Evaluation of shear bond strength of universal resin cements to dentin subjected to air-particle abrasion before and after thermocycling: An in- vitro study

PURPOSE: This in-vitro study aimed to evaluate the shear bond strength of two types of universal resin cements to dentin when treated with air-particle abrasion before and after thermocycling. MATERIALS AND METHODS: The human teeth with exposed dentin (n=72) were prepared. All of these samples were then polished with silicone carbide paper. The samples were equally and randomly divided into two groups one of which the dentin bonding surface was pretreated with air-borne particle abrasion (Al2O3, 50µm) (APA group) (n=36) and a control group which did not receive any pretreatment (No APA). Each group (APA, No APA) was further randomly divided into two groups (no=18) according to the cement to be applied, namely: RelyX Universal (3M™ ESPE, St. Paul, MN, USA) and G-CEM ONE Universal (GC, Tokyo, Japan). Bonding procedures were performed in a no-primer, self-etch, self-adhesive mode. According to the period of storage, each group was further divided into two subgroups (n=9); short period of 24-hours in a 37C° water and thermocycling (10000 cycles). Ultimately, all samples were subjected to shear bond strength tests. Failure forms were assessed. The data were analyzed using one-way and two-way ANOVA and Tukey HSD test with a p<0.05 significance level. RESULTS: There was a statistically significant difference in bond strength between samples with and without APA (p<0.05). There was also a statistically significant difference between the mean values of the two cements (p<0.05), and between samples exposed to thermocycling (p<0.05) as opposed to the samples that were not. The group with the highest shear bond values was (RelyX Universal, No aging, APA) (6.26±1.22 MPa), the lowest shear bond values were observed in (G-CEM ONE, Aged, No APA) group (2.75±0.76 MPa). Regardless of the type of the pretreatment and the brand of the cement, the shear bond strength values of most groups were negatively affected by thermocycling (p<0.05). The most occurred mode of failure was adhesive failure (65.3%), however mixed failure was 25% and the least occurred failure was cohesive (9.7%). CONCLUSION: Air-particle abrasion improved the mean values of the shear bond strength. Thermocycling decreased the shear bond strength of most groups. RelyX Universal cement had a higher shear bond strength than G-CEM ONE cement. KEYWORDS: Universal resin cement, Air-particle abrasion, shear bond strength, thermocycling.