ヒトの下顎小臼歯における形態ならびに隣接歯間との関連性について
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概要
- 論文の詳細を見る
Studies of the morphology of the mandibular premolars reveal interesting matters from the viewpoint of phylogenesis. The morphology of the mandibular premolars therefore was investigated and their morphological relation with the proximate teeth, or the mandibular canines and first molars were examined. The results were as follows : 1. In the morphology of the crown of the mandibular first molars, growth of the lingual cusp was poor. Consequently, cusps were mostly types 2+ and 2-. In occlusal sulcus type, H- was highest in occurrence. Many of the lingual cusps were positioned mesially and those positioned centrally followed. The first premolars tending to caninize in morphology accounted for 17.4%. 2. In comparison with the first premolars, growth of the lingual cusp of the mandibular seocnd premolars was good and many were types 2+ and 3-. In occlusal sulcus type, H+ was highest and type Y followed. Appearance of the distal lingual accessory cusps accounted for 38.5%. Consequently, the position of the lingual cusps further deviated mesially. 3. In the measurements of the mandibular premolars, the first premolars were longest in length and the second premolars were largest in thickness of the crown. 4. In the correlation of traits among the mandibular canines, the first and second premolars, correlation between the first and second premolars was highest, and between the canines and first premolars next. Almost no correlation was recognized between the canines and second premolars. 5. In the correlation of traits between the mandibular first premolars and second premolars and first molars, close correlation was recognized between the first and second premolars, but no correlation was recognized either between the first premolars and first molars, or between the second premolars and first molars. 6. In the bucco-lingual distance and mesio-distal distance of the crown, significant positive correlation was recognized among the canines, premolars, and molars. 7. On the basis of the foregoing, it was concluded that the first premolars possess morphological features of the canine, and that the second premolar does not possess the morphological features of the molar to the same degree.
- 九州歯科学会の論文
- 1981-09-25