Background and aim: Only few prospective studies have described the clinical performance of both zirconia-based implant-supported restorations and conventional metal-ceramic crowns with titanium or gold alloy abutments.
The purpose of this clinical study was to describe outcome variables of all-ceramic and metal-ceramic implant-supported, single-tooth restorations.

Material and methods: A total of 59 patients with tooth agenesis and with a mean age of 27.9 years treated with 98 single-tooth restorations supported by implants were included in the study. All patients were followed for three years. The implants supported 52 zirconia, 21 titanium and 25 gold alloy abutments, which retained 64 all-ceramic and 34 metal-ceramic crowns. At baseline and three-year follow-up examinations, the biological outcome variables such as survival rate of implants, marginal bone level, modified Plaque Index (mPlI), modified Sulcus Bleeding Index (mBI) and biological complications were registered.
The technical outcome variables included survival rate of abutments and crowns, marginal adaptations of crowns, cement excess and technical complications. The aesthetic outcome was assessed by the Copenhagen Index Score by using the scores for crown color match, crown morphology, mucosal discoloration and papilla index, mesially and distally. The patient-reported outcomes were recorded using the OHIP-49 questionnaire.
Results: The three-year survival rate was 100% for implants and 97% for abutments and crowns.
Significantly more marginal bone loss was registered at gold-alloy compared to zirconia abutments (P=0.040).The mPlI and mBI were not significantly different at zirconia, titanium and gold-alloy abutments.
The frequency of biological complications was higher at restorations with all-ceramic restorations and the marginal adaptations of all-ceramic crowns were significantly less optimal than metal-ceramic crowns (P=0.020).
The professional-reported aesthetic outcome demonstrated significantly superior color match of all-ceramic over metal-ceramic crowns (P=0.015). However, no significant differences in the other aesthetic parameters at various restoration materials were registered. After three years, the patient-reported outcome variables at different restoration materials were not significantly different.
Conclusions: The biological outcomes at the zirconia and metal abutments were comparable.
All-ceramic crowns demonstrated better color match, but higher frequency of marginal discrepancy compared to metal-ceramic crowns.
Generally, the patients noticed no difference in aesthetic outcome of all-ceramic and metal-ceramic restorations.

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