Bacterial contamination as a factor influencing the toxicity of materials to the exposed dental pulp.

Three materials, which had been previously found to be toxic when applied as pulp-capping agents in conventional rat molar pulps, were retested in germ-free rats. All produced much more favorable responses in the pulp, with a lack of inflammation and the presence of dentine bridges in the majority of teeth. It appears that much of the pulp damage previously attributed to the chemical toxicity of materials may be caused by the presence of bacteria. The design of studies intended to evaluate the response of the pulp to materials should include staining techniques that will detect the presence of bacteria on the floors of test cavities.