Microbiological impressions of teeth, saliva and dietary fibre can predict caries activity

Objectives Mutans streptococci and Lactobacilli on impressions of teeth and caries tests were used to identify caries prone subjects. Methods Twenty-seven dental students were examined for caries initially and after 4 years. At the initial examination plaque index; saliva flow, buffering capacity and lysozyme; sucrose and fibre consumption; Lactobacilli and mutans streptococci in saliva and on alginate impressions were measured. Data was analysed using Kruskal–Wallis, Wilcoxon–Mann–Whitney and Spearmanʹs Rank correlation tests and linear discriminant analysis. Results The best predictor of caries increment was decay. Nine subjects had no caries or restored teeth with caries (Group A); 9 had restored teeth with no caries but developed an average of 8 new decayed surfaces (Group B); 9 had an average of 4.4 decayed surfaces and developed a further 9.6 (Group C). Group A had fewer filled surfaces than Group B (p = 0.02) and Group C (p = 0.024) a higher flow rate of stimulated saliva than Group B (p = 0.02) and Group C (p = 0.012). Microorganisms were cultured from all decayed teeth, 98% that developed decay, 89% filled and 69% sound teeth. Fibre intake, saliva flow and the percentage of teeth or sound teeth with Lactobacilli and mutans streptococci gave a specificity of 89%, a sensitivity of 100% and predicted an increase in decay in all Group B subjects while one subject from Group A was misclassified. When teeth with microorganisms were excluded four subjects were misclassified. Conclusions Growth of cariogenic microorganisms on alginate impressions, saliva flow and dietary fibre predicted caries activity in most subjects.