Comparison of lithium disilicate and feldspathic CAD-on systems in implant-supported crowns: a combined mechanical testing and FEA study.

BACKGROUND

The aim of this study was to compare the failure loads and stress distribution of two different CAD-on systems used for implant-supported crowns.

METHODS

Implant-supported crowns were designed with CAD/CAM software (Cerec InLab V15.0) and fabricated using the CAD-on technique (n = 12 per group): Group ZF (zirconia core veneered with feldspathic ceramic) and Group ZL (zirconia core veneered with lithium disilicate ceramic). Following cementation onto titanium abutments, the restorations were subjected to failure load testing using a universal testing machine. Simultaneously, 3D models of FEA were generated to evaluate Von Mises, Maximum Principal, and Minimum Principal stress distributions across the restoration, implant, abutment, and supporting bone. The mean failure loads were compared using the independent samples t-test (p < 0.05).

RESULTS

Group ZL exhibited significantly higher failure loads (4649.22 ± 733.42 N) compared to Group ZF (2085.91 ± 555.61 N) (p < 0.001). While stress concentrations were primarily located at the implant neck in both groups, the distribution on the abutments differed significantly. In Group ZF, delamination was the primary failure mode (100%), whereas Group ZL presented bulk fractures and abutment deformation.

CONCLUSION

While the Group ZL exhibited significantly superior failure load, the veneer delamination observed in Group ZF could act as a protective failure mode. Although the FEA revealed that different veneer ceramics did not alter the stress distribution across the implant and the bone, the selection of restorative system should ideally balance high fracture resistance with the biomechanical safety of the implant components.