• 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.

• The korean journal of orthodontics
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• v.18 no.1 s.25
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• pp.25-53
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• 1988

Retraction of canines represents a fundamental stage in a considerable number of orthodontic treatment. Correct position of the canine after retraction is most important for function, stability, and esthetics. The purpose of this study was to investigate the stress in the periodontal tissue at the initial phase during canine retraction using various types of sectional retraction springs, by finite element method. Three dimensional model of tooth, periodontal ligament, bone and eight springs were simulated and tested. The following results were obtained. 1. In sectional retraction springs, increasing number of helix and the closed loop in preference to the open loop provided an decrease in horizontal force. Without angulating the arms of spring, the T-loop revealed the highest Moment-to-force ratio. 2. The Moment-to-force ratio raised by angulating mesial and distal arms of spring, but very large horizontal force was applied to canine. 3. When optimal force and optimal moment was applied to canine, the stress induced was homogeneous and the difference of stress value from cervix to the apex was little.

• 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.28 no.2 s.67
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• pp.269-276
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• 1998

In maxillary canine retraction by means of sliding mechanics, we designed MAS(molar anchoring spring) to prevent anchorage loss and uncontrolled tipping of tooth movement and have applied it in clinical cases. The anchorage control of the maxillary first molar and type of tooth movement of the maxillary canine were studied in 31 subjects. The measurements were made on cephalograms, orthopantomograms and dental casts. The obtained results were as follows. 1. In case of the maxillary first molar, there was a little sagittal anchorage loss, but there was no vertical & transverse anchorage loss. 2. In case of the maxillary canine, there was distal tipping movement and also there was a little intrusion tendency.

• The korean journal of orthodontics
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• v.29 no.5 s.76
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• pp.511-519
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• 1999

The shape of orthodontic retraction spring was varied and force system of each case was obtained using numerical analysis and verified with spring tester. The factors for obtaining biomechanically efficient spring under anatomic limitation were suggested as follows. 1. M/F ratio increases and L/D rate decreases as loop height increases. 2. M/F ratio increases and L/D rate decreases as incorporating more wire above minimum bending moment area. 3. M/F ratio decreases and L/D rate decrease as incorporating more wire below minimum bending moment area. 4. M/F ratio can not be greater than spring height no matter how much wire is incorporated at the apex of the loop. 5. Additional moment is necessary to obtain enough M/F ratio for translation under anatomical limitation. 6. Additional moment should be incorporated at every pah of the spring because M/F ratio and L/D rate decreases as horizontal spring length increases. 7. Material, cross section, and shape of the spring influence L/D rate, whereas M/F ratio is influenced by the shape of the spring independent from material and cross section.

• The korean journal of orthodontics
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• v.29 no.5 s.76
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• pp.521-534
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• 1999

The purpose of this study was to find the difference of stress distribution on canine altered by the application point of preangulated T-loop spring. For this study, the finite element models of upper left canine, upper left second premolar and upper left first molar were made. Also, the finite element models of $0.017{\times}0.025$ inch preangulated, preactivated T-loop spring and $0.018{\times}0.025$ inch stainless steel wire were made. Three types of T-loop spring were made . the middle of activated T-loop is positioned in accordance with the middle position of distance of bracket position of both the canine and first molar, 2mm anterior, 2mm posterior. We compared the forces and the distribution of stress that were generated by the difference of position of T-loop spring. The results were as follows. 1. All of the 3 types of T-loop spring showed the similar retraction forces. 2. All showed the similar amount & pattern of stress distribution. 3. The centers of rotation of canine in 3 types of T-loop spring were same and were positioned between C and D plane. 4. The canine showed the intrusive force by 2mm anterior positioned T-loop spring, but the extrusive force by 2mm posterior positioned T-loop suing. Neverthless, because of the small amount of the forces, the effect of vertical force was not significant.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.263-271
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• 1995

The purpose of this study nab to evlauate and compare the effect of the variable factors of wire on the elastic properties of looped rectangular wire. Five variable factors were presented-material(Hi-T, blue Elgiloy), wire size(.016'$\;\times\;$.022', .018'$\;\times\;$.025'), loop length(15mm, 20mm), loop configuration(open loop, closed loop), gabling (non-gable, gable). So, the total 256 specimens were divided into 32 groups, and each of those nab pulled on Instron testing machine. The load-deflection curve of each wire obtained, from which force, range in elastic limit, and stiffness were computed and analyzed statistically. The results were obtained as follows : 1. All of the variable factors - wire material, size, loop length loop configuration, and gabling - took a significant effect on load-deflection rate of looped wire. 2. The force at elastic limit was the smallest in the group of Hi-T, .016'$\;\times\;$.022', 20mm loop length, open loop, non-gable, and the largest in the group of blue Elgiloy, .018'$\;\times\;$.025', 15mm loop length, closed loop, non-gable. 3. The range at elastic limit was the smallest in the group of Hi-T, .018'$\;\times\;$.025', 15mm loop length, open loop, non-gable, and the largest in the group of HI-T, .016'$\;\times\;$.022', 20mm loop length, closed loop, gable. 4. Loop configuration and loop length were the most effective factors on the elastic properties of looped wires, and gabling was the least effective.