Dimensions Define Stability: Insertion Torque of Orthodontic Mini-Implants: A Comparative In Vitro Study

Background: Mini-implants have transformed orthodontic treatment by providing reliable anchorage and addressing challenges in anchorage control. This in vitro study aimed to compare the insertion torque (IT) values of three types of orthodontic mini-implants. The null hypothesis stated that no significant difference would be found in IT based on mini-implant type. Methods: We analyzed the mechanical ITs of 12 mini-implants categorized into four groups based on lengths (6, 8, 10, and 12 mm) and diameters (1.4, 1.6, and 2.0 mm). Mini-implants were inserted at a 90° angle into artificial bone (Sawbones^®) without pre-drilling. The ANOVA and Tukey's post hoc test assessed differences, and Spearman's correlation evaluated relationships between IT, diameter, and length. Results: The Lomas Mondefit^® 2 × 8 mm mini-implant had the highest IT (35 N), while the Jeil 2 × 12 mm had the lowest. Torque correlated with diameter (ρ = 0.609, p = 0.047) and length (ρ = 0.890, p < 0.001). The ANOVA showed significant differences (p = 0.035), with Leone^® and Lomas Mondefit^® differing significantly (p = 0.029). Mini-implant dimensions strongly influence IT. Conclusions: Mini-implant diameter and length significantly influence IT, highlighting their importance in clinical applications for optimal stability and performance.