Variability of Two Sampling Methods in Plaque Samples Kuei-ling C. Hsu Noel K Childers, Committee Chair

Introduction: Dental caries remain the most common infectious disease in children, and is in fact, on the rise in the U.S. among 2 to 5 year olds. Among hundreds of oral bacteria, mutans streptococci (MS) are considered the major species associated with dental caries. Studies have shown that increased MS in saliva or plaque is an important indicator for caries. The use of standard plate count (SPC) from plaque samples particularly yield variable quantitative results because of complexities of sample collection and processing. Objective: This study was undertaken to determine collection reproducibility in plaque samples from permanent first molars using two methods of sample collection: a pooled sample and four individual tooth samples. Materials and Methods: Plaque samples were collected from two groups of healthy subjects, one aged 17–50 and the other 6–12 years. Each subject was randomly assigned to either “I” (individual tooth collected-first sampling) or “P” (pooled teeth -first sampling) group. Plaque samples were processed and quantified for total streptococci (TS) and Streptococcus mutans (Sm) using traditional plate culture method. The Sm/TS ratio was used to determine the reproducibility within “P” and “I” group samples. Results: Mean percentage of Sm/TS in pooled and individual sampling methods were 1.64 and 1.21, respectively (not significantly different, p>0.05, ttest). However, for detection of Sm, there was a significant difference between pooled and individual sampling methods (individual-sampling more sensitive, p<0.05, McNemar’s test). Conclusions: Despite the lack of a significant difference between the sampling methods for quantitation of Sm/TS, the difference in Sm detection suggests that individual samples (i.e. more samples collected) are more consistent; however the added resources requiring 4 times the number of samples to be processed might not be justified