Shear bond strength of dual-cured resin cements on zirconia: The light-blocking effect of a zirconia crown

Abstract

The presence of restorative material between resin cement and the light-curing unit can reduce light transmission. This study aimed to evaluate the effect of the light-blocking effect of zirconia crown on shear bond strength (SBS) between three dual-cured resin cements and the zirconia surface. Sixty zirconia specimens were prepared and divided into three groups according to the type of resin cement [RXU (RelyX Ultimate); SC2 (SmartCem2); MEC (Maxcem Elite Chroma)]. Each group was further divided into two subgroups, with or without a 1-mm-thick zirconia crown (n=10). The specimens were light-cured from five different directions for 20s each. All specimens were thermocycled 5000 times and subjected to SBS testing, followed by scanning electron microscope examination. The presence of a 1-mm-thick zirconia crown had no significant effect on the SBS in all resin cements. However, the SBS was significantly affected by type of resin cement. RXU showed the highest SBS (8.35MPa with crown; 8.57MPa without crown), followed by SC2 (5.48MPa with crown; 5.57 without crown) and then MEC (3.37MPa with crown; 4.04MPa without crown. Fractured surfaces exhibited varying degrees of mixed failure patterns. A 1-mm-thick zirconia crown material between the light source and the dual-cured resin cement did not significantly influence the SBS of the resin cements on the zirconia substrates. RXU exhibited the highest SBS regardless of zirconia crown coverage. With sufficient light-curing, dual-cured resin cements can be a good choice for zirconia crown cementation.