Effect of conditioning times on resin-modified glass-ionomer bonding

To evaluate in vitro the effect of different polyacrylic acid conditioning times on the shear bond strength of a resin-modified glass-ionomer bonded either to enamel to dentin surfaces.

36 flat enamel and 36 dentin bond sites were prepared to 600 grit on human incisors. Five groups (n = 6 per group) for each substrate (enamel or dentin) were conditioned using 20% polyacrylic acid and 3% aluminum chloride for either 10, 20, 40, 80, or 160 s before bonding with the resin-modified glass-ionomer. A non-conditioning group per substrate group was used as a control. A hybrid composite was placed in two increments in a 3 mm diameter matrix on the treated surfaces. The specimens were stored for 4 weeks in distilled water at 37 degrees C. Shear bond strengths were determined using an Instron testing machine with a load rate of 0.5 mm/min. Additionally, 15 enamel and 15 dentin samples were tested with a profilometer to quantify changes in surface roughness during the different conditioning times.

Dentin shear bond strength values were not significantly different among the different groups, including the unconditioned control group. For enamel, the unconditioned group was significantly weaker than any of the conditioned groups. No significant differences (P > 0.05) were found among the conditioned enamel specimens. No significant differences in surface roughness were found for either enamel or dentin.