Effect of Water Line Disinfectants on the Composite Bond

Objectives: Due to potentially high microbial content and biofilm formation, dental unit water systems are required by the American Dental Association to contain no more than 200 colony forming units per milliliter (cfu/mL). This study examined the effect of waterline disinfectant on composite bond strength. Methods: 16-18 samples were tested for each group to determine the shear bond strength of bonded composite to human dentin. Samples of non-carious, non-restored extracted human teeth were mounted in acrylic resin and sectioned with a diamond saw. The exposed tooth surfaces were etched and rinsed and subsequently applied with bonding agent and Esthet-X composite resin per manufacturer's instructions. Each of the three groups of samples were placed in water from one of three sources: the dental school's clinic waterline; distilled, deionized water containing dissolved ICX tablets (A-DEC); and distilled, deioninzed water with no disinfectant, which served as a control group. These samples were tested after 24 hours to allow time for maximum bonding to occur. The shear bond strength of the Esthet-X composite with exposure to different disinfectants was tested using a universal testing machine (Instron 5567, Camden MA). Results: Bond strengths for the waterline samples averaged 12.5 MPa (S.D. 8.66 MPa), while the bond strengths for the ICX samples averaged 15.23 MPa (S.D. 9.3 MPa), and the bond strengths for the deionized/distilled water samples averaged 14.49 MPa (S.D. 10.26 MPa). No statistically significant differences were found between the three groups by an analysis of variance (ANOVA) (F= 1.036; p=0.31). Conclusions: No decrease in bond strength with the use of water line disinfectants is a very beneficial result to clinicians who want to maintain safe practices while providing the best restorative care to their patients. Supported by the UTHSC Dental Alumni Endowment Fund for Research