Effects of excessive occlusal loading on the periodontium of splinted teeth in Rhesus monkeys
Mafla, Emilia R.
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An investigation was undertaken to study the effects that fixed prosthetic appliances, which increased the vertical dimension of occlusion, could produce on the periodontal structures of splinted teeth in Rhesus monkeys. Six female Rhesus monkeys were chosen and divided into two groups: Group A. included two animals in which an increase of the vertical dimension of occlusion was effected along the entire splints, keeping flat occlusal planes. Group B. included four animals in which the vertical dimension of occlusion was increased at the same level as in Group A but in the form of a prematurity in the normal path of closure. The prematurity was located on the lower first molars. Perfusion with filtered Pelikan carbon black suspension, (Gunther-Wagner), was done at the time of sacrifice in order to visualize the blood vessels, their degree of patency, distribution, perviousness and thus injury. The following observations were made in the overall histologic study: 1. There were significant alterations of the attachment apparatus around all the splinted teeth bilaterally -upper and lower-. 2. The furcations and the apical regions were the most affected areas in all the animals of both groups. 3. A direct intrusional force was noted in the animals of Group A in which resorption affected a more extensive length. However these animals presented more evidence of repair process than animals in Group B. 4. The splinted teeth acted as a unit because the rigid splinting method employed. 5. The monkeys in Group B also manifested resorptive changes in the interdental septa apparently produced by direct pressures. 6. The splinted teeth were intruded, a finding in agreement with Ramfjord’s studies (71,72). At the end of the experiment there was posterior occlusal contact in all the animals. 7. In contrast to Glickman’s study (40), where only the interradicular areas were affected, we noted the interdental septa as well as the furcas and the apical regions were also severely resorbed in the monkeys of Group B. 8. It is worthy of note that we did not observe cemental teras as reported in several studies of occlusal trauma (8-25,55) nor found inflammation spreading directly from the gingiva into the periodontal structures in contrast to Glickman's observations (64 ). 9. Clinically, there was a decrease of approximately 4mm. in all animals from the initial experimental vertical dimension of occlusion in the region of the first molars.
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