Three-Year Follow-up of a Randomized Clinical Trial on Screw-Retained Monolithic Zirconia Restorations on Ti-Base Abutments Based on Digital or Conventional Impression Techniques

Purpose: To report on the follow-up of two previously published RCTs on the performance of screw-retained monolithic zirconia restorations on titanium (ti)-base abutments based on either digital scans through intraoral optical scanning (IOS) or conventional impressions. Materials and Methods: A total of 54 patients receiving 89 restorations (44 solitary crowns [SC], 21 splinted crowns [2-FDP], and 24 three-unit fixed partial dentures [3-FDP]) were included for the 1- to 3-year follow-up period. Restoration survival and technical complications were documented. Results: In total, 50 patients with 84 restorations completed the 3-year follow-up. One 3-FDP from the digital group was lost. This resulted in a survival rate of 97.9% for the digital group and 100% for the conventional group and an overall survival rate of 98.8% for screw-retained monolithic zirconia restorations on implants after 3 years. There was no statistically significant survival difference between the digital and conventional restorations (P =.362). When evaluated separately, a 100% survival rate of SCs and 97.7% for 2-FDPs could be reported. One decementation and three screw loosenings occurred in the 1- to 3-year follow-up. The multiple-implant restorations showed higher (23.3%) complication rates at the restoration level than the SCs (4.9%) after 3 years of function (P =.026). Conclusions: Screw-retained monolithic zirconia restorations on ti-base abutments show promising survival rates after 3 years of function. Restorative complications in screw-retained monolithic zirconia restorations on Ti-base abutments are more likely to happen in the first year of function and are more common in multiple-implant restorations than SCs. The impression type (digital or conventional) does not seem to influence these results.