咬合の衛生学的研究 等高線図法による上下顎第1大臼歯間の対向関係について
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概要
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For the study of dental occlusion in the light of oral hygiene, it is necessary to elucidate fully the antagonistic relationships between the upper and lower teeth and their contact conditions. Although there is a relative abundance of published research literature on these matters, what is to be accepted as conclusive is still scanty. A proper understanding of the relationships between the upper and lower teeth is particularly important for the determination of masticatory efficiency but, so far, many methods of determination are by no means uniform and reported data are at variance with one another.<BR>As a first step toward a better understanding of the masticatory efficiency from a hygienic point of view, the author studied the antagonistic and occlusal relations of teet in terms of cast models and carefully reproduced their curved planes on sheets of paper by the use of a contour map technique. The present study consequently brought out the following conclusions.<BR>1. A comparison of the plane and stereoscopic photographs in terms of the precision of measuements revealed that errors were much fewer in the latter. Therefore, stereoscopic photography is recommended for the photographic measurement of cast models.<BR>2. A benchmark axis was established for the upper and lower molars for the determination of their observational direction.<BR>Efforts were made made by a projection to find out how much inclination of this axis would occur to the buccloingual side at the eruption. As a result, it was found that, on the average, the upper first molar inclined to the buccal side by 8.0° and lower first molar to the lingual side by 15.0°.<BR>As there is a difference of 7.0° betweem the two, it can be seen that these two teeth invariably erupt in the same direction.<BR>3. The section sheets of contour lines were prepared with certain standards by overlapping the contour planes of the lower and upper first molars at the centric occlusion. In terms of the section sheets of contour lines thus prepared, there were, on the average, 6.3 contacts between the two including the point and suface contacts.<BR>4. When the antagonistic distances were compared between 2 lingual cusps of the upper first molar and 3 buccal cusps of the lower first molar, the measurements were as follows.<BR>Lower cesial buccal cusp top 0.15mm<BR>Upper mesial lingual cusp top 0.28mm<BR>Upper distal lingual cusp top 0.38mm<BR>Lower distal buccal cusp top 0.42mm<BR>Lower distal cusp top 0.58mm<BR>As is seen from the above values, the top of the lower mesial buccal cusp is in the most intimate occlusion.<BR>5. By the application of a contour line technique, it has been possible to portray graphically various spots of the teeth that are in intimate occlusion, in partial occlusion and those spots which are not in occlusion at all. At the same time, destances and antagonistic relationships can be numerically given.
- 有限責任中間法人 日本口腔衛生学会の論文