EFFECT OF LUTING AGENT VISCOSITY ON BOND STRENGTH AND MARGINAL GAB OF CERAMIC OCCLUSAL VENEER RESTORATIONS

Objectives: The purpose of this study was to evaluate the effect of viscosity of composite resin as luting agent before and after heating on bond strength and marginal gab of two CAD/CAM posterior ceramic occlusal veneers restorations. The effect of heating on the flow of composite resin was determined.
Materials and Methods: 20 e. max and vita enamic discs (4x4x2mm) was prepared (Isometric 4000 micro saw Buhler USA) and cemented to grind enamel surface of mounted molars groups (heated and non-heated composite )according to manufacturer instructions and bond strength was measured by testing machine (Model 3345; Instron Industrial Products, Norwood, USA). also 20 extracted human premolars was prepared for occlusal veneers and the constructed e. max and vita enamic CAD/CAM was bonded using flowable composite resin cement before and after heating then marginal gap was measured before and after thermo-mechanical aging .The interface of debonded surfaces was recorded. Internal gap was measured before cementation by a replica technique. Flow of composite resin was measured before and after heating using compressed composite discs (ANSI\ADA Specification No. 57 -1993). The data was tabulated and analyzed statistically.
Results: It was found that heating affected resin flow significantly (p=0.0003 < 0.05) as indicated by t-test where (heated resin mean value > non-heated resin mean value). Effect of heating of composite resin; totally it was found that heated composite resin affected marginal gap significantly (p=0.0284 < 0.05) where (non-heated resin mean value > heated resin mean value). Regardless to ceramic material groups, it was found that heated composite resin affected bond strength significantly (p=0.0141 < 0.05) as indicated by two way ANOVA test where (heated resin mean value > non-heated resin). Interaction between variables was not done coz the F value of ANOVA test showed non-significant interaction (p=0.2611>0.05)
Conclusions: Heating of flowable composite resin as luting before cementation improve the flow characteristics of composite resin, increase the bond strength of occlusal veneers, and reduce the marginal gab.