下顎小臼歯に出現する根面溝の形態学的研究
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概要
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It has been shown that there is a groove on the mesial or buccal root surface of the mandibular premolar in human. When the groove is formed deep, the root bifurcates or trifurcates and presents complicated morphology. There have been many studies done on racial variations in the frequency of appearance of this groove. The morphology and location of this groove therefore were studied to obtain information for dental treatment. Of a total of 2, 557 mandibular premolars used, 226 teeth (108 first premolars and 118 second premolars) classified by Okumura's (1914) into 4 types, Aa1, Aa2, Ab1 and Ab2, with deep grooves on the mesio-lingual surface of their roots were examined. The results were as follows. 1. The average length of the lingual groove is 10.63 mm in the first premolar and 10.53 mm in the second premolar. They are 80.0% and 77.8% of their root length. 2. The lingual groove is located 2.26 mm from the lingual edge in the first premolar and 2.24 mm in the second premolar. They are 32.4% and 31.4% of the bucco-lingual diameter. 3. The buccal grooves appear in 81.5% of the first premolar and in 47.5% of the second premolar. The average length of the grooves is 7.55 mm in the first premolar and 7.25 mm in the second premolar. They are 57.8% and 53.5% of their root length. 4. The distal grooves appear in 25.0% of the first premolar and 19.5% of the second premolar. The average length of the grooves is 7.88 mm in the first premolar and 7.61 mm in the second premolar. They are 60.0% and 56.1% of their root length. 5. The buccal grooves were observed in 3.7% of the first premolar and 5.9% of the second premolar. The average length of that groove is 9.70 mm in the first premolar and 8.89 mm in the second premolar. They are 73.9% and 66.2% of the root length. 6. Many of the first premolars have two grooves on their mesial surface (55.5%), as in the second premolars (47.5%). 7. The root ridges were observed on the mesial surface in the first premolar (94.5%) and in the second premolar (91.3%). They were also observed on the distal surface in the first premolar (38.8%) and the second premolar (22.8%). The tooth that has deep grooves on the mesial surface has distal ridges as well as mesial ridges. 8. There is a significant relationship between the length of the mesio-lingual groove and root length. There is also relationship between the bucco-lingual diameter and the distance from the lingual edge.
- 九州歯科学会の論文
- 1996-10-25