Browsing School, Graduate by Author "Vo, Diane"
Streptococcus mutans Bacterial Adherence on Lithium Disilicate Porcelain SpecimensVo, Diane; Masri, Radi, 1975-; Jabra-Rizk, Mary Ann (2015)Streptococcus mutans as it pertains to dental and oral health is significant for its role as the primary etiologic factor of caries. While primary caries results from initiation of lesions in virgin tooth structure, secondary caries is a significant contributing factor to the replacement of dental restorations. Caries formation is directly related to plaque accumulation, which is mediated by bacteria adhesion to intraoral surfaces. In the case of the restored tooth, bacteria must adhere to the restorative material, particularly along margins in order to cause recurrent pathology. A material that has recently come into much favor is lithium disilicate, a glass based system with fillers in a homogenous glass. Lithium disilicate restorations can be either (1) pressed or (2) milled to fabricate inlays, onlays, veneers or single unit crowns. These restorations can be full-contour, or may be cut back and subsequently modified with (3) veneering fluorapatite, or (4) glazed. With respect to bacterial adhesion to restorative surfaces, the overwhelming factor is surface roughness. The threshold for this effect has previously been found to be 0.2 µm Ra value, above which there was a positive correlation between surface roughness and plaque retention. Specimens were fabricated for each of the four preparation types per manufacturer's recommendations and incubated with S. mutans UA159 wild-type. Biofilms adherent to specimens were then sonicated, redispersed, and plated for quantification. Results were tested with an analysis of variance (ANOVA). Significant differences that were found were further analyzed by Tukey's Honestly Significant Difference (HSD) test. Pearson's r was also be used to evaluate the relationship between surface roughness and biofilm accumulation. A p-value of ≤ 0.05 was considered significant. Surface roughness, as quantified by Ra values, indicated that Press and CAD groups were not significantly different from one another, but were significantly lower than that of ZirPress/Ceram, which was lower than surface roughness of the Ceram Glaze group (F = 513.898, p ≤ 0.0005). Similarly, CFUs/ml for the CAD and Press groups were significantly lower than the ZirPress/Ceram group, which were also significantly lower than those of the Ceram Glaze group (F = 201.721, p ≤ 0.0005). A strong positive association was also seen between surface roughness and biofilm accumulation (r = .95). Many factors, such as caries risk, presence of other restorations, and individual patient hygiene, influence whether these differences in surface roughness and biofilm accumulation become clinically relevant to the formation of caries. The present study has demonstrated that different preparations vary in their surface roughness and biofilm accumulation measurements, and that these differences in surface quality are associated with bacterial adherence.