Effect of Sodium Hypochloride and Chlorhexidine on Dentin Bond Strength

Objective: To evaluate the effect of common dental antiseptic agents on short and long term dentin bond strength. Methods: A total of 180 extracted third molars were divided into 8 experimental groups and 4 control groups, with 15 samples in each group. In four experimental groups 10 % sodium hypochlorite (NaOCl) solution were applied for 60 seconds, and in four other experimental groups 2% chlorhexidine (CHX) solution (Cavity cleanser, Bisco Inc.) were applied for 30 seconds prior to the placement of Excite (EX, Ivoclar North America) or Clearfil SE Bond (CSE, Kuraray Japan) adhesive. Water was used as control. All samples were restored with a hybrid composite (Tetric EvoCeram- Ivoclar) and thermocycled for 500 cycles. The short-term samples were evaluated after 24 hours and the long-term after 9 months. The shear bond strength was tested with an Instron machine. Results: Short term: the mean shear bond strength (Mpa) was 26.96 for CSE-CHX, 22.22 for CSE-NaOCl and 18.08 for CSE-control; and 25.58 for EX-CHX, 23.8 for EX-NaOCl and 15.11 for the EX-control, respectively. The CHX group had statistically significantly higher bond strength values than the control for both adhesive agents (p<0.05). Long term: mean bond strength was 28.36 for CSE-CHX, 19.00 for CSE-NaOCl, and 22.3 for the CSE-control; and 16.3 for EX-CHX, 17.19 for EX-NaOCl and 24.83 for the EX-control, respectively. The NaOCl group had statistically significantly lower bond strength values than the control for both adhesive agents (p<0.05). Long-term bond strength of EX-NaOCl was significantly reduced as compared to short-term (p<0.01). The CHX-CSE group demonstrated significantly higher long term bond strength than CHX-EX (p<0.01). Conclusions: NaOCl is beneficial for the short-term but detrimental to the long-term dentin bonding strength. CHX has beneficial short-term effects, but its long-term effects seemed dependent on the type of adhesives.