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In-Vitro Comparison of Implant-Supported Single Crowns and Abutments Manufactured with Different Techniques
Of the late years, modified-hybrid restorations in which the abutment and crowns are manufactured as one-piece and screwed to the implant are referred to as “hybrid-abutment-crowns”. Another modification of the hybrid-abutment-crown design is that the veneer porcelain is baked directly onto the abutment and screwed to the implant. In this study, the fracture strengths of implant-supported single-crown restorations manufactured with different materials and techniques are evaluated.
2) Materials and Methods
40 implants were divided into four groups according to the abutment material and production technique. (PrefabTi: prefabricated titanium abutment and screwmentable titanium substructured porcelain crown; FabZr: prefabricated zirconia abutment and screwmentable zirconia substructured porcelain crown; CADCAMTi: Hybrid-abutment-crown obtained by baking veneer porcelain directly on the titanium representative abutment manufactured by CAD/CAM; CADCAMZr: Hybrid-abutment-crown obtained by baking veneer porcelain directly on a zirconia representative abutment manufactured by CAD/CAM and supported with Ti-base) Restorations were manufactured in accordance with the upper 1st premolar morphology. Following the thermocycle process, the fracture strength measurements were carried out. Fracture mode analyzes were performed with digital microscope and radiographic examination.
The group with the highest fracture strength is CADCAMTi group with 385,8427,68 N. This group is followed by 313,1839,97 N; 272,6935,03 N and 156,7119,83 N for the CADCAMZr, PrefabTi and PrefabZr groups, respectively. The differences between the mean fracture strength of the groups were found to be statistically significant. The most common failure mode in the PrefabTi group was deformation of the screw, hex and implant. Internal-hex level fracture was observed in all of the samples in the PrefabZr group. While the most common failure mode in the CADCAMTi group was restoration fracture accompanying screw, hex, and implant deformation; most of the specimens in the CADCAMZr group showed sepratation of the abumtment-crown complex from Ti-base and deformation of the titanium components.
The fracture strengths of hybrid-abutment-crowns obtained as single piece were found to be significantly higher than screwmentable crowns. It can be said that the production of the system in one-piece instead of two-pieces increases the fracture strength.