The Comparative Evaluation of Antibacterial Activity of Methacryloxydodecyl Pyridinium Bromide and Non-methacryloxydodecyl Pyridinium Bromide Dentin Bonding Systems Using Two Different Techniques: An In vitro Study

BACKGROUND Adhesive systems have enabled clinicians to preserve more tooth structure by changing cavity designs. However, because of the polymerization shrinkage adhesive systems are not capable of totally prohibiting the gap formation between the cavity and restorative material of composite resin leading to colonization of oral microorganisms from saliva. One possible solution for this serious problem is to use dental materials with antibacterial properties. So the development of such agents has initiated for successful restorations. Hence, the purpose of this study was to compare the antibacterial activities of two dentin bonding systems: Clearfil protect bond (CPB) and prime & bond NT using agar well technique and tooth cavity model. MATERIALS AND METHODS CPB and prime and bond NT (PBNT) were evaluated in this study using agar well technique and tooth cavity model. In the agar well technique, the materials were filled in the wells of Muller-Hinton agar plates inoculated with Streptococcus mutans NCTC 10449M and the diameter of inhibition zones produced around the materials were measured after 24 h of incubation. For the tooth cavity model test, 3 cavities (of diameter - 1 mm and depth - 2 mm) were prepared in the flat occlusal dentin of human extracted molar. After sterilization, the teeth were left in the culture of broth of S. mutans at 37°C for 72 h for allowing bacteria to invade the cavity for 72 h. The dentin bonding systems were applied separately to each of the two infected cavities, and the third cavity was not applied and used as control. After sealing the occlusal surfaces, the teeth were kept in sterile physiological saline at 37°C for 72 h. The standardized amounts of dentin chips (120 + 5 mg) were obtained from the cavity walls, and the numbers of bacteria recovered were determined. The results were analyzed using one-way ANOVA, Kruskal-Wallis and Mann-Whitney's U-tests. RESULTS The primer of CPB and PBNT produced similar inhibition zones (P > 0.05), but the bonding resin of CPB did not produce any inhibition. When tested by the tooth cavity model technique, the application of CPB resulted in significantly less bacterial recovery than the PBNT (P < 0.05), demonstrating substantial antibacterial effects. CONCLUSION The CPB that employs the antibacterial primer containing methacryloxydodecyl pyridinium bromide, was effective in inactivating the bacteria in the cavity compared to little antibacterial activity shown by PBNT. The tooth cavity mode test used in the present study is a reliable method to evaluate the antibacterial effects of dentin bonding agents simulating clinical situations.