title: Are assessments of damping capacity and placement torque useful in estimating root proximity of orthodontic anchor screws?
abstract: BACKGROUND
  Placement torque and damping capacity may increase when the orthodontic anchor screws make contact with an adjacent root. If this is the case, root contact can be inferred from the placement torque and damping capacity. The purpose of this study was to verify the detectability of root proximity of the screws by placement torque and damping capacity. For this purpose, we investigated the relationship among placement torque, damping capacity, and screw-root proximity.
  
  
  METHODS
  The placement torque, damping capacity, and root proximity of 202 screws (diameter, 1.6 mm; length, 8.0 mm) were evaluated in 110 patients (31 male, 79 female; mean age, 21.3 ± 6.9 years). Placement torque was measured using a digital torque tester, damping capacity was measured with a Periotest device (Medizintechnik Gulden, Modautal, Germany), and root contact was judged using cone-beam computed tomography images.
  
  
  RESULTS
  The rate of root contact was 18.3%. Placement torque and damping capacity were 7.8 N·cm and 3.8, respectively. The placement torque of screws with root contact was greater than that of screws with no root contact (P <0.05; effect size, 0.44; power, <0.8). Damping capacity of screws with root contact was significantly greater than that of screws with no root contact (P <0.01; effect size, >0.5; power, >0.95).
  
  
  CONCLUSIONS
  It was suggested that the damping capacity is related to root contact.
authors.affiliation: Associate professor, Department of Orthodontics, Division of Clinical Research, Dental Research Center, School of Dentistry, Nihon University, Tokyo, Japan. Electronic address: motoyoshi.mitsuru@nihon-u.ac.jp.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Motoyoshi
authors.affiliation: Assistant professor, Department of Orthodontics, Division of Clinical Research, Dental Research Center, School of Dentistry, Nihon University, Tokyo, Japan.
authors.forename: Yasuki
authors.initials: Y
authors.lastname: Uchida
authors.affiliation: Senior resident, Department of Orthodontics, School of Dentistry, Nihon University, Tokyo, Japan.
authors.forename: Mizuki
authors.initials: M
authors.lastname: Inaba
authors.affiliation: Assistant professor, Department of Oral and Maxillofacial Radiology, Division of Advanced Dental Treatment, Dental Research Center, School of Dentistry, Nihon University, Tokyo, Japan.
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Ejima
authors.affiliation: Professor and chair, Department of Oral and Maxillofacial Radiology, Division of Advanced Dental Treatment, Dental Research Center, School of Dentistry, Nihon University, Tokyo, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Honda
authors.affiliation: Professor and chair, Department of Orthodontics, Division of Clinical Research, Dental Research Center, School of Dentistry, Nihon University, Tokyo, Japan.
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Shimizu
mesh_terms: D054893:Cone-Beam Computed Tomography; D005260:Female; D006801:Humans; D008297:Male; D052280:Orthodontic Anchorage Procedures; D009967:Orthodontic Appliances; D014092:Tooth Root / Q000000981:diagnostic imaging; D019415:Torque; D055815:Young Adult