[Anatomic changes of the posterior alveolar ridge and external oblique ridge area in human mandibular edentulous specimens].

In this research the posterior alveolar ridge and the external oblique ridge area of 103 mandibular specimens of adult subjects-122 sides with teeth intact and 62 sides with edentulous ridge were measured in different items. The dissection of the external oblique ridge area in 7 cadavers was made and observed. The results showed: (1) the atrophy of residual alveolar ridge of the mandible is severe than that of the maxilla; (2) the resorption of the buccal alveolar plate is more than that of the lingual plate; (3) the resorbed buccal portion of the mandibular alveolar ridge is replaced by the external oblique ridge area, so that the latter becomes wider and flatter. This change of form is beneficial for the denture support and the extension of the buccal flange of the lower denture. The data of the resorption of the buccal alveolar plate provide the reference of the arrangement of the posterior teeth of the lower complete denture. Consequently, we may conclude that the external oblique ridge area is utilizable and beneficial for the support and stability of the lower complete denture.