Cemented vs. screw‐retained single implant all‐ceramic crowns: 5‐year results of a clinical RCT

Abstract

Background: In order to overcome esthetic limitations of metal-ceramic implant reconstructions, all-ceramic crowns were introduced. Zirconia abutments demonstrated particular esthetic advantages, predominantly in cases with thin facial mucosa. Custom-made zirconia abutments can be combined with a cemented crown or, as an alternative, be directly veneered and inserted as a screw-retained reconstruction. Up to date, in clinical studies, NOe of the retention types could show a clear advantage over the other. Aim/Hypothesis: To test whether or not screw-retained all-ceramic implant-supported single crowns present similar biological and technical outcomes to cemented all-ceramic crowns after a follow-up time of 5 years. Materials and Methods: Forty-four two-piece dental implants with non-matching implant–abutment junctions were placed in single tooth gaps in the esthetic zone. Patients randomly received a screw-retained (SR) or cemented (CR) all-ceramic single reconstruction. Follow-up visits were scheduled 1–3 weeks after crown insertion, as well as at 6 months, 1, 3 and 5 years. Biological and esthetic parameters were assessed at the implant and control sites (contralateral tooth). Technical outcomes of the reconstructions were evaluated according to modified USPHS (United States Public Health Service) criteria. In addition, profilometric measurements were performed with an image analysis software. Data were statistically analyzed with Wilcoxon-Mann-Whitney, Wilcoxon and Fisher exact tests. Results: Out of 44 included subjects, 3 patients (6.8%) were not available for the 5-year follow-up (2 SR, 1 CR group). Eight reconstructions (18.1%) were lost due to technical (13.6%; 2 CR, 4 SR group; implants still present) or biological complications (4.5%; 2 CR group; implant loss). A total of 33 subjects could be reexamined. No significant differences regarding technical, radiographic and profilometric outcomes could be shown between the groups (P > 0.05). Bleeding on probing (BOP) showed significant higher mean values at implant sites for the CR group (40.0 ± 47.1%) compared to the SR group (8.3 ± 19.2%; P = 0.034). The median marginal bone level was −0.4 mm (−0.5; −0.3) in the SR group and −0.4 mm (−0.8; −0.3) in the CR group (P = 0.582). Cemented reconstructions showed a statistically significantly higher biological complication rate (36.8%, SR 0.0%; P = 0.0022), as well as a significant higher overall complication rate (68.4%, SR 22.7%, P = 0.0049) compared to screw-retained reconstructions (SR). Conclusions and Clinical Implications: At 5-years, a high rate of technical and biological complications could be observed, in particular for cemented reconstructions. This retention type was associated with a higher rate of positive inflammatory parameters (BOP), as well as with a higher incidence of peri-implant diseases. On the long run, screw-retained reconstructions appear to be the preferred type of retention when using all-ceramic reconstructions in the esthetic zone. Acknowledgements: The investigators gratefully acknowledge Prof Dr. Jürg Hüsler for analyzing the data and Gisela Müller, study monitor at the Clinic of Reconstructive Dentistry, Center for Dental Medicine, University of Zurich, for the support. Keywords: biologic complications, technical complications, ceramic abutments, cemented, screw-retained.