Effects of viscosity and surface moisture on bond strengths of resin-modified glass ionomers

Purpose: To evaluate the effects of surface moisture and material viscosity on the shear bond strength of resin-modified glass ionomers to dentin. Materials and Methods: Sixty human teeth were mounted in phenolic rings and ground to obtain flat facial and lingual dentin surfaces. The specimens were assigned to six treatment groups. Three groups were first conditioned with 10% polyacrylic acid. On one surface of each specimen, dentin was left visibly moist prior to application of the restorative material. On the opposite surface the dentin was dried, but not desiccated, after conditioning. For these three groups, Fuji II LC resin-modified glass ionomer was mixed at powder/liquid (P/L) ratios of 1.4, 3.0 and 3.6 and applied to the conditioned dentin in 2.5 mm diameter molds. The other three groups were treated with Vitremer primer. One surface of each specimen was ''dry'' and one surface was ''moist'' before primer application. Vitremer restorative material was mixed at P/L ratios of 2.2, 2.5 and 2.8 and applied to the primed surfaces. Shear bond strengths were measured using a universal testing machine. Data were subjected to three-way ANOVA and Tukey's multiple comparisons test. Results: Mean shear bond strengths of the two materials ranged from 6.9 to 10.4 MPa and varied little regardless of the viscosity of the materials or the degree of surface moistness. The differences among viscosities and surface moistness were not statistically significant. In this in vitro study, the shear bond strengths of two resin-modified glass ionomers were unaffected by the viscosity of the materials and the surface moisture of the dentin substrate.