Bacterial contamination and the "toxicity" of materials to the exposed pulp

The role of bacterial contamination in the toxicity to the pulp of a number of metallic salts was investigated. These had been tested as pulp-capping agents in previous studies involving 228 exposed rat molars. Material from the previous investigations was stained to demonstrate bacteria. This revealed bacteria in necrotic pulp tissue and/or the cavity-restoration interface in approximately 60% of the specimens. The presence of bacteria appeared to be related to pulpal inflammation, necrosis, and failure of calcific repair.