Comparative study of the primary stability of self-drilling and self-tapping orthodontic miniscrews

The purpose of this study was to determine the influence of self-tapping and self-drilling placement techniques on the stability of miniscrews. Methods: We included 70 orthodontic patients who received miniscrews (140 screws). Miniscrews measuring 1.6 mm in diameter and 8 mm in length were placed using the self-tapping (35 patients, 70 screws) and self-drilling (35 patients, 70 screws) methods. We examined the success rates, placement torque values, Periotest (Medizintechnik Gulden, Bensheim, Germany) values, rates of root contact, and influence of root contact on mobility. Cone-beam computed tomography was used to evaluate root contact. Miniscrews that endured an orthodontic force for 6 months or more were considered successful. Results: The success rates of the miniscrews were approximately 96% with either placement technique. The placement torques were 7 and 7.5 N cm in the self-tapping and self-drilling miniscrews, respectively (P >0.05). The Periotest values of the self-drilling method were significantly greater than those of the self-tapping method. The Periotest values of the self-drilling miniscrews with root contact were significantly greater than those with no root contact. Conclusions: Both placement techniques showed high stability in the maxillary bone, although the self-drilling miniscrews with root contact had greater mobility. Special attention to root contact further improves the stability of the self-drilling miniscrews.