• The korean journal of orthodontics
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• v.35 no.5 s.112
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• pp.371-380
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• 2005

The purpose of this experimental study was to evaluate aㅜd compare maxillary arch dimensional and positional changes between first and second premolar extraction groups. The Calorific Machine was used to illustrate tooth movement in three dimensions. The experimental teeth except the first or second premolars were embedded in artifical alveolar bone. The extraction space was closed using arch wires with bull loops into which 15 degree gable bends were placed. Before and after space closure, radiographs were taken in the sagittal and occlusal directions using occlusal films. The results showed greater mean maxillary incisor retraction and less anchorage loss in the maxillary first premolar extraction group than in the maxillary second premolar extraction group. Mesiopalatal rotation of anchor teeth was greater after extraction of a maxillary second premolar than a maxillary first premolar (P<.001).

• The korean journal of orthodontics
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• v.50 no.3
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• pp.170-180
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• 2020

Objective: To compare short- and long-term dentoalveolar, skeletal, and rotational changes evaluated by Björk's structural method of superimposition between children with Class II malocclusion treated by functional appliances and untreated matched controls. Methods: Seventy-nine prepubertal or pubertal children (mean age, 11.57 ± 1.40 years) with Class II malocclusion were included. Thirty-four children were treated using an activator with a high-pull headgear (Z-activator), while 28 were treated using an activator without a headgear (E-activator). Seventeen untreated children were included as controls. Lateral cephalograms were obtained before treatment (T1), after functional appliance treatment (T2), and after retention in the postpubertal phase (T3). Changes from T1 to T2 and T1 to T3 were compared between the treated groups and control group using multiple linear regression analysis. Results: Relative to the findings in the control group at T2, the sagittal jaw relationship (subspinale-nasion-pogonion, p < 0.001), maxillary prognathism (sella-nasion-subspinale, p < 0.05), and condylar growth (p < 0.001) exhibited significant improvements in the Z- and E-activator groups, which also showed a significantly increased maxillary incisor retraction (p < 0.001) and decreased overjet (p < 0.001). Only the E-activator group exhibited significant backward rotation of the maxilla at T2 (p < 0.01). The improvements in the sagittal jaw relationship (p < 0.01) and dental relationship (p < 0.001) remained significant at T3. Condylar growth and jaw rotations were not significant at T3. Conclusions: Functional appliance treatment in children with Class II malocclusion can significantly improve the sagittal jaw relationship and dental relationships in the long term.

• The korean journal of orthodontics
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• v.23 no.2 s.41
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• pp.217-227
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• 1993

Preadjusted appliance, following the original concept of the Andrews Straight-Wire appliance, became increasingly common in the 1980s. In six phases of treatment, anchorage control, leveling and aligning, overbite control, overjet reduction, space closure, and finishing are very effective with using the preadjusted appliances. Space closure is the phase of treatment in which the difference between standard edgewise and preadjusted mechanics is most noticeable. Orthodontists have been able to reduce the use of closing loops and, because of the level slot lineup, enjoy the advantages of sliding mechanics. In 1990, Dr. John C. Bennett and Richard P. McLaughlin introduced the new space closure system, namely, elastic 'tiebacks'. They found an $.019'\times.025'$ working archwire most effective in an .022'-slot system. Hooks of .024' stainless steel or .028' brass wire are soldered to the upper and lower archwires. The force required for space closure is delivered by elastic 'tiebacks'. An elastic modulo stretched by 2-3mm(to twice its normal length) usually delivers 0.5-1.5mm of space closure per month. Group movement and sliding mechanics are combined for gentle, controlled space closure, so that about 0.5mm of incisor retraction and 0.5mm of mesial molar movement can be seen each month. The tiebacks are replaced every four to six weeks. By using the elastic 'tiebacks', the next two cases were treated during space closure. Even though we found some clinical problems of this mechanics, long treatment time, hard to control of vertical dimension and anchorage, the application method of this system is so simple that orthodontists can manage many patients during short chair time. But we must apply this mechanics after perfect understanding of the biomechanics in tooth movement.

• The korean journal of orthodontics
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• v.31 no.1 s.84
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• pp.1-13
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• 2001

The extraction lot orthodontic treatment can be adopted for aligning crowded dentition, improving facial esthetics and solving a skeletal discrepancy as alternative for a surgical option. Mandibular second premolar extraction was often selected as treatment plan when there we very little or no space shortage in lower arch or limited retraction of the lower incisors was required. The primary object of this study was evaluate a pretreatment condition and examine the amount of tooth movement ior a mandibular second premolar extraction in growing patients. Pretreatment and posttreatment lateral cephalograms of 14 cases that had their four first premolar extracted (4/4 group), 15 cases with upper first and lower second premolar extraction (4/5 group) were selected. Structural method superimposition was conducted to evaluate a difference of dental change between 4/4 and 4/5 group. The results were as follows, 1. Pretreatment factor for 4/4 extraction or 4/5 extraction choice included maxillary incisor axis to occlusal plane, Class II molar relationship, IMPA and interincisal angle. 2. The amount of molar anterior movement in 4/5 group was greater than that of 4/4 group(p<0.05). 3. There was no significant difference between 4/4 group and 4/5 group in aspects of maxillary tooth movement(p<0.05).

• The korean journal of orthodontics
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• v.33 no.5 s.100
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• pp.339-350
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• 2003

The purpose of this study was to investigate the micro-implant height and anterior hook height to prevent maxillary six anterior teeth from lingual tipping and extruding during space closure. We manufactured maxillary dental arch form, bracket and wire, using the computer aided three-dimensional finite element method. Bracket was $.022'{\times}.028'$ slot size and attached to tooth surface. Wire was $.019'{\times}.025'$ stainless steel and $.032'{\times}.032'$ stainless steel hook was attached to wire between lateral incisor and canine. Length of hook was 8mm and force application points were marked at intervals of In. Four micro-implants were implanted on alveolar bone between second premolar and first molar. The heights of them were 4, 6, 8, 10mm starting from wire. We analyzed initial displacement of teeth by various force application point applying force of 150gm to each micro-implant and anterior hook. The conclusions of 4his study are as the following : 1. When the micro-implant height was 4m and the anterior hook height was 5mm and below, anterior teeth were tipped lingually. When the anterior hook height was 6mm and above, anterior teeth were tipped labially. 2. When the micro-implant height was 6mm and the anterior hook height was 6mm and below, the anterior teeth were tipped lingually. When the anterior hook height was 6m and above, the anterior teeth were tipped labially. But lingual tipping of anterior teeth decreased and labial tipping Increased when the micro-implant height was 6mm, compared with 4mm micro-implant height. 3. When the micro-implant height was 8mm and the anterior hook height was 2mm, the anterior teeth were tipped lingually. When the anterior hook height was 3mm and above, labial tipping movement of the anterior teeth increased proportionally. 4. When the micro-implant height was 10mm and the anterior hook height was 2mm and above, labial tipping of the anterior teeth increased proportionally. 5. As the anterior hook height increased, aterior teeth were tipped more labially. But extrusion occurred on canine and premolar area because of the increase of wire distortion. 6. Movement of the posterior teeth was tipped distally during maxillary six anterior teeth retraction using micro-im plant because of the friction between bracket and were Based on the results of this study, we could predict the pattern of the tooth movement according to position of micro-implant and height of anterior hook. It seems that we can find the force application point for proper tooth movement in consideration of inclination of anterior anterior teeth, periodontal condition, overjet and overbite

• The korean journal of orthodontics
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• v.28 no.5 s.70
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• pp.825-838
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• 1998

The purpose of this study was to evaluate the differences of soft tissue profile changes between the growing patients and the adult who had passed the growth peak, in orthodontic treatment with four premolar extractions. The results which was taken by correlating the soft tissue changes with hard tissue changes, lip thickness, molar relationship and arch length discrepancy in both groups was like the followings. 1. Significant hard tissue changes were decrease of VIs, VIi, UlPP, LlMP, HIi and increase of HPog'in adults and decrease of VIs, VIi and increase of VA, VPog'and all the vertical measurements in adolescents. 2. Significant soft tissue changes were decrease of VLs, VLi, and VILS in adults and increase of VSn, VSLS, VLs, VPog' and almost all vertical measurements in adolescents, and ${\Delta}LsE,\;{\Denta}LiE$ in adults and ${\Delta}LsE,\;{\Denta}LiE,\;{\Delta}LiSP\;and\;{\Delta}Mang$ was also significant 3. Correlation coefficient between ${\Delta}VIs\;and\;{\Delta}VLs$ was the greatest in adults and the next was ${\Delta}Ii/{\Delta}Li,\;{\Delta}Ii/{\Delta}ILS,\;{\Delta}ID/{\Delta}Li\;and\;{\Delta}ID/{\Delta}ILS$. In contrast all the vertical and horizontal measurements of hard and soft tissue in adolescents showed statistically significant corerrlation. 4. There were differences in correlation between soft tissue changes and incisor inclination and retraction at both groups, but the lower lip, nasolabial angle and mentolabial angle were commonly less influenced by the hard tissue changes in both groups. 5. The thinner the upper lip was, the more the ${\Delta}LsSP$ was in both groups, and the thinner the lower lip was, the more the ${\Delta}LiE\;and\;{\Denta}LiSP$ was in adolescents. 6. Molar relationship didn't influence the soft tissue profile changes. 7. Arch length discrepancy didn't influence the soft tissue profile changes.

• The korean journal of orthodontics
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• v.39 no.5
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• pp.278-288
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• 2009

Objective: The aim of this study was to investigate the changes in the center of resistance of the maxillary teeth in relation to alveolar bone loss. Methods: A finite element model, which included the upper dentition and periodontal ligament, was designed according to the amount of bone loss (0 mm, 2 mm, 4 mm). The teeth in each group were fixed with buccal and lingual arch wires and splint wires. Retraction and intrusion forces of 200 g for 4 and 6 anterior teeth groups and 400 g for the full dentition group were applied. Results: The centers of resistance were at 13.5 mm, 14.5 mm, 15 mm apical and 12 mm, 12 mm, 12.5 mm posterior in the 4 incisor group; 13.5 mm, 14.5 mm, 15 mm apical and 14 mm, 14 mm, 14.5 mm posterior in the 6 anterior teeth group; and 11 mm, 13 mm, 14.5 mm apical and 26.5 mm, 27 mm, 25.5 mm posterior in the full dentition group respectively according to 0 mm, 2 mm, 4 mm bone loss. Conclusions: The center of resistance shifted apically and posteriorly as alveolar bone loss increased in 4 and 6 anterior teeth groups. However, in the full dentition group, the center of resistance shifted apically and anteriorly in the 4 mm bone loss model.