Experimental gingivitis in man

Twelve male dental students with healthy gingiva were subjected to a 3 week period without oral hygiene. During this period 6 subjects rinsed their mouth 3 times daily with a 0.5 per cent solution of vancomycin, while 6 subjects rinsed with distilled water. In both groups gingival plaque accumulated rapidly and after 3 weeks all participants developed gingivitis. Clinically no difference could be detected between the two groups. The microflora of the plaque accumulating in the group rinsing with water developed according to the pattern observed in previous investigations. In the vancomycin group this pattern was not followed. Gram-positive bacteria did not proliferate, and after 5 days rinsing with vancomycin only gram-negative bacteria were seen in stained smears and impression preparations. Spirochetes were never observed. In cultures of bacterial plaque a few gram-positive bacteria were found in most but not all of the samples collected at intervals during the experimental period from subjects in the vancomycin group. It is concluded that a predominantly gram-negative bacterial flora is able to form plaque and elicit gingival inflammation in humans.