Zirconia-based versus metal-based single crowns veneered with overpressing ceramic for restoration of posterior endodontically treated teeth: 5-year results of a randomized controlled clinical study

Objectives The aim of this 5-year randomized controlled trial was to compare the longevity and clinical behavior of single posterior crowns made with pressable ceramic on zirconia and on metal frameworks, and if failures occur, to delineate the contributing factors. Methods 72 patients, who needed the covering of at least a molar and/or premolar, were included in the study. All teeth were endodontically treated, with absence of periapical lesion or active periodontitis. Ninety single crowns were made with zirconia or metal framework and covered with pressable veneering ceramics. Two independent examiners assessed the survival of restorations at 6 months, 1–4 and 5 years after restoration placement including periapical radiographs, intraoral photographs, and USPHS modified criteria. The statistical analyses were performed with the Kaplan-Meier method. Results One core fracture occurred in Zircad/Zirpress crowns and one metal ceramic crown was lost for root fracture. Chipping fracture of the veneering ceramic was detected in 2 metal-ceramic crowns and in 3 zirconia-based crowns. The Estimate Cumulative Survival (ECS) and the Estimate Cumulative Success (ECSs) with standard deviation (SE) were respectively 97,73 ± 2,19 and 92,64 ± 4,14 for zirconia-based crowns whereas 97,44 ± 2,39 and 91,11 ± 4,27 for porcelain fused to metal crowns. Conclusions The present randomized controlled trial shows that the survival of zirconia-based and metal-based single crowns is similar over a follow-up period of 5 years. No significant differences in esthetic, functional and biological outcomes were demonstrated between the two groups. The main failure mode was the chipping fracture of the veneering ceramic in both materials. Study number on ClinicalTrial.gov NCT02758457. Clinical significance According to the results of this clinical study, zirconia-based rehabilitations with overpressing veneering technique represent a valid alternative to metal-based for posterior single crown restorations.