• The korean journal of orthodontics
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• v.34 no.2 s.103
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• pp.121-129
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• 2004

The purpose of this study was to photoelastically visualize 4he distribution of fortes transmitted to the alveolus and surrounding structures using three different types of headgear for the distal movement of the upper molars. A photoelastic maxillary model was made and three different directional forces applied, which were high-pull, straight-pull, and cervical-pull. Stress distribution was recorded through circular polariscope, and two-dimensional photoelastic stress analysis was performed according to isochromatic fringe characteristics. The results were as follows: 1. In the case of high-pull headgear bodily movement occurred in the medium- length outer bow, stress distribution in the apical region was 1st molar, 2nd premolar, lst premolar in sequence and there was no apparent difference. 2. In the case of straight-pull headgear, bodily movement occurred in the long outer bow and stress distribution in the apical region was heavy in the 1st molar, 2nd premolar, 1st premolar in sequence. But. there were no apparent differences according to the length of the outer bow. 3. In the case of cervical- pull headgear, bodily movement also occulted in 4he long outer bow, and apical stress of the premolar region was heaviest among other cases and apical stress of the 2nd premolar was heaviest in the short outer bow. In clinical situations, to achieve bodily movement of the upper 1st molars without modifying outer bow height, applying an outer bow length as long as the inner bow length in high-pull headgear and applying an outer bow length longer than the inner bow length in straight-pull, cervical-pull headgear are recommended.

• The korean journal of orthodontics
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• v.31 no.2 s.85
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• pp.199-207
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• 2001

The segmented TMA T-loop spring, used for reciprocal space closure and described by Burstone, was used to achievebodily movement of canine. Photoelastic analysis is a technique for the transformation of internal stress into visible light patterns. The two-dimensional photoelastic stress analysis was performed, and stress distribution was recorded by photography. The purpose of this study was to visualize photoelastically the distribution of forces transmitted to the alveolus and surrounding structures using new segmented TMA T-loop spring for canine retraction. The results were as follows: 1. Decreased activation produced decreased stress of upper 1st. premolar extraction site and increased intrusive stress of upper 1st. molar, regardless of T-loop position. 2. At 5mm activation, More posterior positioning of T-loop Produced an increased stress in upper 1st. premolar extraction site. 3. At 3mm activation, More posterior positioning of T-loop produced an increased stress in upper 1st. premolar extraction site and mesial lower half of upper 1st. molar mesio-buccal root. 4. At 1mm activation, More anterior positioning of T-loop produced an increased stress in upper mesial and blew apex area of upper canine root. 5. 0.25 B/L ratio and 3mm activation produced bodily movement of canine. To summarize, desired tooth movement and anchorage requirement is possible by altering the activation and mesio-distal position of the T-loop spring.

• The korean journal of orthodontics
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• v.26 no.4
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• pp.341-348
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• 1996

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.