[Effect of systemic oral administration of tetracycline on experimental gingivitis in golden hamsters]

Local and systemic administrations of tetracycline have been used in human periodontal treatment for conditions including juvenile periodontitis and rapidly progressive periodontitis, although microbiological effects of the treatment have not been clear. The effect of systemic oral administration of tetracycline on subgingival bacteria in experimental periodontal disease in hamsters as an animal model has not yet been reported. The aim of this study was to investigate changes in subgingival bacteria and bone resorption at the lower left first molar, and supragingival plaque formation on the lower right first molar in animals with (TC group) or without (Diet-2000 group) systemic oral administration of tetracycline hydrochloride 25 mg/kg/day in 20-day-old golden hamsters that mere fed a high sucrose diet (Diet-2000). Experimental periods were established as 15, 29, 43, 57, and 71 days. Supragingival plaque formation on the lingual surface on the lower right first molar in the Diet-2000 group gradually increased with time; that in the TC group was scarce and was not increased with time. Bone resorption at the lower left first molar in the Diet-2000 group proceeded rapidly with time, while that in the TC group was scarce. Total number of bacteria from subgingival plaque on the lower left first molar in the Diet-2000 group increased rapidly with time, but that in the TC group did not vary at all with time. Actinomyces (Actinomyces naeslundii and Actinomyces viscosus) and Bacteroides (Bacteroides capillosus and Bacteroides ruminicola subsp. ruminicola) in the Diet-2000 group increased with time; those in the TC group decreased with time. A remarkable difference in IgG titers to Bacteroides asaccharolyticus was not observed in the Diet-2000 and the TC groups. These results suggest that systemic oral administration of tetracycline hydrochloride on experimental gingivitis in golden hamsters causes the total number of subgingival bacteria to be confined, and to be decreased species of Actinomyces (Actinomyces naeslundii and Acinomyces viscosus) and Bacteroides (Bacteroides capillosus and Bacteroides ruminicola subsp. ruminicola), leading to the inhibition of bone resorption and supragingival plaque formation. It is suggested that Bacteroides asaccharolyticus is not a pathogen concerned in experimental periodontal disease in hamsters, because the antibody titer was not elevated in the Diet-2000 group.