Quantitative analysis of changes in salivary mutans streptococci levels after orthodontic treatment

Abstract

Objectives: This study was designed to analyze the initial changes in salivary Streptococcus mutans, Streptococcus sobrinus levels after orthodontic treatment with fixed appliances. Methods: The subjects consisted of 58 adult patients. Unstimulated whole saliva and simplified oral hygiene index (OHI-S) were obtained at the following 4 time points: at the time of debonding (T1), 1 week after debonding (T2), 5 weeks after debonding (T3), and 13 weeks after debonding (T4). Repeated measures ANOVA was used to determine time-related differences in salivary bacterial levels and OHI-S among 4 time points after quantifying salivary levels of S. mutans, S. sobrinus, and total bacteria using real-time polymerase chain reaction. Results: OHI-S and total bacteria significantly decreased, but salivary mutans streptococci (MS) levels significantly increased after orthodontic treatment. The amount of total bacteria in saliva significantly decreased at T3 (T1, T2 > T3, T4) and OHI-S decreased at T2 (T1 > T2, T3, T4). However, salivary S. mutans and S. sobrinus significantly increased at T3 and T4, respectively (T1, T2 < T3 < T4). Furthermore, the proportion of MS to total bacteria significantly increased at T4 (T1, T2, T3 < T4). Conclusions: This study suggests that careful hygienic procedures are needed to reduce the risk for dental caries after orthodontic treatment, despite overall improved oral hygiene status.