title: Effects of wobbling angle on the stability measures of orthodontic mini-implants during insertion and removal procedures.
abstract: OBJECTIVE
  To investigate the effects of wobbling angle on the stability measures of orthodontic mini-implants (OMIs) during insertion and removal procedures in artificial bone blocks.
  
  
  METHODS
  A total of 36 OMIs (self-drilling type, cylindrical shape, 7 mm in length, 1.45 mm in diameter) were allocated into three groups according to the amount of wobbling angle (W-0°, W-2°, and W-4° groups; N = 12 per group). The OMIs were installed and subsequently removed from artificial bone blocks (Sawbone) using a driving torque tester with a uniform speed of 28 rpm. Insertion peak time (IPT), maximum insertion torque (MIT), total insertion energy (TIE), near-peak insertion energy (NPIE), maximum removal torque (MRT), and near-peak removal energy (NPRE) were measured.
  
  
  RESULTS
  The W-4° group showed the longest IPT and highest TIE and NPIE, followed by the W-2° and W-0° groups (W-0° < W-2° < W-4°, all P < .001). The W-2° and W-4° groups showed significant increase in MIT compared with the W-0° group (W-0° < [W-4°,W-2°]; P < .001). Although there was no significant difference in NPRE among the three groups, the W-4° group showed a decrease in MRT compared with the W-0° and W-2° groups (W-4° < {W-2°,W-0°]; P < .05). Although the W-4° group showed a 14.5% (2.9 Ncm) increase in MIT compared with the W-0° group, there was only a 6% (1.3 Ncm) decrease in MRT from the W-0° group to the W-4° group.
  
  
  CONCLUSIONS
  Slight wobbling during the OMI insertion procedure may be acceptable in terms of the stability measures of OMIs during insertion and removal procedures.
authors.affiliation: a  Clinical Assistant Professor, Department of Dentistry, Korea University Guro Hospital, and PhD graduate student, Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, South Korea.
authors.forename: Il-Sik
authors.initials: IS
authors.lastname: Cho
authors.forename: Sang-Ho
authors.initials: SH
authors.lastname: Baek
authors.forename: Young Ho
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000704:Analysis of Variance; D018786:Bone Substitutes; D015921:Dental Implants; D003799:Dental Stress Analysis; D008422:Materials Testing / Q000295:instrumentation; D052280:Orthodontic Anchorage Procedures / Q000379:methods*; D011140:Polyurethanes; D013314:Stress, Mechanical; D019415:Torque
chemical_list: D018786:Bone Substitutes; D015921:Dental Implants; D011140:Polyurethanes