A practice‐based clinical evaluation of the survival and success of metal‐ceramic and zirconia molar crowns: 5‐year results

This practice‐based study evaluates the survival and success of conventionally luted metal‐ceramic and zirconia molar crowns fabricated by using a prolonged cooling period for the veneering porcelain. Fifty‐three patients were treated from 07/2008 to 07/2009 with either metal‐ceramic crowns (MCC) or zirconia crowns (ZC). Forty‐five patients (26 female) with 91 restorations (obser‐vational period: 64·0 ± 4·8 months) participated in a clinical follow‐up examination and were included in the study. Estimated cumulative survival (ECSv), success (ECSc) and veneering ceramic success (ECVCSc) were calculated (Kaplan–Meier) and analysed by the crown fabrication technique and the position of the restoration (Cox regression model) (P < 0·05). Five complete failures (MCC: 2, ZC: 3) were recorded (5‐year ECSv: MCC: 97·6%, (95% confidence interval (95%‐CI): 93%; 100%]/ZC: 94·0%, (95%‐CI): 87%; 100%]). Of the MCCs (n = 41), 85·0%, 95%‐CI: (77%; 96%)] remained event‐free, whereas the ECSc for the ZCs (n = 50) was 74·3% (95%‐CI): 61%; 87%]. No significant differences in ECSv (P = 0·51), ECSc (P = 0·43) and ECVCSc (P = 0·36) were detected between the two fabrication techniques. Restorations placed on terminal abutments (n = 44) demonstrated a significantly lower ECVCSc (P = 0·035), (5‐year VCF‐rate: 14·8%) than crowns placed on tooth‐neighboured abutments (n = 47), (5‐year VCF‐rate: 4·3%). In the present study, zirconia molar crowns demonstrated a 5‐year ECSv, ECSc and ECVCSc comparable to MCCs. Irrespective of the fabrication technique, crowns on terminal abutments bear a significantly increased risk for VCFs. Clinical investigations with an increased number of restorations are needed.