Methods: Forty complete or partial removable poly (methyl methacrylate) based dentures from 35 subjects were screened for the presence of red fluorescent plaque deposits under QLF. Dentures were photographed, images were recorded using QLF, and samples of fluorescent plaque were taken. Denture plaque was disclosed and further images were taken. Plaque sample and toothpick in reduced transport fluid were vortexed and the resultant plaque suspension was diluted and spread plated on Fastidious Anaerobe agar and Wilkins Chalgren agar (both containing blood), and Sabouraud Dextrose agar. The blood plates were screened under QLF after 72 h anaerobic incubation and red fluorescing colonies were picked from primary cultures, sub cultured for isolation, and identified by Gram reaction, catalase and oxidase reactions, and API 20A profiles. Identities were confirmed by 16S rRNA sequencing.
Results: Plaque was visible from clinical images before disclosing on 22 of the 40 dentures or 18 of the 35 subjects, and of these 14 of 22 dentures or 11 of 18 subjects had red fluorescent plaque. Red, orange and green fluorescence was detected from plaque on the fitting and non-fitting surfaces of dentures. The red and orange fluorescing species isolated and identified were Prevotella melaninogenica, Actinomyces israelii and Candida albicans, predominantly found in mature plaque. C.albicans was recovered from six of the 11 subjects with red fluorescent plaque. The dentures with red fluorescent plaque had notably more visible plaque coverage and an unpleasant odour was detected from nine of the 14 dentures.
Conclusion: Microorganisms indicative of mature plaque contribute to the red fluorescence observed during QLF analysis. Dentures allow QLF examination of plaque in the absence of interference from enamel, providing a uniform background colour.