Effect of denture base materials on mRNA expression of the adhesion-associated genes from the Streptococcus mutans biofilms.

Dental caries is one of the most important reasons for the failure of removable partial denture. The adhesion-associated genes of Streptococcus mutans, such as gtfBCD, ftf and gbpB, might play an important role in bacterial adhesion to denture base materials. Therefore, the aim of this study was to investigate the influence of denture base materials (heat-curing acrylic resins, cobalt-chromium alloy and ceramics served as control) on the formation of S. mutans biofilms and the mRNA expression of adhesion-associated genes. The viability of the bacteria in biofilms was determined by colony-forming units at 24 and 72 h, meanwhile one sample of each group was prepared for scanning electron microscope (SEM) at 24 h. A real-time reverse transcription polymerase chain-reaction was used to quantify the mRNA expression levels of gtfBCD, ftf and gbpB genes in the presence of various materials. The results revealed that acrylic resins had more S. mutans adhesion than Co-Cr alloy and ceramics in terms of the bacterial viability and SEM observation. The level of gtfBCD expression was the highest in ceramics group and the lowest in acrylic resins group in 24 h biofilms; however, acrylic resins had more gtfBC transcription significantly than other materials at 72 h (P < 0.05). Ftf and gbpB were upregulated in 24 h biofilms on denture base materials compared with control (P < 0.05). These results suggested that the expression profiles of gtfBCD, ftf and gbpB were material-dependent and the physico-chemical properties of the materials might influence the transcription of these genes. Acrylic resins, which had the most bacterial adhesion, might affect biofilm formation via increased expression of ftf and gbpB at 24 h and gtfBC at 72 h.