A 7.5-year randomized controlled clinical study comparing cemented and screw-retained one-piece zirconia-based implant-supported single crowns

Objectives: To compare marginal bone levels, biological, and technical outcomes of screw-retained versus cemented all-ceramic implant-supported zirconia-based single crowns after an observation period of 7.5 years. Methods: Forty-four single implants in the esthetic zone in 44 patients (22 females, 22 males) were randomly assigned to two types of restorations: SR (screw-retained); veneered one-piece zirconia abutment and CR (cement-retained); veneered lithium disilicate crown intraorally cemented on a one-piece zirconia abutment. Patients were recalled annually up to 7.5 years and survival rates, biological, and technical parameters assessed. Results: A total of 31 patients attended the 7.5-year follow-up visit (17 SR group, 14 CR group). The survival rate on the restorative level was 77.5% (74.0% CR, 81.0% SR, p = .6399). Median marginal bone loss (MBL) values yielded -0.073 mm (-0.305; 0.238) in the CR and -0.215 mm (-0.500; 0.555) in the SR group (intergroup p = .6194). Mean bleeding on probing (BoP) values were significantly in favor of group SR with 20 +/- 17% compared to 40 +/- 22% in group CR (p = .011). The overall biological complication rate amounted to 27.5% (42.1% CR, 14.3% SR, p = .0775), whereas the technical complication rate was 32.5% (42.1% CR, 23.8% SR, p = .314). In total, CR restorations showed significantly more complications (84.2% for CR, 38.1% for SR, p = .0041). Conclusion: One-piece zirconia-based single crowns on two-piece dental implants exhibited a high rate of technical and biological complications at 7.5 years of follow-up. Cemented restorations revealed significant higher rates of bleeding on probing and total complications compared to screw-retained restorations.