ヒトの隣在臼歯における接触局面の研究

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The proximal surfaces of the neghibouring posterior teeth in young person keep in contact with each other on the contact point, but as ages advance, it changes from contact point to contact facet. The observation with the naked eye on the contact facets were only made by the former researchers and clinicians on the position, form, size and frequency of the contact facets formed on the proximal surface of the extracted teeth and the casts used in clinic. In this study, the subjects were 432 posterior teeth, in 756 teeth specimen of 27 male individuals, which are anatomically normal, in number 28 proximated teeth at least and standard dentition and occlusion can by reproduced from their proximal facets. And they were divided into two groups (1) younger group ages of 24 to 44 and (2) older group ages of 45 to 65. The frequency of the proximal facets of each proximal surface of each posterior tooth were examined. On the projection chart enlarged 7 times as large with the use of Shimazu all-round microscopic projection device, their position, form and area were observed, furthermore, the area of the proximal facets were measured by planimeter and the surface condition were calculated from the measurement of the concave, convex and wavelike that were enlarged 100 longitudinal magnification and 50 transverse magnification with the use of Yamamototype roughness tester. Special attention has been paid to the correlation of the position, form, area and surface condition of the two adjacent proximal facets that stand face to face, and the following results were obtained. 1. The contact facets were found wholly, in the distal proximal surfaces of the first premolar in the mesical and distal proximal surface of the second premolar and molars, though inthe mesial proximal surfaces of the first premolar only point contacts were observed in a few cases, about 9 %. In their frectuency the difference between upper and lower Jaws, and right and left sides were statistically not significant in the same named proximal surfaces of the identicalteeth. 2 In the form of contact facets bucco-lingually ellipse form were in the most (about 72 %), kidneysharped form, ovoid form and triangle form were a few in all posterior teeth and tapering-ovoid form, quitar-shaped form and quadrangle form were few. It was a trend that ellipse form were found many throughout younger and older groups, ovoid form were found mostly in the lower premolars of younger group and kidney-shaped form were found mainly in the molars of older group. 3. Tn the opposing correlation of the form of the two adjacent contact facets, ellipse form to ellipse form (one of the types that two same form oppose), gained a majority (about 60 %), ellipse form to kidney-shaped form (one of the types that two different form oppose), was a few (about 12 %), ellirse to triangle (about 6 %) and ellipse to ovoid (about 5 %) were few each. It was a trend that ellipse form to ellipse were found many throughout both groups and ellipse to kidney-shaped and kidney-shaped to kidney-shaped were found mainly in older group. 4. In existing position of contact facets they gained a majority in the bucco-lingual occlusal surface area (about 57 %), they were a few in the buccal occlusal surface area (about 17 % ) and in all areas of the proximal surfaces (about 12 % ). It was a trend that the contact facets were found many in the bucco-lingual occlusal surface area in both younger and older groups, those in buccal occlusal surface area were found mostly in the upper premolars of younger group and those in all areas of the proximal surfaces mostly in the surfaces between the first and second molars of younger and older groups. 5. In the opposing correlation of the existing positions of the two adjacent contact facets the type opposing in same areas gained a majority (about 54 %, and about 1/4 of those in the bucco-lingual occlusal surface area, about 1/7 in the buccal occlusal surface area and about 1/8 in all areas of the proximal surfaces) and the type opposing in different areas were found fewer than the former (about 1/3 in the bucco-lingual occlusal surface area to buccal occlusal surface area, about 1/3 in the buccal occlusal surface area to all areas and about 1/7 in the bucco-lingual occlusal surface area to lingual occlusal surface area). 6. The cases that the proximal contact facets reaclaed to the marginal ridges of the occlusal surface were in the majority and more than those that the facets did not. In a few cases the contact facets reached to the buccal ridges but none of them reached to the lingual ridges. In their frequency the difference between upper and lower jaws, and right and left sides were not significant in the same named proximal surfaces of the identical teeth. 7. The area of contact facets was about 3 mm^2 in the mesial surface of the premolar, about 4 mm^2 in the distal surface of the premolar, about 6 mm^2 in the mesial surface of the molar and 6.5 mm^2 in the distal surface of the molar. The area increased, as ages advarace. The difference of the area between upper and lower jaws, and right and left sides were statistically not significant in the same named proximal surfaces of the identical teeth. It wasa trend that the area of the opposting contact facets of the neighbouring posterior teeth in the mesial surfaces of the more posteriorly positioned were larger than those in the distal surfaces of the more anteriorly. 8. In the surface condition of contact facets the concave (concave value-about 30〜230,μ) gained a majority (about 60 %), the wavelike (concave value 20〜140μ, convex value-about 20〜120μ) and the convex (convex value-about 20〜220μ) were a few each. The flat type were found in the minority mainly in the mesial surfaces of the first premolars of young group. It was clear that in older group the concave decreased and the wavelike increased. In their frequency the difference between the upper and lower jaws, and right and leftsides were statistically not significant in the same named proximal surfaces of the identical teeth. 9. In the opposing correlation of the two adjacent surface condition of contact facets the type opposing in the same form (concave to concave) and the type opposing in the different form (concave to convex) were almost the same and those two types together gained a majority (about 63 %) and the type of concave to wavelike were a few (about 18 %). The type of wavelike to wavelike were a few mainly in older group. In their frequency the difference between upper and lower jaws, and right and left sides were statistically not signifficant in the same named proximal surfaces of the identical teeth.
社団法人日本補綴歯科学会の論文
1969-06-30

著者

熊切慶
日本大学大学院歯学研究科補綴学専攻

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