Microbiological assessment of dental plaque on bovine enamel implants worn intra-orally in children.

Nine caries-active children, each from six to nine years old, wore small removable enamel implants intra-orally for four weeks as part of an effort to develop removable model systems for studying dental plaque in fissures. The implants, consisting of two enamel cubes arranged to simulate a fissural space, were cemented in box preparations in stainless steel crowns on pulpotomized primary molars. Upon removal, the fissural spaces were opened to facilitate plaque harvesting. The plaque samples were cultured, and enamel decalcification of the plaque-exposed surfaces was measured. Quantitative microbial values were compared with those of natural fissure plaque samples from both caries-active (CA) and caries-and restoration-free (CF) children, also from six to nine years old. Streptococcus mutans and S. sanguis levels of fissural insert plaque (FI) and natural fissural plaque from (CA) were similar. Both contained higher S. mutans levels than did plaque from (CF). FI harbored higher concentrations of Lactobacillus and Actinomyces species and lower concentrations of Neisseria species. Otherwise, FI plaque resembled natural fissure plaque. Microhardness of FI plaque-exposed enamel decreased significantly compared with pre-experimental values and showed a significant negative correlation with values for total lactobacilli on selective media, and for S. mutans on non-selective media.