Fracture resistance of commonly used self-drilling orthodontic mini-implants

• Published in: The Angle orthodontist Vol. 85; no. 1; pp. 26 - 32
• Main Authors: Smith, Angie, Hosein, Yara K, Dunning, Cynthia E, Tassi, Ali
• Format: Journal Article
• Language: English
• Published: United States Edward H Angle Education and Research Foundation, Inc 01-01-2015
• Subjects: Dental Alloys - chemistry; Dental Implants; Dental Stress Analysis - instrumentation; Dentistry; Equipment Failure; Humans; Materials Testing; Miniaturization; Original; Orthodontic Anchorage Procedures - instrumentation; Orthodontic Appliance Design; Polymethyl Methacrylate - chemistry; Stress, Mechanical; Surface Properties; Time Factors; Titanium - chemistry; Torque; Fracture torque; Miniscrew; Insertion torque; Mini-implant; Orthodontics; Temporary anchorage device
• ISSN: 0003-3219; 1945-7103
• DOI: 10.2319/112213-860.1

To investigate the fracture resistance of six commonly used self-drilling orthodontic mini-implants by comparing their respective fracture torques during insertion.
Ninety self-drilling mini-implants from six manufacturers (Aarhus, Dual-Top, OrthoEasy, Tomas-pin, Unitek, and VectorTAS), with diameters ranging from 1.4 to 1.8 mm, were inserted into acrylic blocks using a custom-made insertion device. Insertion torques were measured using a 6-degree-of-freedom load cell fixed to the base of the acrylic blocks, and peak torques experienced at the time of fracture for each of the mini-implants were recorded. One-way analysis of variance (α  =  .05) was used to compare the fracture torques among the six different groups.
Statistical analysis revealed significant differences (P < .05) in the peak fracture torques among mini-implant groups. Mean fracture torques ranked as follows: Unitek (72 Ncm) > Tomas-pin (36 Ncm) > Dual-Top (32 Ncm) ≈ VectorTAS (31 Ncm) > OrthoEasy (28 Ncm) > Aarhus (25 Ncm), with significant differences found between all manufacturers, except for Dual-Top and VectorTAS.
Mini-implants tested showed a wide range of torque at fracture depending on the manufacturer, with only a weak correlation between mini-implant diameter and fracture resistance. This torque should be considered at the time of mini-implant insertion to minimize the risk of implant fracture, especially in areas of high-density bone without predrilling.