A Comparative Evaluation of Shear Bond Strength of Veneered Ceramic on Zirconia Core, with Various Surface Treatment: An In Vitro study

INTRODUCTION: Ceramic represents one of the growing sites in the field of dentistry. Dental ceramics were first used in dentistry in the late1700s. Use of ceramic started along with metal as substructure. Metallic restorations had superior strength but unaesthetic qualities, where as pure ceramic had superior esthetic but brittle in nature. In order to overcome this inherent weakness of poor color of the metal and brittle nature of the ceramics both the materials were blended in combinations. Several methods to increase the bond strength between metal and porcelain has been reported in literature. Despite of getting appropriate bond strength, metal ceramic restorations also had other disadvantages like reduced transmission of light through the restoration, allergic reactions, gingival discoloration around abutment tooth. To overcome all such disadvantages, the metal free ceramic restorations or al l ceramic restorations were introduced. The introduction of zirconia in the field of dentistry have paved the way to fabricate prosthesis with superior properties and excel lent results. In spite of having excel lent mechanical properties, refractory index of Zr is high, which makes it difficult to match the natural esthetics of the adjacent tooth. To overcome this drawback, layering of zirconia core is essential which gives a more natural appearance than Zr core. However sufficient bond strength is the basic criteria between the veneering ceramic and the substructure for a long term clinical success rate of zirconia restorations. Literature shows many studies dealing with the influence of different surface treatments on bonding quality. But an appropriate comparative study is needed among different surface treatment to increase clinical success rate of zirconia restoration. AIM OF THE STUDY: The aim of this study is to evaluate the effect of different surface treatments like liners, laser irradiation and acid treatment on shear bond strength (SBS) of zirconia core to veneered ceramic. MATERIALS AND METHODS: A total of 60 samples of Zirconia core were standardized by taking zirconia disc of 7mm diameter and 3mm height , which were divided into 3 groups (20 each) based on three different surface treatment - Lasers, liner and acid etching. Each group were further divided based on type of layring: One with lithium disilicate veneering and the other one with leucite veneering further dividing 20 samples into 10 each. RESULTS: 1. In case of Leucite veneered to zirconia core, acid treated surface showed highest shear bond strength. 2. In case of Lithium Disilicate veneered to zirconia core, laser treated surface showed highest shear bond strength. 3. When mean difference of bond strength of leucite among the study groups was assessed, bond strength of leucite was statistically insignificant. 4. When mean difference of bond strength of lithium disilicate among the study groups was assessed, the bond strength of lithium disilicate was statistically significant