Plaque from labial and approximal sites on the maxillary and mandibular incisors of 23 subjects was inoculated into broth and incubated for 72 h. The broth was plated to selective media and the presence of several microbial components of the flora determined. Lactobacilli, the most aciduric of the bacteria isolated, were mainly found in plaques on the maxillary approximal surfaces, the most prevalent species being Lactobacillus casei. The less aciduric streptococci usually occurred in the labial maxillary plaques, with Streptococcus mitis the most common species. Gram-negative filaments, including Fusobacterium sp., Leptotrichia buccalis and the Gram-positive microorganism Bacterionema matruchottii, were usually observed in plaques from the mandibular approximal sites. Veillonella were more frequent in mandibular than maxillary plaques, whereas Actinomyces showed no site preference. The findings support the view that saliva, by its effect on plaque pH, significantly influences plaque microbial composition. © 1979.
