Effect of Implant Angulation on Digital Impression Accuracy of Three-Unit Implant-Supported Restorations

Introduction and Aims: This study evaluated the effect of implant angulation on the accuracy of digital impressions for 3-unit implant-supported fixed partial dentures obtained with 2 intraoral scanners. Methods: Three partially edentulous maxillary resin casts with 4 implants placed bilaterally at the first premolar and first molar sites were prepared with inter-implant angulations of 0° (parallel), 15°, and 30°. Scan bodies were attached and reference scans were obtained using an optical coordinate-measuring system. Each cast was scanned 12 times with 3Shape TRIOS 3 and CEREC Omnicam AC scanners. The datasets were superimposed onto the reference models, and linear and angular deviations were calculated. Data were analysed using generalized estimating equations (GEE) to evaluate the effects of implant angulation, scanner type, and implant pair. Results: Implant angulation significantly affected digital impression accuracy. For linear deviation, the GEE model showed a significant cast × scanner interaction (β = 0.028; 95% CI, 0.017–0.039; p < .001). TRIOS 3 produced greater deviations than Omnicam at 0° and 15° (mean differences 0.029 mm and 0.018 mm), whereas it showed lower deviation at 30° (–0.027 mm). Linear deviations ranged from 0.50 to 0.68 mm. For angular deviation, no cast × scanner interaction was found (β = 0.017; 95% CI, –0.008-0.043; P = .078), but implant angulation had a significant effect (β = –0.628; 95% CI, –0.917 to –0.338; P = .001), with lower deviations at higher angulations (0.05°–0.06°). Scanner type and implant pair did not significantly affect angular accuracy. Conclusions: Implant angulation influences the linear and angular accuracy of digital impressions for short-span implant-supported restorations. Within the limitations of this in vitro study, moderate implant angulations (15°-30°) did not adversely affect angular accuracy or compromise digital impressions of short-span implant configurations. Clinical Relevance: Moderate implant angulation does not appear to compromise the accuracy of digital impressions of short-span implant-supported restorations, supporting the clinical use of intraoral scanners in situations where implant angulation is dictated by anatomical or surgical constraints.