Barcoll hardness of dental materials treated with an APF foam.

The hardness of a dental material is generally related to its mechanical properties. The purpose of this study was to evaluate the hardness of several resins and cements exposed to an APF Foam (Minute Foam, Oral-B). Four molds 6 x 2 mm were prepared for each experimental condition with each of the following materials: Filtek P 60 (3 M); Silux Plus (3 M); Ariston pHc (Vivadent); F 2000 (3 M); Vitremer Restorative (3 M) and lonofil Molar (Voco). Immediately after prepared, the samples were stored in water or in the APF foam. To evaluate the Barcoll hardness, measurements were made on both sides of the specimens (top--T and bottom--B), immediately, and after 1 min, 24 h and 7 d. The results, expressed as percentages of the loss of hardness of each sample from the baseline readings, were analyzed with an ANOVA and Tukey's test. ANOVA revealed the significant influence of material, time and treatment. The surface analyzed (T or B) had no significance. Among the glass-ionomers tested the loss of hardness was significantly higher (+30%) than for resin-based composites (+/- 15%). Treatment with the APF foam for 7 days produced the greatest loss of hardness (42%) and at 24 h the least (less than 5%). There were no other significant findings. It can be concluded that the effect of the APF foam is material dependent, but is significantly more pronounced with the glass-ionomers than the resins tested. The application time of the foam is the main factor for the loss of hardness.