Cemented versus screw-retained implant-supported single-tooth crowns: a 10-year randomised controlled trial

Purpose: The purpose of this randomised controlled trial was to compare the long-term clinical outcome of cemented and screw-retained implant-supported single-tooth crowns. Materials and methods: Eighteen consecutive patients presenting with single-tooth bilateral edentulous sites in the canine/molar region with adequate bone width, similar bone height at the implant sites, and an occlusal scheme that allowed for the establishment of identical occlusal cusp/fossa contacts were treated. Each patient received two identical implants according to a split-mouth design. One side was randomly selected to be restored with a cemented implant-supported single crown, and the other was restored with a screw-retained implant-supported single crown. Outcome measures were implant success, complications, marginal bone levels and peri-implant soft tissue health. Results: Ten years after initial loading, 2 patients moved away and were lost to follow-up. Two implants placed in the same patient failed 5 years after their insertion; the remaining 30 implants survived, resulting in a cumulative implant success rate of 93.7%. No complication occurred. The mean marginal bone resorption at 10 years after implant placement, measured on intraoral radiographs, was 1.1 ± 0.2 mm for both types of restorations. There were no statistically significant differences between the two groups with respect to peri-implant marginal bone level at the 10-year follow-up appointment (T2) (P = 0.58); at the 4-year follow-up appointment (T1) a statistically significant difference was observed (P = 0.01), but this was not considered clinically relevant (mean difference: -0.06 mm). The status of the soft tissue around the implants remained stable over the evaluation period. No statistically significant difference was identified for the facial keratinised gingiva between the two groups at T1 (P = 0.10) or at T2 (P = 0.07). Conclusions: Within the limitations of this study, the results indicate that there was no evidence of a significant difference in the clinical behaviour of the peri-implant marginal bone or of the peri-implant soft tissues when cemented or screw-retained single-tooth implant restorations were provided. Keywords: cement-retained crowns, dental implants, screw-retained crowns, single implant-supported crowns