Resumen de Peak insertion torque values of five mini-implant systems under different insertion loads
Erma Quraishi, Martyn Sherriff, Dirk Bister
Objective: To assess the effect of 1 and 3 kg insertion load on five makes of self-drilling mini-implants on peak insertion torque values to establish risk factors involved in the fracture of mini-implants. Materials and methods: Two different loads were applied during insertion of 40 mini-implants from five different manufacturers (Dual Top� (1·6×8 mm), Infinitas� (1·5×9 mm), Ortho Easy� (1·7×8 mm), Spider Screw� (1·5×8 mm) and Vector TAS� (1·4×8 mm)) into acrylic blocks at 8 rev/min utilizing a Motorized Torque Measurement Stand. Results: Peak insertion torque values for both loads were highest for Vector TAS followed by Ortho Easy and Dual Top and were nearly three times higher than Infinitas (original version) and Spider ScrewsTM. The log-rank test showed statistically significant differences for both loads for Vector TAS, Ortho Easy and Spider Screws. Unlike other designs tested, both tapered mini-implant designs (Spider Screw and Infinitas) showed a tendency to buckle in the middle of the body but fractured at the tip. Conclusion: Non-tapered mini-implants fractured at significantly higher torque values compared to tapered designs under both loads. Increased pressure resulted in slightly higher maximum torque values at fracture for some of the mini-implant designs, although this is unlikely to be of clinical relevance. Tripling insertion pressure from 1 to 3 kg increased the risk of bending tapered mini-implants before fracture.
