上顎において歯牙が無理なく萌出できる後方限界点の研究
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概要
- 論文の詳細を見る
The present study was an analysis of horizontal growth of the permanent dentition. As a step of the analysis, measurements were undertaken to establish the posterior limit of upper jaw within which could be placed all the erupting teeth with stability, utilizing a series of gnathostatic plaster models on 105 patients of the children, 54 boys and 51 girls. Each child was observed during a period of 6 to 15 years, covering the transition from the primary to the secondary dentition. As shown diagram, each distances from Point a, m, n, to Point c and from Point I, m, d to Point a, were measured respectively. Point c was designated as "Iinea terminalis posterior gingivae" boundary line which served to demarcate the mucous membrane lining pterygo-maxillary incision into immovable (gingival part) and movable (alveolar part) by T. Akiyama (1969), who was observed in detail with regard to those of lower jaw. Results obtained were summarized as follows. 1) The distal migration of position of Point c with increasing age was yearly average 1.0mm in male, 0.9mm in female. 2) More than 70% of the subject showed a spurt of individual growth of the maxilla during a period of 10 years and 3 months to 13 years and 3 months of age. 3) Growing rate of the maxilla was the highest during a period of 9 years and 4 months to 10 years and 3 months of age, regardress of the sexes and individual difference in size of jaw of the subjects. 4) When the distance between Point n (future distal contact point of hindermost molar) and Point c was under 3.0mm, the presenting dentition appeared to be irregularly positioned, showing such jaw was small in size to accomodate all the teeth to erupt. 5) It was comfirmed that when the distance between Point n and Point c was over 3.5mm, all the erupting teeth could be placed with stability within upper jaw. 6) Mesial migration of hindermost molar occurring with convenient extraction of forward tooth was by no means limitless, approximately maximum 4.0mm. 7) When hindermost molar was erupted forcibly, in spite of that the distance between Point n and Point c was insuffient for the tooth, Point c was migrated backward from the last molar. These evidences pointed to the conclusion that the "linea terminalis posterior gingivae" (Point c) could serve as a criterion to determine the posterior limit in the measurement of the magnitude of apical base of upper jaw as well as lower jaw and that any stable eruption of the hindermost molar should come 4.0 mm far mesially from this limit.
- 九州歯科学会の論文
- 1974-09-30