Korean J Orthod.  2006 Aug;36(4):275-283.

Effect of dual pitch mini-implant design and diameter of an orthodontic mini-implant on the insertion and removal torque

• Kim JW
• Cho IS
• Lee SJ
• Kim TW
• Chang YI

Abstract

OBJECTIVE
Small orthodontic mini-implants are useful as anchorage. However they have some weaknesses such as loosening. This study was carried out to analyze the mechanical effects of the dual pitch and diameter on the insertion and removal torque of mini-implants.
METHODS
The threads of mini-implants were mono and dual pitch. The diameters of mini-implants were 1.4 mm and 1.6 mm. Four groups were tested (mono 1.4 mm, mono 1.6 mm, dual 1.4 mm and dual 1.6 mm). All were inserted and removed on polyurethane foam with the torques being measured.
RESULTS
The maximum torque of the dual pitch groups was higher than the mono pitch groups during removal but lower during insertion. The maximum torque of the 1.6 mm diameter groups was higher than the 1.4 mm diameter groups during insertion and removal. The dual pitch 1.4 mm group showed the lowest insertion torque but had similar or superior levels of removal torque to that of the mono pitch 1.6 mm group.
CONCLUSIONS
The dual pitch especially showed a continuous high removal torque after the peak. Despite the small diameter, the dual pitch might improve the initial mechanical stability.

Keyword

Orthodontic mini-implant; Stability; Dual pitch; Diameter

MeSH Terms

Polyurethanes
Torque*
Polyurethanes