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Comparison of antibacterial activity of simplified adhesive systems
Satoshi Imazato1, Akiko Kuramoto, Tomoyuki Kaneko
1Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Yamadaoka, Suita, Osaka, Japan. imazato@dent.osaka-u.ac.jp
Purpose:
To determine and compare the intrinsic antibacterial activity of commercially available simplified adhesive systems.
Materials And Methods:
The antibacterial activity of five self-etching/priming one-step adhesives and three priming/bonding adhesives against Streptococcus mutans, Lactobacillus casei, and Actinomyces viscosus was assessed by the agar disc-diffusion test and determination of the minimum inhibitory/bactericidal concentration (MIC/MBC). Twenty microl of each adhesive was impregnated into a paper disc and placed on an agar plate inoculated with a bacterial suspension, with or without light-irradiation. The size of inhibition zones produced around the specimens was measured after 48 hours of incubation. The MIC values were measured by serial microdilution assays, visually examining the growth of bacteria after incubation with each adhesive for 24-48 hours. The subcultures were made on BHI agar plates from the wells showing no visible growth of bacteria, and the MBC values were determined based on production of colonies. Two primers in two-step self-etching systems and an experimental primer containing chlorhexidine were tested for reference. The results of disc-diffusion tests were analyzed by ANOVA and Fisher's PLSD test.
Results:
The size of inhibition zones produced by adhesives varied among the brands. None of the available commercial adhesives showed significant inhibition against all three of the bacterial species tested. Light-irradiation reduced the size of inhibition zones for a few materials, but a similar trend to the effectiveness of non-irradiated specimens was observed. The antibacterial activity of commercial products determined in terms of MIC/MBC values were different from the results by disc-diffusion tests. The self-etching adhesives with low pH were not necessarily more effective than priming/bonding solutions, and no significant relationships between the acidity and antibacterial effects were found. Compared with commercial products, an experimental primer containing chlorhexidine produced significantly larger inhibition zones against all species (P < 0.05) and exhibited greater bacteriostatic/bactericidal activity, demonstrating lower MIC/MBC values.