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When using light-induced fluorescence (LF) red plaque fluorescence is sometimes observed. This presumably originates from porphyrins produced by anaerobic bacteria [König K et al.: SPIE 1993;2080:170-180]. To study the relationship between red plaque fluorescence and actual plaque presence we examined 38 first-year dental students and 2 of their teachers for plaque fluorescence. As a control we used D&C Red #28, 1.5% (Butler) which stains all plaque. Images of the buccal surfaces of the 27 and 37 and the lingual surfaces of the 17 and 47 were obtained using an LF camera before and after disclosing plaque. All images were stored on PC for analysis using customised software to distinguish (1) the tooth surface from the background and (2) the red fluorescing area on the surface. When no intrinsic red plaque fluorescence was visible we would find a disclosed plaque coverage varying from 0-96% [mean 24 B 20 (SD)%]. Of 160 surfaces studied, 49 surfaces displayed an intrinsic red plaque fluorescence, with a disclosed plaque coverage between 6 and 82% (mean 42 B 19%). For surfaces displaying red auto-fluorescence, the area of non-disclosed and disclosed plaque correlated (r = 0.76) when a linear relationship through zero was assumed. Red fluorescing plaque was mainly found at the gingival region of total plaque formation which corresponds to the location of initial plaque formation. The disclosed plaque covered an area approximately 55% larger than the area displaying red fluorescence. In conclusion the intrinsic red fluorescence found in plaque is related to the actual area covered with plaque. These findings could be explained by red fluorescence being associated with specific bacteria in mature plaque. |