Bacterial morphotypes of 3-day old plaque in Chinese. A pilot study

The aim of the this study was to estimate the % distribution of bacterial morphotypes of supragingival plaque in Chinese subjects after 3 days of no oral hygiene. 36 dental students, hygienists or dental surgery assistants (mean age: 24.3 years) were recruited. Prophylaxis and oral hygiene reinforcement were given 1 x a week for 3 weeks to obtain gingival health and a 3-day period without any plaque control started afterwards. At the end of the 3-day period, the plaque along the gingival margin of the upper right central incisor was removed and direct Gram stained smears were prepared for light microscopy. Bacteria were classified as gram-positive or gram-negative cocci, rods, filaments, fusiform organisms, spirilla or spirochetes. A differential count of 200 organisms from 3-6 microscopic fields was performed and the results expressed as a % of the organisms counted. Results from the 36 direct smears showed approximately 83% (range: 52%-96%) of the organisms to be gram-negative while gram-positive bacteria comprised only a minority of about 12% (range: 0.7%-43%). This result is remarkably different from previous reports from the West where gram-positive bacteria were the predominant bacterial types noted in early supragingival plaque. Further longitudinal studies involving both microscopy and bacteriological culture will be necessary to confirm this finding.