An In-Vitro Study Evaluating the Fracture Resistance and Insertion Torque of Self-Drilling Mini-Implants Upon Insertion Into Synthetic High Density Mandibular Bone.

Introduction: Self-drilling mini-implants are commonly used in orthodontics, but there is little information regarding their fracture resistance in areas of high density bone without pre-drilling. Purpose: To determine the peak fracture torques of six commonly used self-drilling mini-implants, and to examine how each performs in extreme conditions without pre-drilling. Materials and Methods: Fifteen mini-implants from six different manufacturers were drilled into acrylic blocks using a custom-made insertion device incorporating a 6-DOF load cell for torque measurements. Peak fracture torques were recorded and compared for each of the six manufacturers. Additionally, ten mini-implants from each manufacturer were inserted into high density mandibular bone substitutes (Sawbones®) without pre-drilling. Measures of peak insertion torque for each manufacturer were recorded. Groups that experienced fracture upon insertion into the bone substitutes underwent further testing specifically following their manufacturer pre-drilling recommendations. Results: Resistance to fracture varied significantly among implants from different manufacturers. Tomas-pin and Aarhus experienced fractures during insertion into the non-pre-drilled bone substitutes. When manufacturer’s pre-drilling recommendations were followed, Aarhus continued to experience fractures during insertion. Conclusions: Unitek, Vector TAS, Dual Top, and Ortho Easy can be inserted into areas of thick and dense cortical bone without pre-drilling. Tomas-Pin can be inserted provided manufacturer pre-drilling recommendations are followed. The manufacturer\u27s recommendations for the use of 1.5mm Aarhus in areas of thick cortical bone may need to be modified