FRACTURE RESISTANCE OF ULTRA TRANSLUCENT ZIRCONIA VERSUS LITHIUM DISILICATE IMPLANT SUPPORTED HYBRID ABUTMENT CROWNS TO TI BASE (AN IN-VITRO STUDY)

Aim of the study: to construct implant supported titanium based hybrid abutment crown from traditional lithium disilicate block/ultratranslucent zirconia disc with the help of five axis milling machine and to compare the fracture resistance of the two material.Materials and methods: A total number of 24 (implant with titanium base abutment) samples were made and divided into two groups :The first group received ultra translucent zirconia hybrid abutment crown (Z), the second group received lithium disilicate hybrid abutment crown (L). All samples were exposed to a thermocycling and cyclic loading, to measure the strenght of the two materials crown samples were subjected to a static load in universal testing machine parallel to the long axis of the tooth using a metallic rod covered by aluminum foil to distribute the forces evenly till fracture of the specimen. The collected data were arranged in tabular form and statistically analysed.Results: Implant supported ultratranslucent zirconia hybrid abutment crown showed significant higher fracture resistance (939.72 ± 70.99) than those of lithium disilicate hybrid abutment crown (874.88 ± 40.45) with (65.83 ± 23.59) difference as P=0.01, the results of both crowns showed readings above the clinical acceptable range(300-400N)Conclusions: Ultratranslucent zirconia showed higher fracture resistance than lithium disilicate hybrid abutment crown.