Korean J Orthod.  2014 Jul;44(4):177-183. 10.4041/kjod.2014.44.4.177.

Geometrical design characteristics of orthodontic mini-implants predicting maximum insertion torque

• Katic V
• Kamenar E
• Blazevic D
• Spalj S

• KMID: 2273274
• DOI: http://doi.org/10.4041/kjod.2014.44.4.177

Abstract

OBJECTIVE
To determine the unique contribution of geometrical design characteristics of orthodontic mini-implants on maximum insertion torque while controlling for the influence of cortical bone thickness.
METHODS
Total number of 100 cylindrical orthodontic mini-implants was used. Geometrical design characteristics of ten specimens of ten types of cylindrical self-drilling orthodontic mini-implants (Ortho Easy(R), Aarhus, and Dual Top(TM)) with diameters ranging from 1.4 to 2.0 mm and lengths of 6 and 8 mm were measured. Maximum insertion torque was recorded during manual insertion of mini-implants into bone samples. Cortical bone thickness was measured. Retrieved data were analyzed in a multiple regression model.
RESULTS
Significant predictors for higher maximum insertion torque included larger outer diameter of implant, higher lead angle of thread, and thicker cortical bone, and their unique contribution to maximum insertion torque was 12.3%, 10.7%, and 24.7%, respectively.
CONCLUSIONS
The maximum insertion torque values are best controlled by choosing an implant diameter and lead angle according to the assessed thickness of cortical bone.

Keyword

Orthodontic mini-implant; Mini-implant stability; Mini-implant orthodontic anchorage; Implant insertion torque

MeSH Terms

Torque*

Figure

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  Figure 1 Orthodontic mini-implant with handheld screwdriver.

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  Figure 2 Tested mini-implants (from left to right): Dual Top™ (Jeil Medical Corp., Seoul, Korea) 1.4 × 6 mm, and 1.4 × 8 mm; Aarhus (MEDICON eG, Tuttlingen, Germany) 1.5 × 6 mm, and 1.5 × 8 mm; Dual Top™ 1.6 × 6 mm, and 1.6 × 8 mm; Ortho Easy® (FORESTADENT®, Pforzheim, Germany) 1.7 × 6 mm, and 1.7 × 8 mm; Dual Top™ 2.0 × 6 mm, and 2.0 × 8 mm.

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  Figure 3 Geometrical design characteristics of mini-implants (length [a], outer diameter [b], depth [c], pitch [d], and lead angle [e] of the thread).

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  Figure 4 Torque-measuring device with mounted bone sample.

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  Figure 5 Representative curve for manual insertion of orthodontic mini-implants.

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