Journal Article

Initial changes of centres of rotation of the anterior segment in response to horizontal forces

Kwangchul Choy, Kyung-Ho Kim and Charles J. Burstone

in The European Journal of Orthodontics

Published on behalf of European Orthodontics Society

Volume 28, issue 5, pages 471-474
Published in print October 2006 | ISSN: 0141-5387
Published online August 2006 | e-ISSN: 1460-2210 | DOI: http://dx.doi.org/10.1093/ejo/cjl023
Initial changes of centres of rotation of the anterior segment in response to horizontal forces

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This study investigated the changes in the initial centres of rotation (Crot) of the upper six anterior teeth in response to a horizontal load. Six upper anterior teeth were extracted, splinted as a unit, and embedded in dental stone after the roots were uniformly coated with silicone. An aluminium fixture was bonded to the anterior segment and three linear variable differential transformers (LVDTs) were attached to measure the microdisplacement of the segment. A pulley and dead weight assembly were used to apply a 200 g occluso-gingivally varying horizontal force to the segment. The changes in the Crot for the anterior segment to the horizontal load were recorded.

The results showed that the centre of resistance (Cres) of the upper anterior segment was located 14.5 mm apical and 9.5 mm distal from the incisal edge of the central incisors. A linear functional axis (a trace of the measured Crot) was recorded. The functional axis maintained an angle of 14.5 degrees to the vertical axis of the anterior segment passing through the Cres of the segment. The Crot constant, which determines the tipping sensitivity of the segment, was 23 mm2. The results demonstrate that the upper anterior segment may be slightly intruded when a horizontal force is applied and is less prone to tipping than a single tooth.

Journal Article.  2033 words.  Illustrated.

Subjects: Restorative Dentistry and Orthodontics

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