Does miniscrew insertion angulation matter?

The use of reduced angle of insertion during miniscrew implant placement has been reported to increase the mechanical retention of miniscrew implants. However, the effects of the insertion angulation in the dentoalveolar bone have not been investigated. Purpose: The purpose of this study was to investigate the effects of insertion angulation on the biomechanical performance of the miniscrew implanted in the dentoalveolar bone. Materials and Methods: 360 self-tapping miniscrew implants (1.6 x 8 mm) (BMK, Seoul, Korea) were systematically inserted in fresh maxillary and mandibular dentoalveolar bone (anterior, middle and posterior area) of minipigs with 30, 60 and 90 degrees to the bone surface aided by a 3-D Surgical Guide (Y&B Products, Chiangmai, Thailand). Maximum insertion torque and pullout strength were assessed with an Imada torque wrench and a Universal Instron Testing Machine, respectively. Results were recorded and analyzed by one-way ANOVA and Pearson correlation coefficients. Results: Maximum insertion torque and pullout strength showed significant correlation (r = 0.81). In the maxilla, no significant difference in the maximum insertion torque and pullout strength was observed between miniscrews implanted with 30, 60 or 90 degrees. Although miniscrews inserted with 30 degrees exhibited highest mechanical performance in the anterior portion of mandible, significant reduced insertion torque and pullout strength values was observed in the middle and posterior areas. No significant difference was observed between miniscrews inserted with 60 and 90 degrees. Conclusions: Insertion angulation did not improve the mechanical performance of miniscrew implanted on the maxillary dentoalveolar bone. Reduced insertion angulation (30 degrees) was only effective on the anterior portion of the mandible. Keywords: miniscrew implants, orthodontics, anchorage, insertion angulation