FACTORS INFLUENCING SHEAR-STRENGTH OF INCREMENTALLY CURED COMPOSITE RESINS

Factors influencing the shear strength of incremental curing of three different composite resins were examined. The first increment was cure d under different surface conditions, in air, or under a coverglass. A separate experiment studied the effect of curing in nitrogen atmosphe re. There was no difference in the shear strength of the specimens if the first increment was created in air or under a coverglass. One mate rial (Heliomolar RO) showed higher shear strength when cured in increm ents and one when bulk-cured (Herculite XR). Curing increments in a ni trogen atmosphere increased the shear strength for two of the three ma terials tested (P50 and Heliomolar). The results showed that the bond strength between the increments of composites was influenced by the su rface properties of the composites themselves after they had been cure d under the different conditions; it was also affected by the inherent chemical and physical properties of the materials utilized.