A photoelastic study on the initial stress distribution of the molar anchoring spring(MAS) during retraction of the maxillary canine.
- Author:
Youn Sic CHUN
1
Author Information
1. Division of Orthodontics, Department of Dentistry, College of Medicine, Ewha Womans University, Korea.
- Publication Type:Original Article
- Keywords:
Molar Anchoring Spring(MAS);
NiTi closed coil spring;
sliding mechanics;
tip-back bend
- MeSH:
Bicuspid;
Mechanics;
Molar*
- From:Korean Journal of Orthodontics
1996;26(4):341-348
- CountryRepublic of Korea
- Language:Korean
-
Abstract:
The efficiency of maxillary canine retraction by means of sliding mechanics along an 0.016 continuous labial arch and an 0.009 inch in diameter with a lumen of 0.030 inch NiTi closed coil spring was compared with that using the same NiTi closed coil spring and Molar Anchoring Spring(MAS) which was designed by author. MAS was made of .017" X .025" TMA wire and was given 60 degree tip-back bend on the wire close to the molar tube. This study was designed to investigate molar and canine root control during retraction into an extraction site with continuous arch wire system. Two techniques were tested with a continuous arch model embedded in a photoelastic resin. A photoelastic model was employed to visualize the effects of forces applied to canine and molar by two retraction mechanics. With the aid of polarized light, stresses were viewed as colored fringes. The photoelastic overview of the upper right quadrant showed that stress concentrations were observed in its photoelastic model. The obtained results were as follows. 1. Higher concentration of compression can be seen clearly at the distal curvature of the canine and mesial curvature of the molar and premolar when NiTi closed coil spring was applied only, which means severe anchorage loss of the molar and uncontrolled tipping of the canine. 2. The least level compression was presented at the mesial root area of the molar and premolar, and mesial root area of the canine when NiTi closed coil spring and MAS were used simultaneously. Especially mesial alveolar crest region of the canine was shown moderate level of compression that means MAS can be used as a appliance for anchorage control and prevention of canine extrusion and uncontrolled tipping during canine retraction.
