• The korean journal of orthodontics
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• v.11 no.2
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• pp.71-75
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• 1981

The author has studied on the gonical angles in cephalometric roentgenograph and orthopantomograph. Lateral cephalometric roentgenograms and orthopantomograms were taken from 62 patients who were consisted of 32 boys and 30 girls with dentoalveolar Class I malocclusion. Genial angles were measured on cephalograms and orthopantomograms respectively, and calculated the mean values and standard deviations and 't' test was performed on the relationship between the cephologram and orthopantomogram. Results were as followings; 1. Mean value of genial angles was $126.47^{\circ}\;{\pm}\;5.62$ in cephalgram. In orthopantomograms the gonial angle was $125.23^{\circ}\;{\pm}\;6.68$ in left side and $126.47^{\circ}\;{\pm}\;6.85$ in the right side. 2. Result of 't' test showed no significant differences on the level of 1 percent.

• The korean journal of orthodontics
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• v.11 no.2
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• pp.77-83
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• 1981

The author analyzed the morphological pattern of mandibles and lower third molars in order to study and predict the impaction of the developmental third molars. The subjects consisted of 37 males and 87 females with malocclusion. The following results were obtained: 1. The mandible was shown to be shorter in the impacted third molar group than in the erupted group, both in over-all length and in body length. 2. The developmental mesial angulation of the third molar to the mandibular plane was higher in the impacted third molar group. 3. There was a tendency for impacted third molars to be slightly larger than those which erupted except Class II malocclusion in female. 4. In the available space for the eruption of the third molar, significant space deficiency was found in association with the impacted third molar group compared with the erupted group.

• The korean journal of orthodontics
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• v.11 no.2
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• pp.101-108
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• 1981

This investigation was designed to compare the calcification degree of maxillary second permanent molar to mandibular second permanent molar in skeletal Class III Malocclusion. The material selected for this study consisted in standand lateral cephalogram study model and orthopantomogram of two hundred fifty seven Korean Children, one hundred twenty one boys and one hundred twenty four girls, aged 6 through 12 years, having skeletal Class III Malocclusion. On the basis of findigs of this study, the following results were obtained 1. In the stage of completion of crown, there was no significant difference in calcification degree between maxillary second molar and mandibular second molar of both boys and girls in skeletal Class III Malocclusion. 2. From 8 years of age at the stage of beginning root formation to 12 years of age, the calcification degree of mandibular second molar was more advanced than Maxillary second molar of both boys and girls in skeletal Class III Malocclusion.

• 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.11 no.2
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• pp.125-134
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• 1981

To study the calcification of second molars in skeletal class II malocclusion, the author examined cephalograms, orthopantomograms, periapical films of 391 children from 7y 0m to 15y 11 m years old who had skeletal class II malocclusion, and observed the difference in the calcification stage between upper and lower second molars. The result s are as follows. 1. The mean ages of crown completion of upper and lower second molars are $8.7{\pm}1.75$, $8.8{\pm}1.13$ in boys, and $8.4{\pm}0.81$, $8.5{\pm}0.91$ in girls. 2. The mean ages of root completion of upper and lower second molars are $14.0{\pm}1.09,\;14.5{\pm}0.52$ in boys, and $13.7{\pm}1.15,\;13.8{\pm}1.18$ in girls. 3. The calcification stages of upper second molars are more advanced than those of lower second molars at $5\%$ level in both sexes.

• The korean journal of orthodontics
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• v.11 no.2
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• pp.135-142
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• 1981

This study was performed to observe the gross reactions of surrounding maxillary sutures to the widening of midpalatal suture in the dog. Three healthy dog were chosen for the experiment. One animal was used as control, and two were used as experimental animals. Midpalatal suture was expanded total 7mm with screw for 10 days. The following results were obtained : 1. Midpalatal suture was expanded with the most width, in which anterior was be more expanded than the posterior, and shape was wedge form. 2. Interincisive suture was definitely expanded. 3. Internasal suture and interfrontal suture were slightly expanded. 4. Expansion of frontomaxillary suture, frontoparietal suture, frontonasal suture, zygomatico temporal suture, zygomatico frontal suture, zygomatico maxillary suture, occipito mastoid suture, occipito parietal suture, naso incisive suture, naso maxillary suture, and incisive maxillary suture were not observed.

• 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.16 no.1
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• pp.145-154
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• 1986

The purpose of the present study was to investigate the coordination and correlation of growth pattern between craniomaxillary complex and mandible, and among the craniofacial region, body-weight and stature. 14 boys and 16 girls between 6 and 12 years of age were used in this study. The result were as follows; 1. Total increments and maximum increment in mandible is higher than in oraniomaxillary complex during given period and no significant sexual difference existed. 2. The annual growth of craniofacial region did not assume an aspect of constant growth, periodically. 3. Craniofacial growth pattern was interrelated with stature more than with body-weight. 4. The growth behavior of body-weight and stature coincided with the growth of craniofacial region or preceded it in time.

• The korean journal of orthodontics
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• v.23 no.1 s.40
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• pp.137-145
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• 1993

Inverted maxillary incisor is that maxillary incisor rotates to the counterclockwise direction. The incisal margin and root apex of the impacted incisor is palpated at the mucobuccal fold near the labial frenum and on the palate among the rugae, respectively. Orthodontists confront ectopically erupting teeth in various locations. In the past, extraction of impacted teeth that deviated from their normal course of eruption had been performed indiscriminately. But, if it has not any clearcut contraindications, effeort should be made to achieve optimal esthetic results by conservative means, combining the skills of oral surgeon and orthodontist. The present report provides an illustration of satisfactory correction of a inverted maxillary incisor with surgical intervention and many springs that correct the tooth axis. This technique provides the clinician with an additional means to avoid unnecessary extraction of inverted teeth in certain cases.

• The korean journal of orthodontics
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• v.23 no.1 s.40
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• pp.57-74
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• 1993

Anterior crossbite is a common malocclusion in the early deciduous dentition. Even today, many these malocclusion patients are not treated until the mixed or permanent dentition. And the purpose here is to emphasize the need for early diagnosis and possible treatment for these anterior crossbite malocclusions and their associated facial patterns. Case histories of 4 patients selected from the author's practice are presented. Different methods of treatment are evaluated. Some improvement was achieved in all patients from an early interceptive regimen, although ultimately corrective orthodontic treatment may still be needed in some. It is concluded that early interception of deciduous anterior crossbite malocclusion should by attempted in patients ; there should be no delemma in reaching such a decision. And it is essential for diagnosis and treatment to determine exact variations in growth when some appliance are used, it is recommended that growth-related records be made as early as possible.