• The korean journal of orthodontics
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• v.24 no.1 s.44
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• pp.87-94
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• 1994

The purpose of this study was to evaluate the torque effect of othodontic wires. Ten types of orthodontic wires (five types of materials, two types of cross-sectional dimensions) were selected. Each group of ire type was constituted with five specimens. These specimens were tested on the universal testing machine(Instron) with specially-designed jig. The torque-twist curve of each wire was obtained and the results were analyzed statistically. The results were as follows. 1. 0.017'$\times$ 0.025' wire showed more torque effect than 0.016'$\times$ 0.022' wire at the same twist. 2.Torque effect was the greatest in stainless steel and the least in Nitinol. 3.The maximum amount of torque was the greatest in heat-treated Blue Elgiloy and the least in Nitinol.

• The korean journal of orthodontics
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• v.22 no.2 s.37
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• pp.475-481
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• 1992

The purpose of this study was to examine the displacement of glenoid fossa during growth, and to investigate the relationship between the displacement of glenoid fossa and mandible. Pretreatment and posttreatment lateral cephalograms of 41 patients (male : 13, female : 28) were obtained from the orthodontic clinics of Wonkwang university hospital and were analized in terms of the position of articulare and mandible and statistically. The obtained results were as follows, 1. Aritculare was displaced posteriorly and inferioly during craniofacial growth and development. 2. The more posteriorly articulare displaced, the less anteriorly pogonion displaced, but the more inferiorly menton displancd. 3. The more posteriorly or inferiorly articulare was located, the more inferiorly menton displaced, and the more posteriorly articulare was located posteriorly, the less cant of the mandibular plane.

• The korean journal of orthodontics
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• v.43 no.3
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• pp.147-158
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• 2013

This article describes the orthodontic treatment of a 31-year-old Korean female patient with gummy smile and crowding. The patient showed excessive gingival display in both the anterior and posterior areas and a large difference in gingival heights between the anterior and posterior teeth in the maxilla. To correct the gummy smile, we elected to intrude the entire maxillary dentition instead of focusing only on the maxillary anterior teeth. Alignment and leveling were performed, and a midpalatal absolute anchorage system as well as a modified lingual arch was designed to achieve posterosuperior movement of the entire upper dentition. The active treatment period was 18 months. The gummy smile and crowding were corrected, and the results were stable at 21 months post-treatment.

• The korean journal of orthodontics
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• v.14 no.2
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• pp.233-239
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• 1984

The author studied on the tongue position, tongue space and intermaxillary space at 4 groups; normal occlusion 30 cases, Angle's Class I bimaxillary protrusion 29 cases, Angle's Class II malocclusion 26 cases, Angle's Class III malocclusion 26 cases. This study used the data from cephalometric films of female subject aged from 16 to 23 years. Following results were obtained; 1. Dorsal height in Angle's Class III malocclusion was greater than normal occlusion. 2. Anterior Intermaxillary Height in Angle's Class I bimaxillary protrusion and Angle's Class III malocclusion was greater than normal occlusion. 3. Tongue space in Angle's Class I bimaxillary protrusion was greater than normal occlusion. 4. The ratio of the tongue space to the intermaxillary space (T.S./I.S.) in Angle's Class II malocclusion was greater and the ratio in Angle's Class III malocclusion is lesser than normal occlusion.

• The korean journal of orthodontics
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• v.14 no.2
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• pp.241-248
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• 1984

The mechanical properties of Cr-Ni alloy of austenitic stainless steel and Co-Cr alloy orthodontic wires were studied in tension. The wires (0.018 inch) were tested in the as-manufactured and heat-treated conditions. Instron type tension testing machine was used for this study. Mean values and standard deviations were computed. The results were as follows; 1. The Cr-Ni orthodontic wires of austenitic stainless steel are generally superior than the Co-Cr orthodontic wires in ultimate tensile strength, In the elongation, however, Co-Cr orthodontic wire are superior than Cr-Ni orthodontic wires. 2. Increase in the degree of strength by heat treatment are more clearly shown in Co-Cr orthodontic wires than Cr-Ni orthodontic wires. And the elongation is decreased by heat treatment in both case. 3. The changes of the degree of strength by cooling method we not clearly shown, but in Cr-Ni orthodontic wires, air cooling are more effective, in Co-Cr orthodontic wires, cooling effect are scarcely shown.

• The korean journal of orthodontics
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• v.19 no.2
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• pp.155-163
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• 1989

Indirect bonding is done by placing the brackets on a model in the laboratory and using a template or tray to transfer the laboratory positioning to the teeth. The advantages of this technique are 1. decreased chair time 2. less patient discomfort 3. accuracy of a attachment placement 4. good adaptation of attachment to tooth contour 5. occlusal relationship of brackets and opposing teeth can be checked The disadvantages of the technique are 1. complex laboratory procedure 2. sometimes difficult on very short clinical crowns 3. teeth with crowns, large buccal restoration will not bond 4. may not be fitted close, if poor adaptation 5. likely to be disturbed setting Several indirect bonding techniques have proved reliable in clinical practice. However, they differ in the way the brackets are attached temporarily to the model, the type of transfer tray or other mechanism used, the adhesive or sealant employed, whether segmented or full bonding used, and the way the transfer is removed so as not to exert excessive force on a still maturing bond.

• The korean journal of orthodontics
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• v.17 no.1
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• pp.85-91
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• 1987

The aim of this study was to clarify whether bonding/debonding procedure will affect the occurance of enamel crack. The frequency of enamel crack was compared between before-bonding and after-debonding on 200 human extracted teeth. Each facial surface of the tooth was divided in 9 fragments. A presence of crack, which was classified by its direction as vertical, horizontal and oblique crack, was surveyed in each fragment. Number of all cracks in facial surface was 1355 at before-bonding, and 1605 at after-debonding, so it revealed significant increase rate of $18.5\%$, but compared by fragment, cracks were significantly Increased in OC, OD, CC and GC fragments. All kinds of cracks were significantly increased, especially increase rate of oblique crack reached $54.9\%$. The increase rate of cracks was not superior at any fragment or region, but some evidence was seen in CC fragment. Judging from the above, increase of crack is unavoidable with bonding/debonding procedures.

• The korean journal of orthodontics
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• v.19 no.2
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• pp.85-93
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• 1989

The purpose of this study was to evalute the corrosion resistance of chemically and thermally recycled metal brackets. In vivo, two types of recycled metal brackets and new brackets were directly bonded for 1 year, and then the microstructure of bracket surface was examined by S.E.M. (J.S.M.-840 Scanning Electron Microscope, Japan). The following results were obtained. 1) The microstructure of new and chemically recycled metal bracket surfaces showed regular structure without island formation and recrystallization; and after 1 year, the same appearance except some scratches. 2) The microstructure of thermally recycled metal bracket surfaces showed a beginning of island formation and recrystallization by annealing, and after 1 year, a typical corrosive appearance, completely island formation with some metal grains by recrystallization. 3) Chemically recycled metal brackets showed better corrosion resistance than thermally recycled metal brackets.

• The korean journal of orthodontics
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• v.17 no.1
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• pp.15-21
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• 1987

The present study was carried out to investigate the relationships between the depth of overbite and the masseteric silent period. Normal subjects of 44 were selected, which consisted of 9 open bites, 24 normal overbites and 11 deep bites, all were 19-29 years of age. EMG activity was recorded on the bilateral masseteric muscles and craniofacial radiography was done. The following results were obtained. 1. The mean duration of masseteric silent period was $18.58{\pm}4.50$ msec in open bite, $17.37{\pm}7.05$ msec in normal overbite and $19.30{\pm}7.62$ msec in deep bite groups. 2. There were no significant differences on masseteric silent period among open bite, normal overbite and deep bite groups. 3. There were no significant correlations between masseteric silent period and craniofacial variables.

• The korean journal of orthodontics
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• v.29 no.1 s.72
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• pp.129-136
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• 1999

Etiologies of the molar teeth impaction are cyst, supernumerary teeth, ankylosis by replacement resorption, abnormal eruptive path, improper orthodontic treatment, etc. If the impacted teeth were untreated, the sequallae was as follows : loss of occlusal function, loss of permanent tooth, extrusion of opposite tooth, root resolution of adjacent teeth. The most important factor of solution of impacted teeth is treatment timing & proper application of orthodontic forces.