Removal torque of miniscrews used for orthodontic anchorage--a preliminary report.
OBJECTIVE
Implant anchors such as miniscrews and miniplates have been loaded immediately for anchorage during orthodontic treatment. The purpose of this study was to measure the removal torque of immediately loaded miniscrews after clinical usage and to determine the possible factors associated with this value.


METHODS
From 29 patients with malocclusions, 46 miniscrews were removed, and removal torque was measured with a torque gauge. Removal torque values were subjected to statistical analysis for possible association of different clinical characteristics.


RESULTS
The mean removal torque value was 1.10 kg x cm, and removal torques for 50% of the implants were greater than 0.89 kg x cm (8.7 N x cm). Removal torque values were significantly higher in the mandible than in the maxilla. The removal torques of 15-mm and 17-mm miniscrews were significantly higher than those of 13-mm miniscrews. Therefore, the site of implantation and miniscrew length were important factors associated with removal torque. However, there was no significant correlation between the removal torque value and age, gender, healing time, or time in function.


CONCLUSIONS
When miniscrews are used as anchorage for uprighting tipped molars, excessive torque in a counterclockwise direction may loosen them. From the measurements obtained in this investigation, miniscrews can sufficiently sustain an uprighting moment.


CONCLUSIONS
The removal torque values of the majority of miniscrews in this study population when loaded immediately as orthodontic anchorage were greater than 0.89 kg x cm, and this was sufficient for these implants to fulfill their purpose as anchors in 3-dimensional tooth movements.
Chen
Yi-Jane
YJ
Department of Orthodontics, School of Dentistry, College of Medicine, National Taiwan University, Taipei.
Chen
Yuan-Hou
YH
Lin
Li-Deh
LD
Yao
Chung-Chen Jane
CC
D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001863:Bone Screws; D003799:Dental Stress Analysis; D020878:Device Removal; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008904:Miniaturization; D008963:Molar; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D014087:Tooth Movement Techniques / Q000295:instrumentation; D019415:Torque