Reduction of viable bacteria in dentinal tubules treated with clindamycin or tetracycline

Aim. We sought to evaluate and compare the antibacterial effect of clindamycin and tetracycline in bovine dentinal tubules. Methods. Dentinal tubules of 32 cylindrical bovine root specimens were infected with Streptococcus sanguis N1. Clindamycin 2% or tetracycline 2% (Ledermix) was placed in the root canal for 1 week. Powder dentin samples obtained from within the canal lumina by using International Standards Organization No. 25 to No. 31 burs were examined for the presence of vital bacteria after the brain-heart infusion plates were inoculated and the colony-forming units were counted. The potent effect of the medicaments was also evaluated through the use of the agar diffusion test. Results. Heavy bacterial infection was observed in the control bovine root specimens at the layer close to the lumen. This decreased rapidly from layer to layer up to the deepest layer tested (300-400 μm), which contained several hundred colony-forming units. Clindamycin significantly reduced the amount of viable bacteria in each dentin layer compared with the positive control and tetracycline (P < .01). The agar diffusion test, wherein dilutions in increments of 1/3 and 1/9 were used, revealed that both medicaments had antibacterial activity, but clindamycin was significantly better. In the 1/27 dilution, clindamycin had a minor effect and tetracycline had no effect at all. Conclusion. Under the experimental conditions used in this study, the commercial preparations of clindamycin were more effective than those of tetracycline (Ledermix) in the agar diffusion test and clindamycin penetrated into dentinal tubules up to 400 μm. Thus, it has the potential to serve as an effective intracanal medicament in persistent infections when other medicaments fail.