THE INFLUENCE OF DIFFERENT SURFACE TREATMENTS ON MICRO-SHEAR BOND STRENGTH OF TWO RESIN LUTING AGENTS TO MONOLITHIC ZIRCONIA

Purpose. Establishing a reliable bond to zirconia-based materials has proven to be difficult which is the major limitation against fabricating adhesive zirconia restorations. The purpose of this study was to evaluate the micro-shear bond strength of 2 dual-cured adhesive cements to monolithic zirconium oxide ceramic after different surface conditioning treatments.
Material and methods Eighteen 14 × 14 × 1 mm monolithic zirconia ceramic plates were sliced from their respective block by using a low speed diamond saw \. The plates were divided into three groups, and three different surface treatments were performed: (1) no treatment (NT); (2) airborne-particle abrasion with 110-μm alumina particles (SB); (3) silica coating with Rocatec soft system (aluminum oxide of 30 µm grain size modified with silica) (CT). Each group was further subdivided into two subgroups according to the resin cement; Panavia v5 with clearfil primer plus (Kurary, Japan) and RelyX Unicem (3M/ESPE, USA). Then, ten composite resin cylinders (0.8-mm diameter × 0.5-mm height) were light-polymerized onto the ceramic plates in each subgroup. Each specimen was subjected to a shear load at a crosshead speed of 0.5 mm/min until fracture occurred. The fracture sites were examined with scanning electron microscopy (SEM) to determine the location of failure during debonding and to examine the surface treatment effects. Data were statistically analyzed using two-way ANOVA and multiple comparisons were made using Fisher’s test at pResults. Micro-shear bond strength was significantly affected by the surface treatment and by the type of resin cement. Panavia v5 showed higher significant results in comparison to RelyX Unicem. Surface treatment with CT was highly significant with both cements, followed by SB and then by NT. SEM examination revealed predominantly cohesive failures within the resin cements for CT group, mixed failures within SB group and predominantly adhesive failure at the interfacial area within NT group.
Conclusions: The micro-shear bond strength of resin cement to partially stabilized zirconia ceramics varied significantly depending on the type of resin luting agent and surface treatment method. The tribochemical silica coating of zirconia surfaces in combination with MDP-containing primer- resin cement (Panavia v5) showed a superior performance