Effect of angulation between multi-unit abutments on trueness of photogrammetry systems

Abstract

Purpose: To compare the trueness between conventional impressions (CI) and photogrammetry for full-arch implant-supported prosthesis and to evaluate the effect of increased inter-abutment angulation on trueness. Materials and Methods: Three edentulous reference models containing four multiunit abutment (MUA) replicas with different inter-abutment angulations were used: 0-degree (0D), 10-degree (10D), or 20-degree (20D). Three impression techniques were utilized on each model (n = 10): ICam4D-photogrammetry (IP), PIC-photogrammetry (PP), and CI. Standard tessellation language (STL) datasets of samples were created. A reverse engineering software (Geomagic ControlX; 3D Systems) was used to measure three-dimensional (3D) and angular deviations between samples and reference models. Means and standard deviations were calculated and analyzed using linear regression models. The significance level was set at p < 0.05. Results: The combined total mean 3D deviations were (29 ± 10 µm) for CI, (48 ± 7 µm) for PP, and (51 ± 8 µm) for IP. The combined total mean angular deviations were (0.16 ± 0.07 degrees) for CI, (0.46 ± 0.12 degrees) for IP, and (0.62 ± 0.23 degrees) for PP. Linear regression showed significant differences for 3D and angular deviations: The CI technique was significantly lower compared to PP and IP across all models (p < 0.001). Increased inter-abutment angulation showed significant differences within the PP and IP groups (p < 0.05), while no significant differences were seen within the CI groups (p > 0.05). Conclusion: Within the limits of the study, CI demonstrated statistically higher trueness compared to the two photogrammetry systems tested with up to 20 degrees of inter-abutment angulation, which may not be clinically significant. Increased inter-abutment angulation affected the photogrammetry scans to variable degrees.