Mechanical Behavior of Posterior Implant Supported Restorations
This laboratory study was designed to evaluate the fatigue and fracture resistance of different CAD/CAM customized implant-supported restorations using two materials, monolithic zirconia and monolithic lithium disilicate and using two crown designs, hybrid-abutment-crowns and hybrid-abutments with separate crowns. Thirty-two implants were embedded perpendicularly in an auto-polymerizing resin. Thirty-two implant-supported restorations simulating a maxillary first premolar were designed and milled using a CAD/CAM system. These combinations were divided into two main groups according to type of material (n=16) zirconia and lithium disilicate. Each group was sub-divided into two subgroups according to design (n=8), i.e. hybrid-abutment-crown and hybrid abutment with a separate crown. Titanium bases were bonded to their respective abutments using auto-curing resin cement after specific surface treatment of the bonding surfaces. Each group was subjected to 1.2 million cycles of thermo-mechanical fatigue loading in a dual axis chewing simulator to simulate 5 years of clinical service. Surviving samples were loaded to fracture in a universal testing machine. Data was recorded, tabulated and analyzed. For the fatigue loading test, Fisher exact test. was used to study the effect of material and design on the fatigue resistance of different implant supported restorations. Test for data normality of fracture resistance test was done using Kolmnogrov- Smirnova and Shaprio-Wilk test. The data was not normally distributed. Accordingly, Mann-Whitney test was used to determine the effect of material, design and their interactions on the fracture resistance of the different implant-supported restorations and the following results was found: Zirconia implant-supported restorations had higher fatigue and fracture resistance median values than lithium disilicate. There was no significant difference between the fatigue and fracture resistance median values of hybrid-abutment-crowns and hybrid-abutments with separate crown.
Hybrid-abutments, Tibases, Implant-supported Restorations
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