抄録
The present study has been carried out to reveal the changes in the form of the pars alveolaris mandibularis and the basis mandibulae after extraction of teeth. The materials used in this study were the same as previously reported, namely seventy-four mongrel dogs which were divided into eight groups and two subgroups according to age, sex, number of extracted teeth and time after extraction of the teeth. On their mandibles the most dorsal and the most ventral point of the mandibular body, representing the pars alveοlaris and the basis mandibulae, were observed on the basis of the co-ordinates in order to elucidate their buccolingual and dorso-ventral shift on account of the loss of teeth. According to our observations, the following conclusions appear justified: The residual ridge shows a remarkable decrease of height against the alveolar ridge before extraction of teeth, and the crest of the residual ridge lies at the buccal side of the lingual alveolar crest on the lower first and the lower second molar portion, but it is located lingually to the lingual alveolar crest on the lower fourth premolar portion. The most ventral point of the basis mandibulae shifts ventrally and buccally in the growing, but in the mature it appears to move dorsally and lingually after the teeth have been removed. The degree of changes in form of the pars alveolaris and the basis mandibulae was higher in the growing than in the mature. But there is no significant difference between the male and the female, and also between the groups extracted on the lower first molar and on all lower posterior teeth. In the growing the form of the pars alveolaris and the basis mandibulae changes significantly in six months after extraction of teeth, but afterward ceases to change. In the mature, however, it remains mostly variable before twenty four months pass.
