Microbiological and microhardness evaluation of artificial enamel fissures worn intraorally by humans

Devices simulating occlusal fissures were constructed from dental enamel and bonded to human maxillary molar teeth for 3 weeks. Facilitation of in vivo caries research in humans is the long-range goal for this model system. In the present investigation, microbial compositions of plaque in the fissural space of the model and natural fissural plaque from teeth bearing the devices were compared. Plaque from models constructed from either bovine or human enamel was also compared. In addition, microhardness of the enamel surfaces was examined before and after oral exposure. Plaque in both bovine and human enamel models differed significantly from natural fissural plaque in several microbial categories. Differences appeared to be related to the increased accessibility of the deep fissural contents of the models. For example, levels of the aciduric Streptococcus mutans and Veillonella species were higher in the models, although levels of a salivary inhabitant, Streptococcus salivarius, were lower. Plaque in bovine and human enamel models was similar, and both models showed significant decreases in enamel microhardness after oral exposure for 3 weeks. The model system should be useful in caries research in that carieslike activity was simulated within a relatively short period of time, and the fissural space became colonized by high levels of cariogenic bacteria.