Sterilization Effect on Axes and Distances Between Three Implants in Curved Lines When Using Two Types of Two-Piece Intra-Oral Scan Bodies: An In Vitro Study

Background: The aim of this in vitro study was to examine the effect of the sterilization process on two different two-piece intra-oral scan bodies (ISBs) using three-dimensional (3D) analysis. Methods: Two identical 3D-printed models with three analogs in positions #12, #13, and 14# were used: two-piece titanium (Ti-Ti) and two-piece poly-ether-ether-ketone (PEEK) and Ti (PEEK-Ti) ISBs. Each model was scanned once before sterilization. A laboratory scanner (LBS) produced a reference stereolithography (STL) file, followed by 30 scans with an intra-oral scanner (IOS), producing 30 STL files. Both ISBs underwent three cycles of sterilization followed by thirty scans using an IOS, producing another 30 STL files. Each STL file was superimposed on the LBS reference STL file using 3D analyzing software, and the following parameters were calculated: inter-implant distance, intra-implant distance, inter-implant angle, and intra-implant angle. The Kolmogorov–Smirnov test indicated non-normal distribution; therefore, Wilcoxon signed-rank tests and Mann–Whitney tests were performed (p < 0.05). Results: Within groups, after sterilization, the mean errors of the Ti-Ti ISB were significantly increased regarding inter-implant distance 12_13 (p < 0.05), intra-implant distance 14 (p = 0.0005), inter-implant angle 12_13 (p = 0.0005), inter-implant angle 13_14 (p = 0.001), intra-implant angle 13 (p = 0.005), and intra-implant angle 14 (p < 0.05). Within groups, after sterilization, the mean errors of the PEEK-Ti ISB were significantly increased regarding inter-implant distance 12_13, 13_14, and 12_14 (p = 0.0005), intra-implant distance 12 (p < 0.05), intra-implant distance 13 and 14 (p = 0.0005), inter-implant angle 12_13 (p = 0.0005), and inter-implant angle 13_14 (p = 0.005). Between groups, after sterilization, the mean errors for the PEEK-Ti ISB were significantly higher (p < 0.0005) regarding all parameters compared to the Ti-Ti ISB. Conclusions: Both PEEK-Ti and Ti-Ti ISBs showed significant changes in most parameters after three cycles of sterilization, with the PEEK-Ti ISB exhibiting greater changes compared to the Ti-Ti ISB. Therefore, three cycles of sterilization affect axes and distances for both PEEK-Ti and Ti-Ti ISBs.