BRIEF RESUME OF INTENDED WORK
6.1 NEED FOR THE STUDY:
The increase of patient’s desire for aesthetics has resulted in the use of all ceramic restorations in the posterior as well as anterior region. The acceptance of all ceramic restorations has increased because of their inherent aesthetics,
excellent biocompatibility , improved physical properties and mechanical properties. The shear stress formed in the sintered zirconium causes martensitic transformation, inhibiting opening of the crack and increasing the energy necessary for further crack growth. Variety of cements are available today but the information about the retentive strength of these cements is limited. Hence this study is under taken to determine the ability of these cements to retain zirconium oxide ceramic crowns .
6.2 REVIEW OF LITERATURE :
A study was conducted on the retention of zirconium oxide ceramic crowns
with three types of cements.The study concluded that within the limitations of this study , the 3 luting agents with mean removal stresses ranging 5.0 to 6.1 MPa were not significantly different .The use of a composite resin cement with a bonding agent did not yield higher coping retention compared to other 2 cements.1
An invitro study was conducted on retentive strength of zirconium oxide ceramic crowns using different luting agents. The study concluded that the compomer cement ,the resin modified glass-ionomer cement and the self adhesive resin luting agent had the same level of retentive quality as the resin luting agents, superbond C& B,and panavia. Rocatec pre-treatment of the ceramic surface did not improve the retentive strengths of compolute and superbond C& B.2
A study was conducted on bond strength of luting cements to zirconium oxide ceramics. The study concluded that the bond strengths for twinlook and panavia 21 were quite low ,and only superbond showed a clinically acceptable bond strength .3
A study was conducted on reliability and properties of ground yttria –stabilized tetragonal zirconia polycrystals ( Y-TZP) – zirconia ceramics. The study concluded that inner surface grinding significantly reduces the strength and reliability of Y-TZP zirconia compared with the lapped controls.4
An invitro study was conducted to evaluate shear bond strengths of resin to densely- sintered high purity zirconium oxide ceramic after long term storage and thermal cycling. The study concluded that artificial aging significantly reduced bond strength. A bonding/ silane coupling agent containing an adhesive phosphate monomer can achieve superior long term shear bond strength to airborne –particle abraded procera all zircon restoration with either one of the 2 resin luting agents tested.5
6.3 OBJECTIVES OF THE STUDY :
To evaluate and compare shear strength of three different cements
used for luting zirconium oxide ceramic crowns.