Randomized Controlled Clinical Trial of All-Ceramic Single-Tooth Implant Reconstructions Using Modified Zirconia Abutments: Results at 5 Years After Loading

The objective of this trial study was to assess whether submucosal veneering of internally connected zirconia abutments influences clinical, radiographic, and technical outcomes of single-tooth implant-borne reconstructions at 5 years after loading. A total of 20 patients with 20 single-tooth implants in the anterior or premolar area of the maxilla or mandible were included. The implants were randomly restored with fixed single-tooth reconstructions using either pinkveneered customized zirconia abutments (test group = 10) or nonveneered customized zirconia abutments (control group = 10). All reconstructions were adhesively cemented with all-ceramic crowns. Follow-up examinations were performed at baseline (7 to 10 days after crown insertion) and at 1, 3, and 5 years after loading, at which points the following were assessed: periodontal parameters such as probing depth (PD), bleeding on probing (BOP), and marginal bone levels, as well as technical outcomes using the modified United States Public Health Service (USPHS) criteria. Statistical comparisons were based on the Wilcoxon- Mann-Whitney test. Sixteen patients attended the 5-year follow-up. At 5 years, the implant survival rate was 100% and the prosthetic survival rate was 94.1% (one abutment fracture in the test group). Veneering of the submucosal part of zirconia abutments resulted in significantly higher mean PD values: 3.6 ± 0.4 mm (test group) and 3.0 ± 0.5 mm (control group), P = .042. Marginal bone levels at 5 years and changes up to 5 years were not significantly different between groups (P > .05). One crown exhibited an abutment fracture and two crowns a minor chipping (17.6% overall technical complication rate). Limited by a small sample size, veneering of the submucosal part of internally connected zirconia abutments led to outcomes that were less favorable biologically (PD, BOP, and KM), but similar to nonveneered abutments radiographically and technically.