A Comparison of the Accuracy of Fit of 2 Methods for Fabricating Implant-Prosthodontic Frameworks

Purpose: To compare the in vitro 3-dimensional (3D) accuracy of fit of laser-scanned Computer Numeric Controlled (CNC)-milled implant titanium frameworks to that of conventional cast frameworks. Materials and Methods: Nine cast frameworks were fabricated on the mandibular master casts of 9 patients with 5 implants each following the well-established conventional fabrication technique. The frameworks were then laser scanned, and 9 CNC-milled titanium frameworks matching the outline of the conventional frameworks were fabricated. The accuracy of fit of both framework types was measured using a contact-type coordinate measuring machine and a computer program developed specifically for this purpose. Statistical analysis was done by a series of paired t tests. Results: The laser-scanned CNC-milled frameworks showed significantly less distortion along the x-axis (transversal, dx) compared with the conventional frameworks (means: 33.7µm and 49.2 µm, respectively) (P = .011). The titanium frameworks also demonstrated significantly less distortion on the horizontal plane compared with the conventional frameworks (means: 56 µm and 85 µm, respectively) (P = .012). The dy (sagittal) and dz (vertical) axes and total 3D distortion (Œ/dx2 + dy2 + dz2) showed less distortion overall in the laser-scanned CNC-milled frameworks, but this was not statistically significant (mean: 22.3 vs 35.6 µm, 13.3 vs 59.2 µm, 51 vs 114.1 µm, respectively, for y, z, and 3D distortion). Conclusion: Within the limitations of this study, fabrication of an implant-prosthodontic framework using the CNC milling technique yields a more accurate fit than the currently used cast technique. In vivo studies are needed to investigate the clinical significance of this recorded difference.