Resin bond strength to water versus ethanol-saturated human dentin pretreated with three different cross-linking agents

CONTEXT: Resin-dentin bonds are unstable owing to hydrolytic and enzymatic degradation. Several approaches such as collagen cross-linking and ethanol-wet bonding (EWB) have been developed to overcome this problem. Collagen cross-linking improves the intrinsic properties of the collagen matrix. However, it leaves a water-rich collagen matrix with incomplete resin infiltration making it susceptible to fatigue degradation. Since EWB is expected to overcome the drawbacks of water-wet bonding (WWB), a combination of collagen cross-linking with EWB was tested. AIM: The aim of this study was to compare the effect of pretreatment with different cross-linking agents such as ultraviolet A (UVA)-activated 0.1% riboflavin, 1 M carbodiimide, and 6.5 wt% proanthocyanidin on the immediate and long-term bond strengths of an etch and rinse adhesive system to water- versus ethanol-saturated dentin within clinically relevant application time periods. SETTINGS AND DESIGN: Long-term in vitro study evaluating the microtensile bond strength of adhesive-dentin interface after different surface pretreatments. SUBJECTS AND METHODS: Eighty freshly extracted human molars were prepared to expose dentin, etched with 37% phosphoric acid for 15 s rinsed, and grouped randomly. They were blot-dried and pretreated with different cross-linkers: 0.1% riboflavin for 2 min followed by UVA activation for 2 min; 1 M carbodiimide for 2 min; 6.5 wt% proanthocyanidin for 2 min and rinsed. They were then bonded with Adper Single Bond Adhesive (3M ESPE), by either WWB or EWB, followed by resin composite build-ups (Filtek Z350, 3M ESPE). Bonded specimens in each group were then sectioned and divided into two halves. Microtensile bond strength was tested in one half after 24 h and the other after 6 months storage in artificial saliva. STATISTICAL ANALYSIS USED: Analysis was done using SPSS version 18 software (SPSS Inc., Chicago, IL, USA). Intergroup comparison of bond strength was done using ANOVA with post hoc Tukey's test, and intragroup comparison was done using paired t-test. RESULTS: The microtensile bond strength of cross-linked groups was higher compared to control group (P < 0.001). EWB showed much higher bond strength values on cross-linked dentin compared to noncross-linked dentin. UVA-activated riboflavin group exhibited highest bond strengths followed by carbodiimide and proanthocyanidin groups, respectively, on both water- as well as ethanol-saturated dentin. Even after 6 months storage, cross-linked groups showed significantly higher values compared to initial bond strength values of control group (P < 0.001). CONCLUSIONS: 0.1% riboflavin pretreatment of dentin followed by UVA activation for 2 min exhibited highest increase in bond strength values at 24 h and least reduction in bond strength values after 6 months storage compared to other groups. Biomodification of dentin using collagen cross-linking followed by EWB exhibited a synergistic effect in improving the resin-dentin bond durability.