Effect of the photoactivation mode on microtensile strenght and microhardness

Objectives: This study aimed to evaluated the effect of the composite photoactivation technique on microtensile bond strength and Knoop microhardness. Methods: Standard class I cavities (3x3x4mm) were restored with two adhesives systems, Single Bond (SB) and Clearfil SE Bond (CB), and the TPH composite. The photoactivation of the composite was carried by three techniques: CO (400 mw/cm² x 40s), SS (100 mW/cm² x 10s + 600 mW/cm²x 30s) and PD (100 mW/cm² x 3s + 3m wait + 600 mW/cm² x 37 s). For microtensile test, beams obtained from the buccal wall bond interface were tested under tension at 0.5 mm/min until failure. For the microhardness test, the restoration was sectioned in two halves and on the internal surface of each half, 9 indentations were made. Results: In the microtensile test, SS presented the highest values, with statistical differences for CO. PD presented intermediate values without differing from the others in a significant way. For adhesives, SB presented a higher vaule than CB.In the microhardness test, PD presented highest values, differing significantly from SS. The SS-CB interaction presented the lowest values with statistical diffrences from all the others. Conclusions: By the SS technique, the highest bond strength was obtained. However, this technique made it possible for the adhesive system to intervene in the hardness of composite.