上顎大臼歯における Enamel Projection について
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概要
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By the observations of the enamel projection on the buccal, mesial and distal surfaces of the maxillary molars, using 197 samples of maxillary first molar and 110 samples of the maxillary second molar, classifying them into five types according to the projection lengths, the author observed the appearance frequency of each type and measured the length of enamel projection, and have obtained following conclusions : 1. The appearance frequencies of the enamel projection in the maxillary first molar are 77.7% on the buccal surface, 46.8% the mesial surface and 43.2% the distal surface. In the maxillary second molar, they are 93.3% on the buccal surface, 71.8% the mesial surface and 71.0% the distal surface. The frequency relating to each of the respective surface is significantly greater in the second molar than the first molar. 2. The frequency in the first molar is of such order as the Type 2 : 43.7%, Type 3 : 23.9%, Type 1 : 22.3% Type 4 : 9.6% and Type 5 : 0.5% on the buccal surface, indicating significant differences between the Type 2 and 3, Type 4 and 5. Only Type 1 : 53.2% and Type 2 : 46.8% appear on the mesial surface, and on the distal surface three types only, or Type 1 : 56.8%, Type 2 : 42.6% and Type 3 : 0.5%. In the maxillary second molar, such frequency order as Type 2 : 40.0%, Type 3 : 30.9%, Type 4 : 20.9%, Type 1 : 6.4% and Type 5 : 1.8% on the buccal surface is seen but the difference between the types is not significant. On the mesial surface, 71.8% of Type 2 is evidently greater than the only remaining Type 1 : 28.2%. Also on the distal surface is seen as same as on the mesial surface at all, Type 2 : 71.1% and Type 1 : 28.9%. 3. In the observation of the type combination of each surface, the combination of Type 2 of the buccal surface and Type 1 of both mesial and distal surfaces is the foremost with 22.9% in the first molar. In the second molar, the combination of type 2 in all of the buccal, mesial and distal surfaces is the foremost with 29.2%. 4. The lengths of the enamel projection on the buccal surface of the first molar are 0.97mm for Type 2, 2.79mm : Type 3 and 3.38mm : Type 4. In the second molar, Type 2 is 0.86mm long, Type 3 : 2.53mm, and Type 4 : 3.77mm. 5. Observing together with the appearance frequencies of the enamel projection in the mandibular molars reported by the author et al. in 1969, the appearance of enamel projection in the second molar, the closer one to the distal end of the dental arch, is more frequent than in the first, then this paper suggests to me, that may have some inter-relationship with the dental degeneration.
- 九州歯科学会の論文
- 1977-03-31
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