Characteristics of Interproximal Plaque of Human Posterior Teeth

Objective: To develop more quantitative and reproducible methods than visual plaque indices to detect changes in quantity and bacterial composition of interproximal plaque of human posterior teeth.

Methods: Six periodontally normal subjects (age 25-47 years) with a mean gingival index score of 0.56 (0.19) were enrolled. Plaque was measured on posterior teeth using the Turesky modified Quigley & Hein Plaque Index (PI). Subjects used a manual brush only. Posterior interproximal plaque was sampled using dental floss on three occasions, each separated by two weeks. One portion per sample was used to determine total bacterial load using a universal oligonucleotide probe and presence and quantity of 7 selected bacteria (P. gingivalis, T. forsythia, T. denticola, F. nucleatum, P. intermedia, E. corrodens, C. rectus) using species-specific oligonucleotide probes. The other sample portion was analyzed for 40 bacterial species using the checkerboard assay system of Socransky.

Results: and Conclusions: Total plaque determined by the sum of the values for the 7 species-specific probes and by the F. nucleatum probe alone showed a high degree of correlation with total plaque measured by the universal probe. Correlation of these values with those from the checkerboard assay were poor. Oligonucleotide probes to measure total plaque provides greater discrimination among subjects and sites than PI. F. nucleatum and E. corrodens were present in almost all samples from all subjects and accounted for more of the total sample DNA than all of the other species combined. Total interproximal plaque quantity and the overall pattern of species composition was consistent from visit to visit per subject, but varied greatly from subject to subject. With an incidence of red complex bacteria of about 75% to 85%, their colonization was far more frequent than expected for periodontally healthy subjects.

Supported by Philips Oral Healthcare