Korean J Orthod.  2011 Oct;41(5):337-345. 10.4041/kjod.2011.41.5.337.

Effect of friction from differing vertical bracket placement on the force and moment of NiTi wires

• Park JB
• Yoo JA
• Mo SS
• Choi KC
• Kim YJ
• Han SH
• Kook YA

• KMID: 1975389
• DOI: http://doi.org/10.4041/kjod.2011.41.5.337

Abstract

OBJECTIVE
The purpose of this study was to evaluate the effect of force and moment produced by Nickel-titanium wires of different sizes at activation and deactivation according to differing vertical bracket displacement.
METHODS
Superelastic NiTi wires of 3 different sizes (0.014", 0.016", and 0.016" x 0.022") were tied with elastomeric or 0.009-inch stainless steel ligations in a twin-bracket, 0.018-inch slot. A testing machine recorded the effects of simulated activation of 5 distances from 1 to 5 mm and deactivation of 5 distances from 4 to 0 mm, in increments of 1 mm.
RESULTS
Frictional force increased the wire stiffness during loading. Ligation of 0.014-inch NiTi wire with O-ring resulted in a significant increase in the stiffness. On application of orthodontic force for 5 mm of vertical displacement of teeth, the effective displacement in the case of the 0.014", 0.016", and 0.016" x 0.022" NiTi wires was 2 mm, 3 mm, and 4 mm, respectively.
CONCLUSIONS
Our results showed that movement of teeth with large vertical displacement was ineffective because of excessive friction. This finding might contribute to the understanding of the force system required for effective teeth movement and thereby facilitate the application of the appropriate light wire for leveling and alignment.

Keyword

Stainless steel ligation; Force & moment; Friction; Vertical displacement

MeSH Terms

Displacement (Psychology)
Elastomers
Friction
Ligation
Light
Polymers
Stainless Steel
Tooth
Elastomers
Polymers
Stainless Steel

Figure

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  Fig. 1 Each sensor was bonded with a bracket, and wire was applied passively. The position of each sensor was then adjusted precisely, setting the initial force and moment to 0.

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  Fig. 2 Force system at bracket/wire interface. Moment in clockwise direction (+). Force in right and upward direction (+). A, Bracket located in the middle for displacement; B, laterally positioned bracket connected to sensor. Fav, Vertical force measured on bracket A (signal +: ↑); Fbh, horizontal force measured on bracket B (signal +: →); Mb, moment measured on bracket B (signal +: ↷).

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  Fig. 3 Moment difference between theoretical and practical values of three NiTi wires tied with stainless steel ligation.

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  Fig. 4 Moment difference between theoretical and practical values of three NiTi wires tied with O-ring.

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  Fig. 5 Theoretical value of 0.014" NiTi and 0.016" × 0.022" NiTi wire tied with stainless steel ligation.

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  Fig. 6 Theoretical value of 0.014" NiTi and 0.016" × 0.022" NiTi wire tied with O-ring.

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