Microbial screening of Cariostat ® -inoculated plaque samples from low and high caries risk children

Abstract

The aim of the present study was to investigate caries activity and it's association with the presence of S. mutans and S. sobrinus. The subjects were 499 children aged 2.5 years old, who participated in dental health examinations held from May 2006 to January 2007 at a health center in Katano City, Osaka, Japan. A dental examination was performed based on caries diagnostic criteria of the Health Policy Bureau, Ministry of Welfare, Japan. Plaque samples were collected using a sterile cotton swab from the maxillary buccocervical surfaces by the same dental hygienist. Two hundred seventy two (54.5%) children who had Cariostat score below 1.5 were determined as low risk and 227 (45.5%) who had a score above 2.0 as high risk. For microbial screening, 100 children were randomly selected from the high and low risk groups. The presence of S. mutans and S. sobrinus were detected using PCR technique. Thirty seven (18.5%) children had S. mutans alone, 20 (10.0%) had S. sobrinus alone, 16 (8.0%) had both S. mutans and S. sobrinus, and 127 (63.5%) had neither S. mutans nor S. sobrinus. Cariogenic bacteria were detected more from high caries risk than low caries risk children. A larger number of S. sobrinus was found in children with high df numbers than low df numbers. In this study, it was shown that S. sobrinus was more closely related with high caries risk activity and high df numbers. oral microorganisms that have virulence factors related to cariogenicity 7,8). These bacteria are acidogenic, aciduric and produce specific intra-and extrapolysaccharides that facilitate microbial adherence on teeth 8,9-12). Their amount and virulence, together with the patient's age at which these bacteria were contracted, are important factors in determining the course of this disease 3,13-15). Therefore, the levels of Mutans streptococci are considered to be important indicators for assessment of caries risk or management of caries prevention 7,16). The genetic diversity of these cariogenic bacteria is still controversial 18) , some suggesting that S. mutans has been shown to be more prevalent 1,19,20) and others found that S. sobrinus is more closely related with high caries activity and seldom found without S. mutans 18,21,22). Furthermore, Kozai et al. 23) and Klien