Comparison between different methods for sampling cariogenic microorganisms in persons with exposed root surfaces

The levels of lactobacilli, mutans streptococci and the group of Actinomyces viscosus and Actinomyces naeslundii in a 15-s rinse were compared with the levels of these bacteria in paraffin-stimulated saliva and in pooled plaque from exposed root surfaces. Samples were obtained on 2 occasions from 30 subjects. The levels of lactobacilli, mutans streptococci and Actinomyces spp. in the rinse correlated strongly with the levels in the saliva (r=0.95, r=0.87, r=0.66 respectively). The mean levels of lactobacilli, mutans streptococci and Actinomyces spp. per ml were about 5, 10 and 4 limes higher respectively in the saliva than in the rinse medium. The correlations between the rinse levels and the levels in plaque were O.68, 0.65 and 0.42 but the correlations between saliva and plaque levels were even weaker (0.53, 0.56 and 0.38). The results indicate that a 15-s oral rinse can be as useful as saliva sampling when discriminating between high and low levels of caries-associated microorganisms in root surface plaque. The rinse method has definite advantages compared to saliva sampling in persons with low salivary secretion rate or difficulties to chew.