Effect of Sterilization on Stability of Anodized and Non-Anodized Mini-Screws

Objective: To determine if autoclave sterilization has any deleterious effects on the clinical stability of anodized versus non-anodized mini-screws.

Method: Thirty anodized and thirty non-anodized Aarhus System mini-screws (American Orthodontics, Sheboygan, WI) were divided into six test groups of ten units each. One group of ten anodized mini-screws and one group of ten non-anodized mini-screws were sterilized once using a steam autoclave to serve as the control group.  The first test group of ten anodized and ten non-anodized mini-screws were cycled five times in the autoclave.  The second test group of similar makeup was sterilized ten times. All sixty mini-screws were inserted at a 90° angle into custom-designed synthetic blocks that simulated the average mandible of a healthy adult. The maximum insertion torque and the lateral displacement at 0.025, 0.05, 0.1, 0.25, 0.5, and 1.0 mm were recorded for each sample and subjected to statistical testing.  A two-way ANOVA, and a three-way mixed ANOVA were used for statistical analyses.  The level of significance was set at p<0.01.

Result: Maximum insertion torque values displayed significant differences between the anodized and non-anodized groups (p<0.001) as well as the sterilization cycles (p<0.001).  No significant group and cycle interaction was observed.  Furthermore, no significant differences were found between the test groups, sterilization cycles, force required for lateral displacement, or group interactions in the evaluation of the lateral displacement tests.

Conclusion: Comparison of anodized to non-anodized mini-screws as they are sterilized up to 10 cycles revealed some differences that may not affect their consistency and clinical stability.