Objectives
The primary aim was to investigate survival rate of zirconia versus metal abutments, and the secondary aim was clinical outcomes of all-ceramic versus metal-ceramic crowns on single-tooth implants.

Methods
Patients with tooth-agenesis participated to previously published prospective clinical study with 3-year follow-up were recalled after 5 years. Biological variables included survival and success rate of implants, marginal bone level, modified Plaque and Sulcus Bleeding Index and biological complications. Technical variables included restoration survival rate, marginal adaptation and technical complications. The aesthetic outcome of crowns and peri-implant mucosa in addition to patient-reported outcome were recorded. Descriptive analysis, linear mixed model for quantitative data, or generalized linear mixed model for ordinal categorical data were applied; significance was set to 0.05.

Results
Fifty-three patients (mean age: 32.4 years), with 89 implants participated to the 5-years examination. The implants supported 50 zirconia abutments with 50 all-ceramic (AC) crown and 39 metal abutments with 29 metal-ceramic (MC) and 10 AC crowns. The Implant and restoration survival rate was 100% and 96%, respectively. No clinically relevant biological difference between implants supporting metal or zirconia abutments was registered. The technical complications were veneering fracture of AC-crowns (n = 3), crown loosening of MC-crowns (n = 4) and one abutment screw loosening (MC-crown on metal abutment). MC-crowns had significantly better marginal adaptation than AC-crowns (p = .01). AC-crowns had significantly better color and morphology than MC-crowns (p = .01).

Conclusions
Zirconia-based single-tooth restorations are reliable alternative materials to metal-based restorations with favorable biological and aesthetic outcome, and few technical complications.