Experimental gingivitis in the monkey

Rhesus monkeys receiving an oral hygiene program which included brushing, interdental cleansing and topical applications of chlorhexidine gluconate demonstrated a clinically normal gingiva for periods of up to 3 months. Wide fluctuations within individual dental units were noted with respect to histological sulcus depth, degree of connective tissue infiltration with lymphocytes and plasma cells, and total leukocyte or polymorphonuclear leukocyte (PMN) counts in the Junctional epithelium, even when the plaque and gingivitis index scores were 0. Of 18 clinically normal dental units sampled, only 6 appeared free of connective tissue inflammation. However, more than half of the tissue blocks obtained from dental units with a gingivitis and plaque index of 0 also showed scores of 0 with respect to the connective tissue inflammation (CTI) score and the number of PMNs in the Junctional epithelium. Within three days following discontinuation of oral hygiene procedures, rhesus monkeys developed a clinically noticeable gingivitis which began in the interdental papillae. Increases in CTI scores and number of leukocytes in the Junctional epithelium were evident after 2 days without oral hygiene. These values tended to increase further during the experimental period. A slight, but significant increase in sulcus depth was also noted during this time period. Regardless of the clinical state of the gingiva, a positive correlation was established between CTI scores and the number of PMNs and leukocytes in the Junctional epithelium. In early gingivitis, the plasma cells did not appear to outnumber lymphocytes, as has been reported for chronic gingivitis of longer duration.