Regional differences in the detection rate of periodontopathic bacteria in supragingival plaque

Although there are numerous reports on detection of bacteria causing periodontal diseases within the oral cavity, most of these treat the oral cavity as a single entity. The objective of this study was to determine whether there was site-specificity in the detection of certain bacteria in supragingival plaque from different regions of the oral cavity. The subjects were six adults with no recognized oral problems. We examined eight regions; the labial and lingual surfaces of the upper and lower anterior teeth and the upper and lower first molars. The target bacteria included five species of bacteria that cause periodontal diseases. After professional medical tooth cleaning (PMTC), the volunteers performed no oral prophylaxis for three days. Then we collected about 1 μl of plaque from each of the regions by excavators. We searched for the five species of bacteria by immunoslot-blot assay and compared the results from the respective regions. We discovered that the detection rate was very small for all five bacterial species on the lingual surface of the lower anterior teeth, which is known to have good salivary clearance. On the labial surface of the upper anterior teeth, which is commonly believed to have poor salivary clearance, the detection rate was higher but there was no specificity with respect to detection rate. The regions with the highest detection rates were the buccal surface of the upper and lower molars. On the lower molars, larger populations of Porphyromonas gingivalis and Prevotella nigrescens were detected. On the upper molars, Prevotella intermedia and Prevotella melaninogenica were detected. These results suggest that there is regional specificity in the presence of periodontopathic bacteria in the mouth.