Reliability Assessment of Saliva-based Cariogenic Bacteria Counts by Commercially Available Caries Risk Tests in Adult Human Subjects

Purpose: This study compared the reliability levels of the saliva-based bacterial counts assessed by commercially available caries risk tests, Dentocult® and CRT® systems. Methods: Thirty-five healthy adult subjects (mean age 24.8±1.98, mean DMFT 9.4±4.6) were selected from the sixth-grade students (70 students in total) in Okayama University Dental School. At an interval of 10 minutes, stimulated saliva samples were taken twice and incubated to evaluate salivary Streptococcus mutans (SM) and Lactobacilli (LB) counts in each system. Salivary bacterial counts were scored into four classes by five calibrated examiners with the aid of an estimation guide for each system. Based on these scores, the intra- and inter-examiner reliability levels were estimated by using a weighted kappa index. Results: Mean kappa indexes for intra-examiner reliability were 0.71, 0. 80, 0.86 and 0.54 (Dentocult SM, CRT®SM, Dentocult® LB and CRT® LB, respectively) and mean kappa indexes for interexaminer reliabilities were 0.57, 0.75, 0.72 and 0.44 (Dentocult® SM, CRT® SM, Dentocult® LB and CRT® LB, respectively). After data reduction selecting a median value among the five examiner estimates, kappa indexes for the reliability of each microbial assessment were calculated as 0.51, 0.92, 0.83 and 0.79 (Dentocult® SM, Dentocult® LB, CRT® SM and CRT® LB, respectively). Conclusions: These results suggested that both systems had sufficient reliability for assessment of salivary bacterial counts in adult human subjects. Even with a simpler incubation schedule, the CRT® system has the same level of clinically acceptable reliability as the Dentocult® system.