Bond Strength of Different Resin Composites to Various Resin-Based Lining Materials

Abstract

The results of this study demonstrated that bond strength between lining materials and the overlaying restorative ones did not reach the cohesive strength of all tested materials (ranging from 29.5% up to 80.0%), in spite of, all lining materials were light cured in air to simulate what was happened in the clinical situations. The effect of the presence or absence of the oxygen-inhibition layer on bond strength between layers of resin composite [112, 127] or in the immediate repair composite-to-composite bond strength [128, 129] showed controversial data. The lower bond strength between lining materials and overlying restorative ones compared to the cohesive strength might be explained by; the photoinitiator in the oxygen inhibition layer was consumed and decomposed during the first attempt of light curing. In addition, the short half-life of compherquinone was observed by increasing the intensity of the light curing up to 500mW/cm2 and 50% of the compherquinone was decomposed after 23 second light curing time with 500mW/cm2 light intensity [130]. In the present study, the top surfaces of the lining materials were light cured for 20 seconds with intensity of 1200mW/cm2. The high intensity provided by the light curing unit might consume and decompose the photoinitiators on the oxygen inhibition layer, thus shortening its half-life. This might lead to decrease the bond strength between the lining materials and the overlying restorative ones compared to the cohesive strength of the material themselves.