Mutans streptococci in subgingival plaque of treated and untreated patients with periodontitis

Background: The etiology of root caries is thought to be identical to coron al caries, though root caries seem to be more complicated because of the hi gher susceptibility of exposed roots (dentin) by periodontal therapy to dem ineralization than intact enamel. This implies that mutans streptococci are the most likely pathogens in the development of root caries. Although it i s known that both the numbers of mutans streptococci and the frequency of i solation in root caries lesions are negatively correlated with the distance from the gingival margin, the subgingival sulcus has not been considered a possible habitat for mutans streptococci. However, subgingival occurence o f mutans streptococci in both untreated and treated periodontal patients ha s not been documented well in the literature. Objective: To investigate the presence and levels of mutans streptococci in the subgingival plaque of patients (n=154) in different stages of periodon tal therapy. The subgingival sulcus may be a possible habitat for mutans st reptococci. This localisation of mutans streptococci may be of importance i n the development of root caries after periodontal surgery. Materials and methods: In this cross-sectional study, subgingival plaque sa mples from 154 consecutive adult periodontitis patients were tested for pre sence and levels of mutans streptococci and putative periodontal pathogens by anaerobic cultures. These patients were divided into 3 groups based on t heir stage of periodontal treatment: (1) untreated patients; (2) patients a fter initial periodontal therapy only; (3) patients in the maintenance phas e who not underwent periodontal surgery; (4) patients after periodontal sur gery. Results: The prevalence of mutans streptococci in the 4 study groups varied from 82% in untreated patients to 94% in maintenance patients. The mean pr oportion of mutans streptococci was 6.65% in maintenance patients versus 1. 86% in untreated patients (p=0.005) and 2.51% in patients after scaling and root planing (p=0.041). Conclusions: The subgingival area is a microbial habitat for mutans strepto cocci that may be of importance in the development of root caries in period ontitis patients.