NONHUMAN-PRIMATES USED IN STUDIES OF PERIODONTAL-DISEASE PATHOGENESIS- A REVIEW OF THE LITERATURE

THE INABILITY TO EXAMINE INITIATION AND PROGRESSION of periodontal dis ease and to assess certain therapies in humans has led to a great inte rest in the use of animal models in periodontal research. Some of the most prominent animals used are non-human primates. This article revie ws the characteristics of non-human primate models in periodontal heal th, in the transition from health to gingivitis to periodontitis, and in experimental gingivitis and periodontitis. Where possible, the resu lts of these studies are compared with results from human studies. Onl y a few studies have compared in detail the anatomy, physiology, immun ology, and tissue interactions in monkeys with those of humans. With t he exceptions of differences and variations in size of the dentition, the number of each tooth type as well as larger canines, presence of d iastemata between anterior teeth, and an edge-to-edge relationship of the incisors, the dental and periodontal anatomy of nonhuman primates seem quite similar to that of humans. Clinically healthy gingiva can b e established and maintained in non-human primates, and gingivitis as well as periodontitis occur in these animals. It is possible to induce experimental periodontitis by placement of peri-dental silk ligatures or orthodontic elastics as well as by surgical removal of alveolar bo ne. Although the most appropriate model for studies of periodontal dis ease pathogenesis in non-human primates appears to involve the applica tion of silk ligatures, some difficulties may occur in establishing pe riodontal break-down by using this model. Many clinical, histological, microbiological, and immunological characteristics of spontaneous and experimental marginal inflammation in most non-human primates are sim ilar to those in humans. The most significant differences between smal l non-human primates and humans are the very limited number of lymphoc ytes and plasma cells in the inflammatory infiltrate of squirrel monke ys (Saimiri sciureus) and marmosets. Therefore, the use of squirrel mo nkeys and marmosets may not be appropriate in many studies of periodon tal disease pathogenesis. The most significant microbial differences b etween macaque species and humans are a lower proportion of Actinomyce s species, the presence of a catalase-producing Prevotella melaninogen ica strain, and the high carrier rate for Actinobacillus actinomycetem comitans in subgingival plaque of macaque species. The significance of these differences is presently unknown. It is concluded that the use of many non-human primate species due to the apparent close anatomic a nd biologic similarities to humans is appropriate in experimental stud ies of periodontal disease, provided the use of laboratory animals is requisite and lower species are not applicable. The increasing use of captive-born instead of wild-captured primates as laboratory animals w ill eliminate many of the problems that plagued researchers heretofore due to greater homogeneity in age, body weight, and dental health sta tus combined with a known medical story of captive-born animals.