CAD/CAM-titanium-ceramic single crowns with non-anatomic coping-design. A six-year follow-up study

Objectives: The adhesive bond between casted titanium and porcelain was compromised due to the existence of reactive layers. Furthermore the titanium's coefficient of thermal expansion is significantly lower than that of conventional noble metal alloys, therefore titanium required special low-fusing porcelain with a low coefficient of thermal expansion to be veneered. Modern titanium copings were fabricated using CAD/CAM technology. Earlier versions of CAD software were limited to design non-anatomic metal copings in even thicknesses. The present study reports the clinical results of CAD/CAM titanium-ceramic single crowns with non-anatomic coping design. Fractures of the veneering porcelain were examined after a follow-up of six years. Methods: 41 crowns were fabricated for 21 patients. The titanium copings were CAD/CAM milled (Everest CAD/CAM system, KaVo) with an even thickness of 0.5mm, veneered with low-fusing veneering porcelain (Vita Titanium Porcelain, VITA Zahnfabrik) and cemented using zinc phosphate cement. The patients were recalled yearly to examine for the presence of any complications. The success and survival rates were estimated using the Kaplan-Meier analysis[2]. Results: At the 6-year recall 3 patients (4 crowns) were lost to follow-up. Mechanical complications summed up to 10 cohesive and 2 adhesive porcelain fractures that resulted in the replacement of 2 crowns. The fractured crowns were found in 1 anterior crown and 11 posterior crowns. The 2 crowns that needed to be replaced were both posterior crowns, and the fracture of the porcelain caused loss of either occlusal or proximal contact. One biologic complication was found during the follow-up examinations. The Kaplan-Meier cumulative success rate of CAD/CAM titanium-ceramic crowns with regard to mechanical complications was 67.8%±7.7SE. The Kaplan-Meier cumulative survival rate of CAD/CAM titanium-ceramic crowns with regard to function was 91.3%±4.8SE. Conclusion: The clinical performances of the CAD/CAM titanium-ceramic crowns with nonanatomic coping design for 6 years were poor. To avoid veneering porcelain fracture modern CAD-software with tools to design proper coping should be used. Keywords: coping design, CAD/CAM titanium-ceramic crowns, low-fusing porcelain