Morphometric Analysis of Crown Angulations in Elderly with Many Teeth

Objective:There are few reports on morphologic characteristics of teeth, dental arches and occlusion in elderly with many remaining teeth. The purpose of this study was to clarify the pattern of aging by quantifying the tooth angulation(tip) and thereby to identify factors contributory to aging and long-term stability. Methods:Dental casts of twenty 8020 achievers, aged over 80 with 20 or more teeth remaining, (10 males, 10 females, average age 82 years, average number of 28.2 remaining teeth) were digitized with a 3D laser scanner (VMS-100F), reconstructed into 3D images and measured with an analytical software. The occlusal plane formed by the incisal edge of the central incisor and distal buccal cusp tip of the first molar on either side was used as a reference plane to measure the mesiodistal tip of each tooth. The measurements were compared with those of adults with normal occlusion studied by Sebata-Motegi. Results:Mesiodistal crown angulations (indicated in degrees) of maxillary teeth in the 8020 achievers averaged 3.10 for central incisors, 4.91 for lateral incisors, 7.31 for canines, 5.17 for first premolars, 5.03 for second premolars, 3.04 for first molars, 4.23 for second molars and 6.01 for third molars. Average values of mandibular teeth were 3.91 for central incisors, 4.20 for lateral incisors, 6.57 for canines, 6.52 for first premolars, 5.41 for second premolars, 4.89 for first molars, 6.05 for second molars and 9.02 for third molars. The 8020 achievers showed significantly greater mesial angulations of the mandibular central incisors, lateral incisors, canines (p<0.001) and first premolars (p<0.01) than the adults with normal occlusion in Sebata-Motegi's study. Conclusion:Mesiodistal crown angulations were measured in 8020 achievers. The increased mesial angulations of the mandibular anterior and premolar teeth may the cause of thire lower incisors' crowding and respresent an aging phenomenon.