洋犬の歯, とくに後臼歯についての計測学的研究
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概要
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Measurements were taken of the length and width of the head with use of dog skulls of Western Breed preserved in the First Department of Oral Anatomy, and the ratios of the two, or cephalic indexes were determined. Classifications based on the indexes were obtained in three types : dolichocephalic type (under 40), mesocephalic type (40-70), and brachycephalic type (over 70). For the present study, the teeth were measured of 30 cases of the mesocephalic type and 10 cases of the brachycephalic type, and a study was made of the measurements. Especially the correlation between the size of cusps and the extent of growth of the distomolars was studied. The results were as follows : 1. For all the teeth, the height, width and thickness of the mesocephalic type were greater than those of the brachycephalic type. 2. In the incisors, the mesial teeth were smallest. Closser to the distal side, the larger were the incisors. In the molars, each carnassials was largest. Further away from it, mesially or distally, smaller the teeth in order. The maxillary and mandibular first premolars and the mandibular third distomolars, in particular, were exceptionally small. 3. In the relation between the width and thickness of the crown, almost no differences were found between the maxillary and mandibular incisors and the maxillary distomolars. In the other teeth, the width was greater in comparison with the thickness. This finding was significant in the mandibular first distomolars (carnassials) in particular. 4. In determining the extent of growth of the talon in the maxillary distomolars by comparing the indexes of width and thickness with the trigone, the width was about 70% of the trigone. The percentage was greater for the brachycephalic type than for the mesocephalic type. The second distomolars were greater in index than the first distomolars. The thickness was only about 18% of the trigone. Mesocephalic type was greater in index than brachycephalic type. The first distomolars were greater in index than the second distomolars. 5. The height of hypocone against paracone of the maxillary distomolars was about 50%. 6. In the mandibular distomolars, the talonid was well grown, and its width against that of the trigonid was about 30% in the first distomolars and about 38% in the second distomolars. The latter was comparatively larger. Those of the mesocephalic type were greater than those of the brachycephalic type. 7. In the mandibular distomolars, the talonid was about 90% of the trigonid in thickness. Its thickness was larger in the first distomolars than in the second distomolars. The thickness was larger in the mesochephalic type than in the brachycephalic type. 8. The height of each cusp of the crown of the mandibular distomolars was compared with the others. Against the highest protoconid in the center, hypoconid positioned posteriorly to it, was about 56% in height in the first distomolars and about 63% in the second distomolars, whereas paraconid positioned anteriorly was about 90% in the first distomolars and about 75% in the second distomolars.
- 九州歯科学会の論文
- 1981-09-25