Effect of food-simulating liquids on surface characteristics of composite and polyacid-modified composite restoratives.

The chemical environment is one aspect of the oral environment that could have an appreciable influence on the in vivo degradation of composite resins. The effects of food-simulating liquids on the surface roughness and hardness of composite (Silux Plus, Z100, Spectrum TPH, and P50) and polyacid-modified composite resins (F2000 and Dyract AP) were thus investigated and compared. Sixty disks of each material were made. Half were used for microhardness testing and the remaining half for studying surface roughness using profilometry. Each group of 30 disks was subdivided into six groups of five and conditioned for one week as follows--Group 1 (control): air at 37 degrees C; Group 2: distilled water at 37 degrees C; Group 3: 0.02 N citric acid at 37 degrees C; Group 4: 0.02 N lactic acid at 37 degrees C Group 5: heptane at 37 degrees C; Group 6: 50% ethanol-water solution at 37 degrees C. Data were analyzed using one-way ANOVA and Scheffé's test at a significance level of 0.05. Results showed that the surface roughness of all restoratives evaluated was not significantly affected by food-simulating liquids. No significant change in surface hardness was noted with conditioning of Spectrum TPH, Dyract AP, and F2000 in the various food-simulating liquids. The BIS-GMA-based composites Silux Plus, Z100, and P50 appeared to be more susceptible to the softening effects of some food-simulating liquids.