Effect of rewetting suspensions of bioactive-glass on resin–dentin bond strength

Abstract

Purpose: The aim of this study was to evaluate the effect of bioactive glass suspensions used to rewet dried demineralized dentinon the resultant immediate and3-monthbondstrength of one adhesive system to dentin. Methods and materials: The experimental bioactive glass was prepared by mixing different amounts of oxides (NbO5; (NH4)2HP4; CaO; Na2CO3). The average particle size, distribution and composition of the bioactive glass powder were determined by SEM and EDS. Sixty-five extracted human third molarswere used. Crowns fragmentswere embedded in transparent acrylic resin andpolished onwet #320-grit SiC paper for 20 s before bonding. The specimens were assigned into 5 different groups (n=13). The dentin surface was etched for 20 s with 34% phosphoric acid gel, rinsed with water for 20 s and air-dried with an oil free syringe for 30 s. The surface was then rewetted with either one of the four different concentrations of bioactive Nb/P suspension glasses (5%, 10%, 20%, 40%, w/v), or distilled water (control) brushed for 10 s and two consecutive layers of an adhesive system (One Step, Bisco, USA) were applied to dentin (20 s air-dried/20 cm distance) and polymerized for 10 s/1500mW/cm2. Two cylinders of composite resin were bonded to dentin and light polymerized for 40 s. The bonded samples were stored in a phosphate-calcium buffer solution (PBS) and tested in a shear mode at 0.5mm/min after 24h and 3 months. Failure modes were classified as adhesive, mixed and cohesive (resin). The data were analyzed by 2-way ANOVA and Holm–Sidak tests at a=5%. Results: There were no significant differences among the different concentrations of suspensions for both storage periods (F=0.26; p=0.9) and no significant interactions were observed (F=1.13; p=0.3). Storage time caused significant effects (F=14.1; p<0.001). Significant reductions in bond strength were observed after 3 months PBS storage for the Control and 5% suspension groups. No significant differences were observed for the higher concentrated suspensions. Values are MPa±SD. All groups showed a predominance of adhesive failure mode (Table 1).