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

Abstract

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.

Recent Advances in Adhesive Bonding: The Role of Biomolecules, Nanocompounds, and Bonding Strategies in Enhancing Resin Bonding to Dental Substrates

“…In addition, EDC has very low cytotoxicity (19), showing great biocompatibility than other crosslinkers. Usually, carbodiimide has been applied to dentin after acid-etching, resulting in strengthening the hybrid layer due to the formation of stable covalent bonds with collagen fibrils (23). Some studies have also shown that EDC possesses protease inhibition properties (24, 25), although at present, it is difficult to ascertain whether collagen crosslinking ability or the protease inhibition properties of EDC play an equally important role or whether one factor predominates over the other in increasing resin-dentin bond durability (26).…”

“…Proanthocyanidins are natural crosslinkers derived from polyphenols, which are able to enhance the mechanical properties of dentin, thus improving the quality of the hybrid layer (23, 27, 28). The incorporation of proanthocyanidin to an experimental adhesive did not show adverse effects on the immediate resin-dentin bond strength when its concentration was less than or equal to 2% (29).…”

“…Riboflavin 5-phosphate is a crosslinker that produces free radicals through photo-oxidation (UVA), resulting in improved collagen matrix stiffness and effective adhesive resin penetration (23). Bromelain enzyme acts by removing unsupported collagen fibrils of acid- etched dentin and by improving the surface energy of dentin, thus enhancing resin infiltration and hybrid layer formation (34).…”

“…A few recent studies have also suggested that, by modifying the bonding protocol of adhesive systems, significant gains in the immediate and/or long-term resin-dentin bonds may be obtained (23, 50, 94–98). The most cited approach was the application of a hydrophobic resin after bonding steps, followed by an air blower to achieve an optimally thin adhesive layer (95, 97, 98).…”

“…The second approach identified with the present review was the ethanol-wet bonding (EWB) technique, which has been the purpose of investigation for several studies; however, only two studies (23, 50) were included, according to our literature search criteria. One of the studies tested the effects of the EWB technique on coronal dentin (23).…”