Shear Bond Strength of Composite Repair System to Bilayered Zirconia Using Different Surface Treatments : (In Vitro Study) /

Abstract

The modern need for better esthetic restorations has increased especially with latest advances in sciences of materials and in methods and techniques of construction. Concerns regarding biocompatibility of the metal ceramic restorations along with its esthetic qualities created the need for development of better all ceramic systems that can provide function and esthetics with no compromises. Reinforcing glass ceramics and introducing tougher materials like zirconia proved to be a good alternative in molar and posterior region and in long span bridges. However with the need for good esthetic outcome zirconia restorations which had high strength properties did not deliver the ideal optical properties as they are opaque in nature and does not permit passage of the light as natural teeth would allow which necessitates the need for an esthetic solution for this drawback. The first solution was to layer the zirconia framework with a higher translucency material to permit passage of light and mimic the natural teeth shade for better esthetic restorations. The need for esthetics in stress bearing areas lead to the usage of monolithic zirconia to prevent the drawbacks of porcelain chipping The suggested material that can be layered was feldspathic porcelain which come in a form of a powder and a liquid which would be mixed together and layered layer by layer on top of the surface of zirconia and fire it in a specific porcelain oven. The other method was over pressing a pressable ceramic material on top of the surface of zirconia with a higher strength pressable ceramic material. The high fracture rate of the veneering porcelain from zirconia frameworks compared to porcelain fused to metal restorations necessitates the need for research into repair and finding a faster and efficient means for repairing zirconia. Methods of repair are divided into repair immediately at the clinic or repair at the lab by adding new layers of porcelain. Immediate repair in the clinic is the most favorable as it will save chair time and patients time. Immediate repair in the clinic comprises the use of different surface treatment methods to increase the roughness of the surface and increase the amount of shear bond strength. Laser surface treatment recently was used as a new method to increase surface roughness of the ceramics and to improve the bond strength during intraoral repair to be a more practical option rather than surface treatments as air abrasion or silica coating. Composite resin is the material used for immediate repair of fractured veneering porcelain with the use of silane coupling agent to promote good bond strength between fractured porcelain or framework and the composite resin. The choice of composite resin is due to its ability to bond and its esthetic properties. This study will be focused on evaluating methods of surface treatment of both zirconia and porcelain and their effect on bond strength to composite used for repair.