Korean J Orthod.  2008 Feb;38(1):5-12. 10.4041/kjod.2008.38.1.5.

Insertion and removal torques according to orthodontic mini-screw design

• Cha JY
• Yoon TM
• Hwang CJ

• KMID: 1481501
• DOI: http://doi.org/10.4041/kjod.2008.38.1.5

Abstract

OBJECTIVE
This study was designed to analyze the primary and secondary stability characteristics of orthodontic mini-screws of tapered design when compared with the cylinder mini-screw.
METHODS
A total of 48 mini-screws were placed into the buccal alveolar bone of the mandible in 6 male beagle dogs. Comparison was made between tapered and cylinder type mini-screws (Biomaterials Korea, Seoul, Korea). Maximum insertion torque (MIT) was measured using a torque sensor (Mark-10, MGT 50, USA) during installation, and maximum removal torque (MRT) was recorded after 3 and 12 weeks of loading.
RESULTS
Taper mini-screws showed a higher MIT value of 22.3 Ncm compared with cylinder mini-screw showing 13.6 Ncm (p < 0.001). The MRT of the taper mini-screw showed a significantly higher value of 9.1 Ncm than those of cylinder mini-screw of 5.7 Ncm at 3-weeks after installation (p < 0.05). However, there was no difference in the MRT value between the taper and cylinder mini-screws at 12 weeks of loading.
CONCLUSIONS
These results showed that the high insertion torque of the taper mini-screw design increases initial stability until 3 weeks of loading, but does not have any effect on the secondary stability at 12 weeks of loading.

Keyword

Orthodontic mini-screw; Insertion torque; Removal torque

MeSH Terms

Animals
Dogs
Humans
Korea
Male
Mandible
Torque