Positional Changes of Implant Scan Bodies after Repeated Sterilizations: An in vitro Study

Objectives: The aim of this in vitro study is to evaluate the magnitude and direction of positional changes of implant scan bodies (ISBs) after up to 50 repeated sterilization cycles, and to determine the clinical importance and recommendations for repeated use of ISB. Materials and Methods: Ten ISBs (PEEK at scan region and titanium base) and one 3D printed half-arch single tooth implant model with implant analogue placed in left second premolar were used. All ISBs were hand-tightened to the model prior to each sterilization according to the manufacturer’s recommendation. An initial scan prior to sterilization was set as control. All ISBs were scanned using a lab scanner after each sterilization. Displacement values in x, y, and z axes, oriented to the center of the scan region, were recorded after 0, 10, 20, 30, 40, and 50 sterilizations. Resulting positional deviations were compared using descriptive statistics, the non-parametric Friedman’s test, and the post-hoc Nemenyi test with Bonferroni adjustment for multiple comparisons. Results: Descriptive statistics indicates that the x-axis exhibited the least variability within and between specimens, while the y-axis showed the greatest variability. The median positional change of 10 specimens according to the number of sterilizations is less than 0.05mm on x-axis, 0.12mm on y-axis, and 0.035mm on z-axis. Positional deviations were globally statistically significant for all three axes. Post-hoc pairwise comparisons with Bonferroni correction were statistically significant at the 10th sterilization for the x axis (p= 8.2e-05), the 20th sterilization for the y axis (p= 0.007), and the 50th sterilization for the z axis (p= 0.023). Conclusion: Statistically significant change in ISB position may occur after repeated sterilization cycles. However, within the limitation of this study, the magnitude of the median change for x and z axes after 50 sterilization cycles may be clinically acceptable.