Photoelastic analysis of pressure on teeth and bone supporting removable partial dentures

The direction and pattern of forces delivered to teeth, periodontal membrane, and bone supporting a removable partial denture can be demonstrated by reproducing the dental arch in a photoelastic plastic material. Occlusal forces delivered to tooth-supported and distal-extension removable partial dentures produced repeatable patterns in the supporting structures. Physiologic adjustment of the metal contacts against the teeth on distal-extension removable partial denture castings is necessary to minimize tipping and torquing movement.     

Age-related changes in the periodontium of pigtail monkeys

Age-related changes in the periodontia of maxillary lateral incisors were studied in the pigtail monkey (Macaca nemestrina) . Transverse sections were obtained from the crestal and apical middle third of the roots from specimens of ages 3 and 4 years (N = 2), 10 years (N = 3), and 20 years (N=3). With increasing age, the roots migrated toward the labial cortical plate, resulting in the development of a bony root prominence on the labial periosteal surface. Quantitative histomorphometric measurements in conjunction with analysis of variance were used to isolate the effects of age and section level on the parameters of interest. The areas of the alveolar socket and cementum increased significantly with age, as did cemental thickness. The width of cementum on the lingual surface was significantly greater than the width on the other surfaces, probably as a response to the labial migration of the tooth. The width and relative area of the periodontal ligament space decreased significantly with age, suggesting that the deposition of cementum proceeded at a rate slightly greater than that at which the socket was enlarging. The number of blood vessels in each quadrant of the periodontal ligament were counted, and no significant difference was found among the different age groups. There were, however, significantly more blood vessels in sections from the crestal third than in those from the apical third of the roots.