, and the incidence of lateral branches was 36.0％.

 These results suggest that, despite the simplicity of the root canal, the existence of accessory root canals should be borne in mind during root canal treatment.

 The purpose of this study was to assess the classification of root canal morphology and the frequency of occurrence of accessory root canals in Japanese maxillary central incisors using micro-CT with ultra-high-resolution imaging, and to elucidate some aspects of their relationship to root canal re-infection during and after root canal treatment in maxillary central incisors. Fifty Japanese maxillary central incisors from the Department of Anatomy, Tokyo Dental College were used as samples. After micro-CT imaging, three-dimensional construction was performed to assess the morphology of the pulp cavity and the incidence of secondary root canals. All maxillary central incisors in Japanese patients had a single root. All main root canals of the maxillary central incisor were classified as Type I (100.0％). The incidence of accessory root canals was 66.0％, and most were found from the center of the root to the apical one-third. The most common cross-sectional shape of root canals was circular. The results suggest that, in root canal treatment of maxillary central incisors in Japanese patients, although the root canals are simple, the presence of accessory root canals should be carefully considered for endodontic treatment.

 The purpose of this study was to investigate the three-dimensional structural characteristics of the frontal sinus in neonatal, pediatric, and adult skulls using multi-slice CT imaging data, and to determine whether right or left frontal sinuses were present at each stage. The volume of the skulls was also measured. The subjects were Indian dry skulls from the Department of Anatomy, Tokyo Dental College. Three groups were selected according to tooth eruption status : neonate, deciduous (Hellman’s dental age stage ⅡA), and permanent (Hellman’s dental age stage ⅣA). After multi-slice CT imaging, three-dimensional reconstruction was performed, and the mean and SD in each group were calculated by volumetric measurement of each of the left and right side of the frontal sinuses. In the neonate and infant periods, some frontal sinuses were absent on either or both sides. In the permanent dentition, frontal sinuses were present bilaterally, but the left frontal sinus was larger than the right frontal sinus in all cases.

 The purpose of this study was to acquire 3D shapes of the left and right auricles of the same individual using a 3D scanner, perform mirroring and superimpose the STL data, and quantitatively evaluate whether the symmetry of the auricles is sufficient for use in personal identification. Even in the case of personal identification where ipsilateral auricular data cannot be obtained, the contralateral auricle can be used if the identicalness of the left and right auricles is ensured. We scanned the temporal regions including the left and right auricles of 23 cadavers in the collection of the Department of Anatomy, Tokyo Dental College, using a 3D scanner, and obtained STL data. After mirroring the STL data of the left auricle, the STL data of the left and right auricles were superimposed, and the differences were calculated. By superimposing the STL data of this study it was possible to compare the shape of the auricles without being affected by factors related to the imaging angle. The results showed that the external shapes of the left and right auricles were highly identical. This result suggests that identification performance is not affected by the use of either the left or right auricle when mirroring is effectively utilized for personal identification using the auricle.

 The purpose of this study was to clarify the influence of the mutual growth and development of the maxillary sinus and infraorbital canal on the formation of the maxillofacial region according to the volume of the maxillary sinus and infraorbital canal during the neonatal period, deciduous period, and permanent dentition, and their volume ratio to the nasal cavity. The samples were dried Indian skulls from the Department of Anatomy, Tokyo Dental College. Three groups were selected according to tooth eruption status : neonate, deciduous (Hellman’s dental age stage ⅡA), and permanent (Hellman’s dental age stage ⅣA). After multi-slice CT imaging, three-dimensional reconstruction was performed, and the mean and SD in each group were calculated by volumetric measurement of each of the maxillary sinus and infraorbital canal. In the early stages of growth and development immediately after birth, both the maxillary sinus and infraorbital canal begin to grow gradually. However, with the eruption of teeth, the volume of the maxillary sinus in particular increases markedly, expanding throughout the maxillary body as if pushing the infraorbital canal into the infraorbital wall. These findings collectively suggest that the growth of the maxillary sinus plays a significant role in maxillofacial development.

Purpose : This study aimed to determine the relationship between mandibular submarginal cortical bone morphology and vertical maxillofacial morphology in patients with skeletal mandibular prognathism using the mandibular cortical index (MCI) and digital imaging.

Materials and methods : The subjects consisted of 142 patients diagnosed with skeletal mandibular prognathism. FMA of the lateral cephalogram analysis was used to classify the patients into long, middle, and short face type. MCI Ⅰ was classified as Group 1, and MCI types Ⅱ and Ⅲ were classified as Group 2 using digital panoramic radiographs.

Results : Group 2 with low bone mineral density accounted for 75.0％ of the long face, 56.1％ of the medium face, and 44.8％ of the short face type, showing a significant difference between the long and short face types.

Conclusion : These results suggest that the long face type has low mandibular bone density.

 Root canal treatment of the maxillary first molar is often described as difficult. The presence of two root canals in the distal root is very rare, occurring in only 1.7％ of cases, and the existence of multiple disto-buccal root canals is hard to identify on dental X-rays, and their treatment is also difficult. In the present study, we performed a Cone-beam computed tomography (CBCT) examination to identify the cause of persistent discomfort after pulpectomy. On examination, we found the disto-buccal second root canal in addition to the mesio-buccal second root canal using a surgical microscope, and root canal treatment was performed. As a result, good clinical success was achieved.

 From this result, it is concluded that the use of CBCT and surgical microscope for root canal treatment in case of a maxillary first molar with five root canals is valuable.