Methods: Different amounts of 20 % chlorhexidine digluconate were added directly to the primer of Clearfil SE Bond to prepare mixtures of 4 different concentrations of chlorhexidine: 0.05 %, 0.1 %, 0.5 % and 1.0 %. Sixteen extracted third molars were randomly divided into 4 groups. Each group corresponded to 1 of the 4 chlorhexidine concentrations. Each of the 16 teeth was sectioned into 2 halves. One half was customarily bonded with Clearfil SE Bond without chlorhexidine, and the other half was bonded with Clearfil SE Bond containing different concentrations of chlorhexidine. Specimens were stored in 0.9% NaCl containing 0.02% sodium azide at 37°C. Microtensile bond strengths were tested immediately after specimen preparation or 12 months later. The modes of fractures were examined under a stereomicroscope.
Results: Twelve-month storage resulted in significant bond strength reduction of all control groups (p <0.05). When incorporated in Clearfil SE Bond primer, chorhexidine preserved dentin bond in the 0.1%, 0.5% and 1.0% chorhexidine group (p < 0.05); In the 0.05% group, there is no statistical difference of bond strength between control group and experimental group tested at the 12-month period (p > 0.05).
Conclusions: When incorporated in the primer of Clearfil SE Bond, chorhexidine can preserve dentin bond as long as the concentration of chlorhexidine in the primer is higher than or equal to 0.1 %.