Quantification of root surface plaque using a new 3-D laser scanning method

There are no published reports in the literature objectively quantifying thickness of plaque on teeth. The aim of this study was to quantify plaque on a tooth surface and assess if this quantification correlates with a clinical index of plaque from each of 51 patients. Patients were instructed not to perform any oral hygiene on the day of the assessment. The Silness and Löe plaque index was scored and replicas were scanned using a co-ordinate measuring machine (CMM) and laser scanning probe. A replica was obtained from this surface before and after toothbrushing. Plaque adjacent to the gingival margin had a mean thickness of 0.106+/-0.118 mm (mean+/-SD) whilst mean plaque thickness 250 microm from the gingival margin was 0.053+/-0.052 mm (mean+/-SD). There was a significant correlation between the plaque index and the plaque thickness (p < or = 0.002). The finding that plaque is present in the greatest amount adjacent to the gingival margin supports a previously reported hypothesis that primary root carious lesions (PRCL's) may initiate adjacent to the gingival margin. This method quantifies plaque thickness on exposed root surfaces which correlates with the plaque index as well as illustrating how the morphological characteristics of teeth, gingivae and plaque can be studied in vivo from replicas recorded.