3根を有する上顎第一小臼歯の一例

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In this study, we examined an upper first premolar with three roots of very low prevalence. In addition, we examined the pulp cavity of this tooth three dimensionally without damageing the tooth using micro focus computed tomography (following Micro- CT). A left upper first premolar was obtained from a male (aged 12 yrs 7 mths) as a convenience extraction for orthodontic purposes. The subject's medical history was unremarkable. In the subject's family history, the mother also had a convenience extraction of upper and lower first premolar for orthodontic purposes when she was 16 yrs and 6 mths of age. The details of the extracted tooth were measured using vernier calipers (1/20 mm), and compared with the Japanese mean. Cystography by Micro-CT (SMX-225CT, Shimadzu Co.) was performed in the mesio-distal direction with a canal voltage of 85KV and a canal current of 300 uA. A two dimensional slice image of 20 um thickness was obtained, and transformed into a three dimensional reconstruction image of the contours and cavity of the tooth using the volume rendering method. Our results indicate that the left upper first premolar examined in this study was larger than the Japanese mean previously reported. Although no difference was observed between average Japanese tooth form and our observation of the fundamental configuration of the anatomical tooth crown, a longitudinal sulcus on the root trunk of the buccal side had acervical enamel projection on its surface. During the development of the teeth, the root trunk is formed at the end of the enamel formation, and the configuration of the tooth root is already determined by the cervical enamel projection. Our observations do not address whether the existence of the longitudinal sulcus promotes the formation of the enamel projection or vice versa. We confirmed by Micro-CT that this premolar had three root canals, with two horns of the pulp chamber on the buccal and lingual side. Therefore, while the horns of the pulp chamber resembled an upper premolar, the floor of the pulp chamber resembled an upper molar. Our results suggest that the cervical enamel projection onto the root trunk of the buccal side may induce a bifurcation of the buccal root in a mesio-distal direction.
岩手医科大学歯学会の論文
2002-08-19

3根を有する上顎第一小臼歯の一例

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