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 Spearman's 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.