Objective: To investigate the effects of different pilot-drilling methods on the biomechanical stability of self-tapping mini-implant systems at the time of placement in and removal from artificial bone blocks. Methods: Two types of artificial bone blocks (2-mm and 4-mm, 102-pounds per cubic foot [102-PCF] polyurethane foam layered over 100-mm, 40-PCF polyurethane foam) were custom-fabricated. Eight mini-implants were placed using the conventional motor-driven pilot-drilling method and another 8 mini-implants were placed using a novel manual pilot-drilling method (using a manual drill) within each of the 2-mm and 4-mm layered blocks. The maximum torque values at insertion and removal of the mini-implants were measured, and the total energy was calculated. The data were statistically analyzed using linear regression analysis. Results: The maximum insertion torque was similar regardless of block thickness or pilot-drilling method. Regardless of the pilot-drilling method, the maximum removal torque for the 4-mm block was statistically higher than that for the 2-mm block. For a given block, the total energy at both insertion and removal of the mini-implant for the manual pilot-drilling method were statistically higher than those for the motor-driven pilot-drilling method. Further, the total energies at removal for the 2-mm block was higher than that for the 4-mm block, but the energies at insertion were not influenced by the type of bone blocks. Conclusions: During the insertion and removal of mini-implants in artificial bone blocks, the effect of the manual pilot-drilling method on energy usage was similar to that of the conventional, motor-driven pilot-drilling method.

Objectives: To determine a reliable method of drilling a pilot hole when using a self-tapping surface-treated mini-implant and to evaluate stability after placement. Materials and Methods: Implant sites were predrilled in 12 rabbits with two devices: a conventional motor-driven handpiece and a newly developed hand drill. Mini-implants were then inserted in a complete random block design. Samples were divided into 1-week and 6-week groups to investigate osseointegration capacity in relation to the two time intervals. Mechanical and histomorphometric assessments were performed. Results: Mechanical analysis revealed no difference in maximum removal torque or total removal energy between the motor-driven predrilling group and the hand-drilling group. No difference was found between the 1-week group and the 6-week group. Histomorphometric evaluation showed no difference in the bone-implant contact (BIC) ratio or the bone volume (BV) area. For the time interval, a statistically significant increase in BIC and BV area was found in the 6-week group when compared to the 1-week group. Conclusions: The osseointegration potential of the motor-driven predrilling method was not different from that of the manual predrilling method with the newly developed hand drill. Hand drilling may be an attractive predrilling method in preference to the conventional motor-driven pilot drilling. (Angle Orthod. 2012;82:1008-1013