American Journal of Orthodontics and Dentofacial Orthopedics
Original ArticleEffect of archwire size and material on the resistance to sliding of self-ligating brackets with second-order angulation in the dry state*,**,*,**,*
Section snippets
Material and dimensions
Of the 4 types of 22-mil upper left premolar self-ligating brackets (Table I), 1 bracket design (Damon 2) had a slide, and 3 had clips (In-Ovation, SPEED, and Time) (Fig 2).The Damon 2 and the SPEED brackets had prescriptions of −7° torque
Results
When paired with 4 different self-ligating bracket designs, the RS values of 3 different archwire sizes and 3 different archwire materials were compared after tipping at various degrees of second-order angulation.
Dimensions of archwires and brackets
For the brackets with clips, the heights (Y) of the slots (Fig 3, bottom) changed from 1 wall of the slot to the other (Fig 2). At a distance (X) equal to the SIZE of the archwire, Y was estimated by solving the equation, Y = MX + B, that describes the lumen. If the HEIGHT of the archwire was greater than the estimated Y value, the deflection of the slide or the clip was estimated by subtracting Y from the HEIGHT (Table V, last column). The 14-mil NiTi A archwires were not predicted to deflect
Conclusions
When clearance existed between the archwire and the walls of the bracket's slot, the ligation force applied by the slide or the clip to the archwire was estimated by dividing the measured resistance to sliding by the coefficient of friction (which depended on the materials of the archwire-bracket couple). When brackets with slides were used, no ligation force was produced, but, when brackets with clips were used, the amount of ligation force appeared proportional to the dimensions of the
Acknowledgements
The authors appreciate the generous donation of the materials by 3M/Unitek, American Orthodontics, Dentaurum, Forestadent USA, GAC International, RMO, Strite Industries Limited, and Sybron Dental Supply Ormco.
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aDepartment of Biomedical Engineering.
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bDepartment of Orthodontics.
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cDental Research Center.
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dCurriculum in Applied and Materials Science.
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