[Morphological study on edentulous mandibula].

For the purpose of studying morphology of edentulous mandibula, not only the bone change of edentulous alveolar part, but the whole morphological change of edentulous mandibula was examined. Thirty-three edentulous mandibulae that have no sockets owing to the bone absorption of alveolar ridge and eighty dentulous mandibulae that possess no missing teeth except wisdom teeth were measured and compared. The authors obtained the following results concerning the morphological change of edentulous mandibula: 1. Although the body height was significantly low on account of bone absorption at the alveolar ridge, bone absorption at base of mandibula was not much observed. 2. Both condylar process height and coronoid process height were significantly low. 3. Mandibular angle of edentulous mandibular was greater. 4. In dentulous mandibula a negative correlation between mandibular angle and condylar process height, coronoid process height was found. A correlation between mandibular angle and the difference of total mandibular length and body length was observed. A great mandibular angle was found because it seems that the bone deposition was less at the inferior and posterior margin of mandibular angle part. 5. It seems that bone absorption at inferior and posterior margin of edentulous mandibular angle part was due to less bone deposition. Because a bite force decreased for missing teeth.