Effect of reducing agents on bond strength to NaOCl-treated dentin

Objective

The purpose of this study was to evaluate the effect of three antioxidant/reducing agents with different application times on microtensile bond strengths to sodium hypochlorite-treated dentin.

Methods

The occlusal surfaces of 24 extracted human third molars were horizontally cut to expose sound dentin. The teeth were divided into eight groups. The dentin surfaces of the teeth were treated as follows: group 1, no treatment; group 2, treated with 6% sodium hypochlorite (NaOCl) for 30 s; groups 3-8, applications of 10% sodium ascorbate solution, 100 μM rosmarinic acid solution or Accel for 5 or 10 s after the same treatment as in group 2. All treated dentin surfaces were bonded with a 2-step self-etching adhesive system (Clearfil Protect Bond) and restored with a resin composite (Clearfil AP-X). After storage in water for 24 h, the bonded specimens were subjected to the microtensile bond test at a crosshead speed of 1.0 mm/min. Data were analyzed by a one-way ANOVA and Tukey test (p < 0.05).

Results

The NaOCl-treated group had significantly lower bond strength than the control group (p < 0.05). The application of sodium ascorbate solution for 5 or 10 s did not significantly increase the compromised bonding to NaOCl-treated dentin (p > 0.05). On the other hand, Accel and rosmarinic acid solution had significant reversal effects with the same application times (p < 0.05).

Significance

The reversal effect on compromised bonding to NaOCl-treated dentin depended upon the type of antioxidant within the short application time. Applying Accel or rosmarinic acid for 5 or 10 s improved bond strengths to NaOCl-treated dentin.