Posterior CAD-CAM Cobalt-Chromium Single Crowns: 30-month Prospective Clinical Study

Objectives: The aim of this prospective study was to evaluate the clinical performances of CAD-CAM Co-Cr single crowns on natural teeth after 30 months of service.
Methods: Twenty-five single crowns replacing a posterior tooth were used in 25 patients. Tooth preparations were standardized and CAD-CAM Co-Cr frameworks were made and veneered with feldspathic ceramic. The restorations were luted using zinc-oxide cement. The patients were recalled after 1, 6, 12, 24 and 30 months. The survival and success of the restorations were recorded. The technical and aesthetic outcomes were assessed using the USPHS criteria. The biologic outcomes were analyzed at abutment and contralateral teeth and descriptive statistics were performed.
Results: All of the 25 Co-Cr single crowns were examined during 30 months of clinical function. No patient was lost at follow-up or censored. As to the technical drawbacks, neither fractures of the frameworks nor losses of retention were observed. Both the cumulative survival and success rates were 100% after 30 months according to Kaplan-Meier. No losses of retention were recorded. Twenty-four restorations were rated alpha in all measured parameters. No chipping of the ceramics was detected. According to the Wilcoxon test, the periodontal parameters of the test and the control teeth were not significantly different. Furthermore, the single crowns had no effect on the periodontal parameters after 30 months of clinical function.
Conclusions: Within the limitations of the present study and its observational period, the excellent survival rate of single posterior Co-Cr frameworks made with CAD-CAM technique allows to address this kind of restoration as a valid treatment option in posterior areas and a viable alternative to noble metal-ceramic single crowns.