Influence of abutment-configuration on fracture strength of CAD/CAM-fabricated ceramic crowns

Aims: This in vitro study assessed the fracture strength of computer-aided designing (CAD)/computer-aided manufacturing (CAM)-fabricated crowns on implant-abutments with different configurations. Subjects and Methods: Out of 30, 15 implant-abutments were shortened to 2 mm and a ball-headin metal-alloy was fixed on each abutment. Single crowns (Vita Mark II, Empress CAD, e. max CAD, Lava Ultimate, artBloc Temp Merz Dental, Telio CAD, and Vita CAD Temp) were designed. After cementation of the crowns using RelyX Unicem, a Zwick universal testing machine was used to aplicate occlusal force until the ceramic material was destroyed. Statistical Analysis Used: Statistical analysis were performed using analysis of variance (α =0.05) and Bonferroni correction. Results: This study has confirmed significant increases in fracture strength of crowns made of ceramic materials using the ball-head abutmentc on figuration. Conclusion: Within the limitations of this in vitro study, the following conclusions can be drawn: (1) The fracture strength of CAD/CAM-fabricated all-ceramic crowns could be increased using a rounded abutment up to 1.6 times. (2) The fracture strength of CAD/CAM-fabricated polymers could not be enhanced using a ball-head abutment. The increase of the fracture strength of all-ceramic crowns using the rounded abutment, could give reasons for the producers of implant abutments to improve their abutment design.