The recovery effect of proanthocyanidin on microtensile bond strength to sodium hypochlorite-treated dentine.

OBJECTIVE

To evaluate the recovery effect of proanthocyanidin (PA) on microtensile bond strength (μTBS) to sodium hypochlorite (NaOCl)-treated dentine.

METHODS

Fifty-five freshly extracted third molars with intact dental crowns, no caries or restorations were sectioned to expose a sound middle layer of dentine and were randomly divided into 11 groups. In the blank control group, dentine surfaces were immersed in deionized water for 20 min. In the negative control group, dental surfaces were immersed in 5.25% NaOCl for 20 min. In the other nine experimental groups, after immersion for 20 min in 5.25% NaOCl, followed by PA (5%, 10%, or 15%) treatment for 1, 5 min or 10 min. The NaOCl solution was renewed every 5 min. Then dentine surfaces were bonded using SE bond. Bonded samples were sectioned into dentine-resin sticks (n = 45) for microtensile bond strength testing (MPa). Failure modes were observed and classified into three types with a stereomicroscope. Microtensile bond strength data were analysed using one-way anova. The confidence interval test was performed to analyse the recovery effect of PA on bond strength to NaOCl-treated dentine. The chi-squared test was used to analyse failure mode distribution.

RESULTS

After use of 5.25% NaOCl for 20 min, microtensile bond strength in the negative control group decreased significantly compared with that of the untreated group (P < 0.05). After a recovery treatment of 10% PA for 10 min or 15% PA for more than 5 min, the bond strength was restored to at least 90% of baseline (P < 0.05). No recovery effect on bond strength was detected after the application of 5% PA for 1 min (P > 0.05). Adhesive fracture was found to be the most common failure mode in the NaOCl-treated group. After the recovery application of PA, the proportion of mixed failures increased significantly (P < 0.05).

CONCLUSIONS

Microtensile bond strength to NaOCl-treated dentine recovered after the application of either 5% PA for more than 5 min or 10% or 15% PA for more than 1 min. The application of PA before an adhesive procedure may immediately restore the compromised bond strength of NaOCl-treated dentine.