Fracture Resistance of Titanium-Based Lithium Disilicate and Zirconia Implant Restorations.

PURPOSE: To evaluate the fracture resistance of a newer lithium disilicate abutment material. MATERIALS AND METHODS: A premolar-shaped implant crown was designed using CAD/CAM software, and four groups of implant and crown combinations were milled: (1) lithium-disilicate hybrid-abutment crown; (2) "screwmentable" lithium-disilicate hybrid abutment/lithium-disilicate crown with screw channel; (3) lithium-disilicate hybrid abutment/lithium-disilicate crown; and (4) zirconia hybrid abutment/lithium-disilicate crown (control). The specimens were cemented to a titanium-base implant system, subjected to thermocycling and cyclic loading, and fractured in a material testing device. RESULTS: The lithium-disilicate hybrid-abutment crown had significantly greater fracture load than all the other groups, which were not significantly different from each other. CONCLUSIONS: Based on fracture load, the new lithium-disilicate hybrid-abutment material may serve as a viable alternative to the use of zirconia as a hybrid-abutment material.

Microtensile bond strength of lithium disilicate to zirconia with the CAD-on technique.

PURPOSE: Recently, a novel technique was introduced to combine lithium disilicate and zirconia into one restoration. The purpose of this study was to compare the microtensile bond strength of veneering ceramic to a zirconia core in two techniques: the e.max® CAD-on technique and the Press-on technique. MATERIALS AND METHODS: Group A was prepared by veneering sintered zirconia blocks (e.max® ZirCAD) with lithium disilicate blocks (e.max® CAD) using the CAD-on technique according to manufacturer's instructions. Group B was prepared by taking sintered e.max® ZirCAD blocks and veneering them with fluorapatite glass-ceramic (e.max® ZirPress) using the Press-on technique according to manufacturer's instructions. Each block was loaded in a dynamic cyclic loading machine. The blocks were then sectioned into 1 × 1 mm(2) beams (n = 43) using a precision saw, thermocycled, and loaded in tension until failure on a universal testing machine. A mean and standard deviation were determined per group. Data were analyzed using an unpaired t-test (α = 0.05). RESULTS: The mean microtensile bond strengths were 44.0 ± 13.8 MPa for the CAD-on technique and 14.9 ± 8.8 MPa for the Press-on technique. Significant differences were found between the two groups (p = 2.7E-19). CONCLUSIONS: The CAD-on technique (lithium disilicate/zirconia) resulted in greater microtensile bond strength than the Press-on technique (fluorapatite glass-ceramic/zirconia).