Investigation the effect of abutment size and infrastructure-superstructure thickness on the fracture strength of posterior implant supporting zirconia crowns

CAD/CAM zirconia restorations are one of today's most advanced dental materials. The most common technical failure in zirconium restorations is chipping or cracking of superstructure porcelain. The aim of this study is to investigate the effects of varying infrastructure and superstructure thickness on fracture resistance in posterior single implant-supported cemented crowns. In this study, two standard abutments (Height: 4 mm, Width: 6.5 m; Height: 5.5 mm; Width: 6.5 mm, Gingival heights fixed: 1 mm) (ITI Straumann, Bone-level, Switzerland) and one anatomic abutment (Height: 6 mm, Width: 6.5 mm, Gingival height: 1 mm) were used. Zirconia infratructure veneer restorations with different infrastructure/superstructure thickness and a particular vertical dimension were prepared. As control group; 0.5 mm thick zirconium and metal infrastructures were prepared for short abutment and 1.5 mm thick porcelain veneers were processed on them. A total of 96 pieces of veneer crowns (n=8) were prepared. These veneer crowns were cemented with temporary cement (TempBond, Kerr, USA) and then they were subjected to fracture strength testing in a universal testing machine. Fracture type and shape were examined with optical and SEM microscopy. Data analysis was completed using Kruskal-Wallis and Mann-Whitney U test. In which the thickness of infrastructure and superstructure prepared on the short abutment showed equal distribution, has the highest fracture resistance with 3592,64 ± 722,61 N. The lowest value in terms of fracture resistance was 418,67 ± 89,79 N. and obtained from the samples which has 0.5 mm thick metal infrastructure prepared on anatomical abutments. It is determined that the fracture resistance of zirconium restorations which have a thicker infrastructure than 0.5 mm significantly increases.