Affordable Access

Publisher Website

Load system of segmental T-loops for canine retraction

Authors
Journal
American Journal of Orthodontics and Dentofacial Orthopedics
0889-5406
Publisher
Elsevier
Volume
144
Issue
4
Identifiers
DOI: 10.1016/j.ajodo.2013.05.007
Disciplines
  • Design

Abstract

Introduction The orthodontic load system, especially ideal moment-to-force ratios, is the commonly used design parameter of segmental T-loops for canine retraction. However, the load system, including moment-to-force ratios, can be affected by the changes in canine angulations and interbracket distances. We hypothesized that clinical changes in canine position and angulation during canine retraction will significantly affect the load system delivered to the tooth. Methods The load systems of 2 T-loop groups, one for translation and the other for controlled tipping, from 9 bilateral canine retraction patients were made to the targeted values obtained from finite element analyses and validated. Each loop was tested on the corresponding maxillary dental cast obtained in the clinic. The casts were made before and after each treatment interval so that both initial and residual load systems could be obtained. The pretreatment and posttreatment interbracket distances were recorded for calculating interbracket distance changes. Results As the interbracket distances decreased, the average retraction-force drop per interbracket distance reduction was 36 cN/mm, a 30% drop per 1 mm of interbracket distance decrease. The average antitipping-moment drops per interbracket distance reductions were 0.02 N-mm per millimeter for controlled tipping and 1.4 N-mm per millimeter for translation, about 0.6% and 17% drops per 1 mm of interbracket decrease, respectively. Consequently, the average moment-to-force ratio increases per 1 mm of interbracket distance reduction were 1.24 mm per millimeter for controlled tipping and 6.34 mm per millimeter for translation. There was a significant residual load, which could continue to move the tooth if the patient missed the next-scheduled appointment. Conclusions Clinical changes in canine position and angulation during canine retraction significantly affect the load system. The initial planned moment-to-force ratio needs to be lower to reach the expected average ideal value. Patients should be required to follow the office visit schedule closely to prevent negative effects because of significant moment-to-force ratios increases with time.

There are no comments yet on this publication. Be the first to share your thoughts.

Statistics

Seen <100 times
0 Comments

More articles like this

On the use of vertical loops in retraction systems...

on American Journal of Orthodonti... April 1991

Canine retraction: a comparison of two preadjusted...

on American Journal of Orthodonti... August 1996

Effects of the zygoma anchorage system on canine r...

on European journal of orthodonti... October 2010

Canine retraction: A comparison of two preadjusted...

on American Journal of Orthodonti... Jan 01, 1996
More articles like this..