[Biomechanical Comparison of Self-drilling and Self-tapping Orthodontic Micro-implants]

Objective: To evaluate the biomechanical influences of self-drilling and self-tapping methods on orthodontic micro-implants under immediate loading.

Methods: Fifty-six micro-implants placed at the interradicular areas of buccal side of upper and lower jaws in two dogs were divided into self-drilling and self-tapping groups. A horizontal load of 1.96 N was immediately given for 9 weeks. Peak insertion torque and peak removal torque were tested immediately after implantation and after the dogs were killed, respectively.

Results: Both in the upper and lower jaws peak insertion torque was significantly higher in self-drilling group [(5.6 +/- 1.1) N.cm and (8.7 +/- 2.3) N.cm] than in self-tapping group [(3.5 +/- 2.1) N.cm and (7.4 +/- 1.1) N.cm] (P < 0.05). Both in the upper and lower jaws peak removal torque was higher in self-drilling group [(-6.5 +/- 2.2) N.cm and (-7.1 +/- 2.0) N.cm] than in self-tapping group [(-5.7 +/- 2.3) N.cm and (-6.1 +/- 0.5) N.cm]. No significant difference was found (P > 0.05). The tendency of fracture was found in self-drilling group.

Conclusions: Self-drilling micro-implants have high initial stability and can be used in the maxilla and at thin cortical bone area of mandible.