Effects of four different surface treatment methods on the Streptococcus mutans adhesion to dental porcelain

Adhesion of S. mutans to the dental porcelain surface is may lead to development of gingival inflammation and secondary caries. Surface roughness is considered to be a factor affecting the bacterial adhesion to the porcelain. The purpose of this study was to evaluate the effect of four different surface treatment methods on the adhesion of S. mutans to dental porcelains. Sixty specimens (10×3 mm) of Noritake porcelain were fabricated. Specimens were divided into 4 groups (n=15) that were treated with one of the following four surface finishing techniques: 1. glazing 2. overglazing 3. polishing (with Kenda kit) 4. nonglazed (without any surface treatment). The samples were exposed to bacterial suspension (1x106 cell/ml) with standard code of S. mutans PTCC1643، and were cultured in blood agar. The level of adhesion of the S. mutans on specimens was assessed and the specimen’s surface roughness were determined with SEM. Data was analyzed with one-way Kruskal-Wallis and Mann-whitney test and the correlation between the level of adhesion and specimens surface roughness was evaluated by pearson test. The average bacterial adhesion in each group was as follows: Glazed group (35±20. 92)، Overglazed group (28±6. 73)، Polished group (103±22. 1)، Nonglazed group (115±16. 2). There difference in 4 groups was statistically significant (p<0. 05). The average surface roughness in each group was found to be as follows: Glazed group (0. 67±0. 004)، Overglazed group (0. 48±0. 003)، Nonglazed (0. 89±0. 005)، and Polished (1. 7±0. 004). Statistically significant differences were seen between all groups. (p<0. 0001) There was a positive correlation between the adhesion of S. mutans and surface roughness. (p=0. 0001) This in vitro study indicates that the samples in the Overglazed group had the lowest bacterial adhesion whereas the Nonglazed group had the maximum bacterial adhesion. Furthermore، the Glazed surfaces show less adhesion than the Polished surfaces.