Abstract
Aims: The present study concerned with the evaluation of the effects of using different bracket,s types (material and design), different arch wire types (shape and size) and different methods of retraction (elastic chain and closed coil spring) on the degree of tipping of canine during its retraction along an arch wire using typodont simulation system (Ormco). Materials and methods: The standardization criteria were all typodont teeth situated in well aligned position, covered and immobilized by the acryl-ic bite except canine, elastic chain and nickel – titanium closed coil spring exerting 180 gm of force on canine measured carefully by tension gauge., the angle between bite plane extension,s bar and canine,s extension bar was (90°) measured by protractor directly on photographs that were taken for typodont using digital camera from both vertical and horizontal direction. Results: The present study showed that sliding the canine on large rectangular arch wire (0.019x0.025 inch) gave rise to a significant de-crease in the degrees of tipping when compared with 0.018 inch and 0.018x0.022 inch arch wires were used. Also, sliding the canine using ceramic brackets (0.022) inch gave rise to the significant decrease in the degree of tipping than when using stainless steel brackets. Another finding of the present study showed that when using elastic chain as a method of retraction gave rise to a a significant decrease in the degree of tipping as compared with nickel – titanium closed coil spring and lastly the attachment of the method of retraction around the bracket tie wing rather than hook gave rise to the high degree of tipping . Conclusion: It was concluded that the canine retraction with 0.019x0.025 inch wire on stan-dard ceramic bracket(0.022)inch by elastic chain retraction method could be regarded as the best com-bination variables that produced less degrees of tipping While the opposite is true for canine retraction with 0.018 inch wire on Roth stain less steel bracket by closed coil spring.
Highlights
Canine retraction is an important biomechanical task in orthodontic treatment
The results of Duncan's Multiple Range test in the present study are listed in Table [1], showed that using nickel – titanium closed coil spring along 0.018 inch wire on the brackets of both stainless steel and ceramic in standard and Roth design gave rise to the highest mean for the degree of tipping, on the other hand using elastic chain that attached to the hook of Roth stainless steel bracket on 0.019x0.025 inch wire gave rise to the lowest one
This result due to many reasons: 1. Arch Wire Size and Shape: Using large rectangular wire gave rise to the lowest mean degree of tipping while Round small wire produces the highest one. This is in agreement with other studies.[18,19,20] Rectangular arch wire usually produces little degree of tipping in comparison with round one, this is in agreement with the findings of Ziegler and Ingervall.[14] the flexural rigidity affects the restoring couple on canine during sliding mechanics as mentioned by Moore and Waters.[21] when light wire was used in sliding mechanics, wire deformation increased and the canine experienced greater tipping.[19] rectangular arch wire offers good control for canine position during sliding, some degree of tipping movement is in veritably occur
Summary
Canine retraction is an important biomechanical task in orthodontic treatment. It is always desired to distalise a canine bodily without tipping it distally or rotating it distopalatally. The morphology of the canine with its long roots and greater buccolingual dimensions, can make this task a challenge.[1] Sliding mechanics offers the advantage of controlling canine rotation.[2, 3] If canine retraction is carried out with no simultaneous tipping or rotation, the subsequent treatment plan will be facilitated and the treatment period can be shortened.[4] Since the elastic chain or (coil spring) is placed at the bracket level and not at the center of resistance. [8] The objectives of this study were: To evaluate and compare the degrees of tipping of canine during sliding mechanics using: 1) different arch wire sizes.2) different bracket types.3) different methods of retraction (elastic chain and closed coil spring, and 4) to evaluate the effect of point of force application The attachments as hook integrated into the bracket, it can be used to shorten the moment arm and thereby decrease the amount of tipping when elastic or springs are used to slide teeth mesiodistaly along an arch wire. [8] The objectives of this study were: To evaluate and compare the degrees of tipping of canine during sliding mechanics using: 1) different arch wire sizes.2) different bracket types.3) different methods of retraction (elastic chain and closed coil spring, and 4) to evaluate the effect of point of force application
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