• Maxillofacial Plastic and Reconstructive Surgery
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• v.33 no.4
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• pp.346-351
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• 2011

Purpose: The purpose of this study was to measure the angular differences between the horizontal reference planes on the CBCT generated PA cephalogram and the modified interpupillary plane, which was usually used in the clinical examination, and to evaluate the validity of the horizontal reference planes. Methods: The CBCT generated PA cephalogram was used to measure the angles between the FH, Lo and IP planes. The subjects consisted of 42 patients with facial asymmetry (males: 21, females: 21, mean-age: 21.6 years). The control groups were also assessed (males: 10, females: 10, mean-age: 23.8 years). The distance of the interpupil was measured on the soft-tissue volume rendered image. The angular differences were statistically analyzed using the $Mann-Whitney$ $U$ $test$ for inter-group comparisons and the $Friedman$ $test$ for intra-group comparisions. Results: The angle between the FH plane and IP plane (the angle of the FH-IP line) showed a statistically significant difference between the two groups ($p$ <0.05). There was no statistical differences between each angle (angle of the FH-IP line, angle of the FH-Lo line, angle of the Lo-IP line) on the intra-group comparision ($p$ >0.05). Conclusion: The angle between the Lo line and IP line (angle of the Lo-IP line) showed no statistically significant difference in both the control and asymmetry groups. Therefore, the Lo line could be used as a horizontal reference plane in CBCT generated PA cephalograms.

• The korean journal of orthodontics
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• v.13 no.1
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• pp.15-30
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• 1983

This study was to investigate the effect of functional pressures of the tongue and lips on the incisor relationship. The incisor relationship was devided into two categories; one is vertical relationship which is subdevided into open bite, normal overbite and deep bite on the basis of overbite, and the other is anteroposterior relationship which is subdevided into cross bite, normal overjet and large overjet on the basis of overjet. The functional tongue and lip pressures exerted to incisors were measured with subminiature pressure sense from the 99 subjects, 19 of normal overbite and overjet, 26 of open bite, 18 of deep bite, 17 of cross bite and 19 of large overjet with age of 17-20, and cephalograms were taken from the same subjects. Functional pressures were analyzed and correlated to craniofacial veriables. The results of present investigation led to the following conclusions. 1. There were no differences in functional and maximum pressures by the tongue and lips exerted to maxillary incisors between normal occlusion, open bite, deep bite, cross bite and large overjet. 2. Significant differences in functional and maximum pressures by the tongue and lips exerted to mandibular incisors have been shown to exist between open bite and deep bite, but no differences between cross bite and large overjet. 3. Equilibrium between tongue pressures and lip pressures did not exist. 4. Significant differences in the ratio of upper functional and maximum pressures to lower pressures of the tongue and lips exerted to upper and lower incisors have been shown to exist between open bite and deep bite, and no differences between cross bite and large overjet. 5, There was significant correlation between functional and maximum pressures exerted to mandibular incisors and craniofacial variables, but not significant correlation between functional and maximum pressures exerted to maxillary incisors and craniofacial variables.

• The korean journal of orthodontics
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• v.13 no.1
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• pp.31-43
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• 1983

The following results were abtained based on the research of the occlusal patterns among 1074 handicapped persons (cerebral palsy: 46, mental subnormality: 619, deafmute: 285, blind: 111, childish autism:8, cleft lip and cleft palate:3, polimyelitis:2) of the age between 6 and 23 in Chollanamdo, Korea, in comparison with a normal group of 1048 children of the age between 6 and 15 selected at random in J primary school in Gwang-ju City. 1. According to Angle's malocclusion classification, all the handicapped groups, except the cerebral palsy and the blind, showed a higher prevalence of malocclusion than that of the normal. Especially the prevalence of Class II, devision 1 malocclusion in the cerebral palsy was the highest, and the prevalence of Class III malocclusion in all the handicapped groups was higher than that of the normal group. Among these groups the highest prevalence of Class III malocclusion was in the Down's syndrome group. 2. On the the abnormal pattern of the anterior region, there was no significant difference $(P\leqq0.05)$ between the normal and the cerebral palsy, the deafmute, and e blind. The open bite $(7.27{\pm}1.04\%)$ and the cross-bite $(32.7{\pm}6.33\%)$ of the Down's syndrome wire higher than that of the normal, and the forward position of the mandible could be recognized in the Down's syndrome group. 3. On the midline position of the dentition, all the handicapped showed the same percentage of deviation, but the degree of mandibular shift to the right $(20.00{\pm}5.39\%)$ or left $(10.91{\pm}4.20\%)$ was higher than that of the normal only in the Down's syndrome group. 4. On the abnormal pattern of the posterior region, the cross-bite of the Down's syndrome was higher than that of the normal by $20.00{\pm}5.39\%$, the cross-bite of the cerebral palsy and the cross-bite and the open bite of the mental subnormality were slightly higher than that of the normal. The other handicapped groups showed no significant difference $(P\leq0.05)$ to the normal.

• The korean journal of orthodontics
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• v.14 no.1
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• pp.53-65
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• 1984

The purpose of this study was to investigate the histopathological change and adaptation process of the mandibular joint of the rat by muscle alteration. For this study, one hundred and twenty eight rats of 25 - and 60 - day old of age were used. Unilateral and bilateral detachment, with anterior positioning of the Masseter muscle, was performed under anesthesia. The animal was sacrified 10, 20, 50, 80 days postoperatively. This alteration in muscle function led to change in neuromuscular activity and demonstrated the adaptive nature of the condyle cartilage to functional demand. The results were as follows : 1. In the right muscle detached group, operated at 25 days of age, marked decrease on the chondroblastic zone was found in the condyle head on the right side of animals examined 10 days postoperatively. Comparing with the control group, no difference was found on the chondroblastic zone in the condylar head of animals examined 20, 50 and 80 days postoperatively. 2. In the bilateral muscle detached group, operated at 25 days of age, the chondroblastic zone was slightly decreased in the anterior parts of condylar head of animals examined 10 days postoperatively. 3. In the unilateral and bilateral muscle detached group, operated at 60 days of age, no significant change was found in the mandibular joint regardless of the post operative experimental periods. 4. Under Toluidine blue staining, slightly decreased metachromasia was found in the condyle head on the right side of unilateral experimental animals, operated at 25 days of age and examined 10 days postoperatively. 5. Under Masson's trichrome staining, increased metachromasia was found in the condyle head on the right side of unilateral experimental animals, operated at 25 days of age and examined 10 days postoperatively. In summary, the condyle of the rat could respond to changes in neuromuscular activity depend on the level of maturation of the tissue, because the endochondral bone formation of the condyle of the rat was almost ended within 3 months.

• The korean journal of orthodontics
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• v.23 no.3 s.42
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• pp.391-403
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• 1993

For the purpose of investigating mesiodistal axial inclination of posterior teeth in normal occlusion group, open bite and deep bite group and investigating the correlationship between the axial inclination of posterior teeth and overbite of anterior teeth, a cephalometric study was performed on the subjects consisted of normal occlusion group(40), open bite group(71 : Angle's Class I, Class II, division 1 25, Class III 25) and deep bite group(64 : Angle's Class I 23, Class II, division 1 21, Class III 20). Mesiodistal axial inclination of posterior teeth to occlusal, mandibular and palatal plane were measured. The findings of this study were as follows : 1. Upper and lower posterior teeth were more mesially inclined to occlusal plane in open bite group than in deep bite group. 2. Lower posterior teeth were more mesially inclined in deep bite group than in open bite group in Angle's Class II, division 1 malocclusion but there were no significant differences in Angle's Class I and Class III malocclusion. 3. There was no significant correlationship between the axial inclination of posterior teeth to each plane and overbite of anterior teeth in open bite group. 4. There was a significant correlationship between the axial inclination of upeer and lower second premolar to occlusal plane and overbite of anterior teeth in Angle's Class I, Class II, division 1 and Class III malocclusion.

• The korean journal of orthodontics
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• v.23 no.3 s.42
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• pp.375-389
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• 1993

The delivery of optimal orthodontic treatment is greatly influenced by a clinician's ability to predict and control tooth movement achieved by applying known force systems to the dentition. It is important to determine the location of the center of resistance of a tooth or group of teeth to better understand the nature of their displacement characteristics under the various force levels. The purpose of this study was to define the location of the centers of resistance of various units of the upper anterior segment for lingually directed 100gm and 200gm force in a dry human skull. The units investigated were composed of four incisors and six anterior teeth. In addition, the effect of change in force magnitude on the location of the center of resistance of these units was investigated. The laser reflection technique was used to measure the initial displacements of the consolidated teeth under loading. The results were as follows: 1. The instantaneous center of resistance for the four anterior teeth was located vertically between level 4 and level 5-that is, at $37.4\%$ apical to the cementoenamel junction level. 2. The instantaneous center of resistance for the six anterior teeth was located vertically just beneath level 5-that is, at $50.3\%$ apical to the cementoenamel junction level. 3. Increasing force levels had little effect on the location of the center of resistance of a given unit. 4. The location of the instantaneous center of resistance shifted apically as the number of dental units consolidated increased.

• The korean journal of orthodontics
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• v.23 no.3 s.42
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• pp.359-374
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• 1993

At present, many orthodontists regard the root parallelism of the posterior teeth important not only in diagnosis and treatment planning but also for predicting posttreatment stability. To evaluate it, they usually refer to the orthopantomogram. At this study, 97 samples were collected from students of Yonsei University, who have well-proportioned face, Angle's class I canine & molar relationships and no crown axis deviation of the posterior teeth including canines. Reliability of the root parallelism observed from orthopantomogram was evaluated by comparison with $45^{\circ}$ oblique cephalogram. The results were as follows : 1. In comparing the differences between anglular measurements in $45^{\circ}$ oblique cephalogram & orthopantomogram with $5^{\circ}$, those to mandibular plane were significantly less than to occlusal plane in number of items which showed less differences than $5^{\circ}$. 2. Compared the root parallelisms in the orthopantomogram with those in $45^{\circ}$ oblique cephalogram with $1\%$ significance level, parallelism between upper canine & 1st premolar, lower canine & 1st premolar, lower 1st premolar & 2nd premolar, and lower right 2nd molar & 3rd molar showed statistically significant differences. 3. When the significance between the differences of the root parallelism between above two kinds of film and $5^{\circ}$ was verified by two sided paired t-test, more or less large difference was shown between lower right 2nd molar & 3rd molar, a little larger than $5^{\circ}$ between lower canine & 1st premolar, smaller at the rest of them. 4. In $45^{\circ}$ oblique cephalogram, lower canine & 1st premolar showed convergent root arrangements each other, while in orthopantomogram they were divergent each other. All the others except them showed convergency on the upper, divergency on the lower in both films.

• The korean journal of orthodontics
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• v.24 no.4 s.47
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• pp.773-785
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• 1994

It has been generally believed that the impaction or eruption of mandibular third molars has significant correlations with the growth of the mandible, size of mandibular arch and size of teeth. The purpose of this study was to examine if there is any correlation between the status of eruption of mandibular third molars and the amount of mandibular crowding. The effect of missing of third moalrs to mandibular crowding was studied as well. 140 adult students of Yonsei University were selected and divided into three groups according to the status of mandibular third molars, Group 1) congenital missing group, Group 2) eruption group, and Group 3) impaction group. The tooth size, dimensions of the mandibular dental arch, and the amount of crowding were measured and compared. Results were as follows ; 1. There was no statistically significant difference in tooth size between the missing group and the eruption group(p<0.05). Impaction group showed larger total tooth material, inci- sal tooth material, and individual tooth size except central incisors compared to missing group (p<0.05). Impaction group showed larger total tooth material, incisal tooth material compared to eruption group as well(p<0.05). When individual tooth size was compared, impaction group had larger central incisors, canines, and second premolars than eruption group(p<0.05). 2. Missing group showed larger intermolar width than impaction group and it was stati- stically significant(p<0.05). 3. When compared the amount of total crowding, impaction group showed the largest am- ount of crowding, then eruption group, and missing group showed the least amount of crowding respectively(p<0.05). There was no statistically significant difference between missing stoup and eruption group in the amount of incisal crowding(p<0.05). Impaction group show- ed the largest amount of incisal crowding among all three groups(p<0.05).

• The korean journal of orthodontics
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• v.24 no.4 s.47
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• pp.897-916
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• 1994

The biologic potential, which is different from the piezoelectric signals, relates tooth movement at least in part to changes in bone metaboliosm in bioelectric theory. The purpose of this experiment was to determine wheather the application of half sine-wave pulsed electromagnetic fields (HSPEMF) could increase both the rate and amount of orthodontic tooth movement. Forty-three male Hartley guinea pigs, weighting approximately 255g, were utilized in this study. The animals were 35 days old at the start of the study. Laterally directed orthodontic force was applied to the maxillary central incisors of 40 Hartley guinea pigs (20 experimental, 20 control). According to the amount of orthodontic force (6g, 12g), they were divided into two sub-groups (10 experimental I, 10 experimental II, 10 control I, 10 control II). During the experimental period, experimental animals were placed in plastic animal holders with their heads positioned in an area of uniform electromagnetic field. Control animals were placed in similar plastic holders that did not carry the electric apparatus. The results were as follows : 1. The application of a HSPEMF to the experimental groups significantly increase the final amount of orthodontic tooth movement observed over a 10-day experimental period. 2. The application of a HSPEMF to the experimental groups significantly increase the velocity of orthodontic tooth movement observed over a 10-day experimental period. 3. There was no significant difference in the final amount of orthodontic tooth movement at the fourth day to the eighth day, but there was significant difference in the final amount of orthodontic tooth movement at the nineth, tenth day during a 10-day experimental period. 4. After 10 days of HSPEMF exposure & orthodontic force, the experimental groups demonstrated more osteodasts in the pressure side than control groups.

• The korean journal of orthodontics
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• v.32 no.2 s.91
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• pp.71-78
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• 2002

It could be suggested that adult orthodontic patients may have peculiar psychological features as well as different periodontal tissue conditions compared with adolescent patients. The aims of the present investigation were to explore the relationships between psychological characteristics and treatment compliance of patient to orthodontist and assistants (dental hygienists). Two types of locus of control data (I-score, Internal locus of control score ; E-score, External locus of control score) were obtained for 312 adult patients and 765 adolescents and then analyzed in relation to their sex and treatment compliance. In general, orthodontic patients showed higher I-score trends than ordinary persons and adult patients manifested higher I-score than adolescent patients. Unlike adult patients, female adolescent patients showed higher I-score than male adolescent patients. Adult patients with higher E-score and adolescent patients with higher I-score than their counter-part subgroup were classified into more compliant group. Orthodontist performed more generous decision about patients' compliance than assistants. The results of this study also suggest that psychological survey in orthodontic field could comprise useful diagnostic criteria.