[Morphological characteristics of the alveolar ridge of edentulous jaws]

Impression taking is essential step in prosthetic clinical work and a tray of an appropriate size and form must be selected to obtain accurate impressions. In taking impressions of edentulous jaws, in particular, the morphology of the alveolar ridge must be grasped precisely. Length and width of the alveolar crest therefore were measured and their correlation was examined. 1. The coefficients of correlation of the maximal length of the alveolar crest with width between the posterior margins of the alveolar crest, with the width between the alveolar crest at the first molars, and with the width between alveolar crest at the canines were r = 0.20, 0.43, 0.38, respectively, for the upper jaws, and r = 0.14, 0.01, 0.02, respectively, for the lower jaws. No significant correlation was found. 2. Significant correlation was found between the posterior margins of the alveolar crest and the width between the alveolar crest at the first molars and the width between the alveolar crest at the canines (r = 0.66, 0.70) for the upper jaws. 3. Significant correlation was found between the posterior margins of the alveolar crest with the width between the alveolar crest at the first molars (r = 0.76) for the lower jaws.