Diphenyliodonium effect on cements hardness submitted to different activation modes

Objective: The aim of this study was to evaluate the addition of diphenyliodonium hexafluorophosphate (DPI) in resinous cements hardness. Methods: Experimental cements were fabricated from a mixture of Bis-GMA and TEGDMA (1:1 mol%) with different DPI concentrations: 0 (control); 0.25; 0.5; 1 or 2 mol%. Glass fillers previous silanized were added to the organic matrix (60%wt.). The cement was inserted in a steel matrix (4.5mm in diameter x 1mm in thickness), covered with a polyester strip and photopolymerized with a LED light cure unit (BluePhase - IvoclarVivadent) with the continuous high intensity mode  (1200mW/cm², 10s) directly or through a ceramic disc of Empress Esthetic (A3, 10 mm in diameter and 0.7, 1.4 or 2mm in thickness). Knoop microhardness was measured on bottom and top of the samples (n=5) immediately and 24h after photoactivation. Five indentations were done on each face of the sample and the averages were registed. Data were submitted to ANOVA and Tukey tests. Results: All the results are in table 1. In general, hardness increased with the increase of DPI in the cement (p<0.05), except for the cements with 1 and 2 mol% (p>0.05). The hardness values decreased according to the increase of ceramic thickness. For cements with 0.25 and 0.5 mol% of DFI, the hardness was higher on the top of the samples than on the bottom (p<0.05). All experimental conditions showed that immediate values were lower than the hardness measured after 24 hours (p<0.05). Conclusion: DPI optimized the hardness of the resinous cements tested, but there was no difference between the cementes with 1 and 2 mol%. Lower hardness was observed by increasing the thickness of the ceramic. (FAPESP - 2007/06149).