• The korean journal of orthodontics
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• v.35 no.3 s.110
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• pp.182-195
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• 2005

The purpose of this retrospective study was to estimate the pretreatment characteristics of growing patients with Class II malocclusion. who had been treated with maxillary second molar extractions The sample comprised of 51 subjects; 18 subjects were classified into the molar extraction group, and 33 subjects were treated without extraction and classified into the nonextraction group. Pretreatment lateral cephalograms were calculated and analyzed by independent t-test and stepwise discriminant analysis. In measurements for skeletal pattern, no anteroposterior measurements and proportions of various vertical dimensions were significantly different. and only some measurements such as $AB-MP(^{\circ)$, Na-We(mm), AVD (mm) were significantly different between the two treatment groups (p<0.05). In measurements for dentoalveolar pattern. some measurements, which were related to the position and angulation of the upper and lower permanent first molars, and the angulation of the upper third molars, were significantly different between the two treatment groups In particular, the maxillary second molar extraction group exhibited more mesial angulation of maxillary first molar to the occlusal plane.

• The korean journal of orthodontics
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• v.41 no.2
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• pp.76-86
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• 2011

Objective: To investigate whether the accuracy of 3D laser scanning is influenced by the angles and number of scans. Methods: Using a 3D laser scanner, 10 manikins with facial markers were scanned at 7 horizontal angles (front view and at $20^{\circ}$, $45^{\circ}$, and $60^{\circ}$ angles on the right and left sides). Three-dimensional facial images were reconstructed by 6 methods differing in the number and angles of scans, and measurements of these images were compared to the physical measurements from the manikins. Results: The laser scan images were magnified by 0.14 - 0.26%. For images reconstructed by merging 2 scans, excluding the front view; and by merging 3 scans, including the front view and scans obtained at $20^{\circ}$ on both sides; several measurements were significantly different than the physical measurements. However, for images reconstructed by merging 3 scans, including the front view; and 5 scans, including the front view and scans obtained at $20^{\circ}$ and $60^{\circ}$ on both sides; only 1 measurement was significantly different. Conclusions: These results suggest that the number and angle of scans influence the accuracy of 3D laser scanning. A minimum of 3 scans, including the front view and scans obtained at more than $45^{\circ}$ on both sides, should be integrated to obtain accurate 3D facial images.

• The korean journal of orthodontics
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• v.27 no.1
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• pp.65-78
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• 1997

This study was carried out in order to determine soft tissue response to incisor movement and mandibular repositioning and to determine feasibility of predicting vertical and horizontal changes in soft tissue with hard tissue movement. For this study, cephalometric records of 41 orthodontically treated adult females who had Angle's Class II division 1 malocclusion were selected and stepwise multiple regression analysis was employed. Following conclusions were obtained by analysing the changes of soft tissue and hard tissue before and after treatment. 1. Hard tissue measurements that showed significant changes before and after treatment were horizontal and angular changes of maxillary incisor, horizontal,vertical and angular changes of mandibular incisor, overjet, overbite, interincisal angle, mandibular repositioning, A,B, skeletal convexity and soft tissue measurements that showed significant changes were horizontal, thickness and angular changes of upper lip, horizontal and angular changes of lower lip, interlabial angle, nasolabial angle labiomental angle, Sri, Ss, Si and soft tissue convexity(P<0.05). 2. All Soft tissue measurements changed significantly before and after treatment had between one and four hard tissue independent variables at statistically significant level, indicating that all soft tissue changes were direct relationship with hard tissue changes 3. Ova jet, horizontal change of maxillary incisor, horizontal change of maxillary root apex and horizontal change of pogonion entered into prediction equations most frequentely indicating that they were more significant variables in prediction of vertical and horizontal changes in the soft tissue with treatment, but vertical changes of mandibular incisor not entered any prediction equations, indicating that it was not considered a good predictor for soft tissue changes with maxillary incisor retraction. 4. Horizontal and vertical changes in subnasale were found to have most independent variables, significant at the 0.05 level in prediction-equations(${\Delta}$Sn(H):Ur, Is(H), Pg(H), UIA,${\Delta}$Sn(V): Is(H), Pg(H), overjet, A), indicating that subnasale changes are influenced by complex hard tissue interaction. 5. Multiple correlation coefficient($R^2$) of the soft tissue prediction equations ranges from 0.2-0.6.

• The korean journal of orthodontics
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• v.30 no.5 s.82
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• pp.553-563
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• 2000

Horseshoe Expander is one of Slow Maxillary Expansion(SME) which aims to accommodate the contra- lateral expansion and midpalatal suture expansion or the palate. The appliance consists of skeleton type strew embedded in split Horseshoe appliance. It is the objectives of the presentation to manifest the changes in dental & craniofacial components subsequent to the application of Horseshoe Expander. The subjects for this study consisted of 32 patients (mean age : 12.7). frontal, lateral cephalometric headfilm were taken and study casts were fabricated before and after expansion. 24 items were measured, compared preexpansion with postexpansion. Especially, palatal volume was measured by means of 'Hydro-measurement method'. Tooth axis measurement on the dental casts were made with Universal bevel protractor, and Horseshoe Expander group were compared with RME group. This study of changes to maxillary expansion with Horseshoe Expander revealed the following significant results. 1. Triangular-shaped expansion pattern appeared in frontal cephalometric headfilm. 2. Palatal plane, occlusal plane, mandibular plane and upper incisor to FH increased in lateral cephalometrir headfilm. 3. Palatal volume increased significantly. A slight bite opening, reduction of occlusal contact points showed in dental casts. 4. A 2.2:1 ratio of the amount of intermolar width in maxilla(orthodontic movement) to maxillary width (orthopedic movement) was determined. 5. Horseshoe Expander group has less buccal tipping tendency than RME group, by taking high correlation coefficients in the upper second premolar and first molar. It was suggested that Horseshoe Expander showed less orthodontic changes, less buccal tipping tendency. In addition, it was effective in maxillary expansion.

• The korean journal of orthodontics
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• v.37 no.6
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• pp.421-431
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• 2007

The objective of this study was to provide guidelines for the diagnosis and successful treatment of orthodontic treatment with upper premolar extraction only Methods: The sample group consisted of 40 patients (20 with upper premolar extraction only, 20 with both upper and lower premolar extractions) who showed an overjet of more than 7 mm and were finished successfully. Lateral cephalographs were taken before and after orthodontic treatment. Landmarks showing the position of the upper and lower incisors and the position of the upper and lower lip were determined and angular measurement of these values were obtained for statistical analysis (Mann-Whitney test). Results: At pre-treatment, the position of the lower incisor was less labially inclined and the convexity of the lower lip was smaller in the upper premolar extraction only group than in the upper/lower premolar extraction group. At post-treatment, there was no difference in all measurements except for the position of the lower incisor. A comparison of changes between pre- and post-treatment showed that the retraction of upper & lower incisors and the decrease in convexity of the lower lip were greater in the upper/lower premolar extraction group. Conclusions: Treatment by upper premolar extraction can be of benefit for patients whose lower incisor proclination and lower lip protrusion are not excessive.

• The korean journal of orthodontics
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• v.28 no.4 s.69
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• pp.547-561
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• 1998

Obstructive sleep apnea (OSA) is a disorder characterized by repetitive episode of upper airway collapse during sleep. Recent studies showed that not only the anatomic factors but the physiologic factors of the upper airway also have effcts on the occurrence of apnea and that the genioglossus muscle also plays an important role in the maintenance of the upper airway. A variety of therapies were performed to treat OSA, and among them the use of mandibular repositioning appliances showed reasonable results. But there is still a lack of research on the structural and physiological mechanism upon the use of mandibular repositioning appliances. The author selected 26(male 17, female 9) OSA patients that came to the Yonsei University Dental Hospital, Department of Orthodontics, and 20 normal adults (male 10, female 10) and took cephalometric radiographs of them in a supine position before and after the placement of the mandibular repositioning appliance to see the structural changes of the upper airway and compare the therapeutic effects between the two groups. We also studied the waking genioglossus muscle activity in OSA patients and investigated the difference in the electromyogram of the genioglosssus muscle upon the change in body posture and the use of mandibular repositioning appliance. Following results were obtained. 1. Among the cephalometric measurements of the upper airway structure, the length of the soft palate, maximum thickness of the soft Palate and SPAS, MAS, VAL, H-H1, MP-H showed statistically significant differences between the normal and OSA groups, but the IAS and EAS showed no statistically significant differences between the two groups. 2. In both the normal and OSA groups, as the epiglottis moved forward on wearing the mandibular repositioning appliance, the epiglottis level of the upper airway increased and the maximum thickness of the soft palate changed and the hyoid bone also moved forward, but the IAS in both groups showed various results and the effect of the mandibular repositioning appliance on the structure of the upper airway was different in the two groups. 3. Upon changing the position, the electromyogram of the genioglossus muscle showed a increasing tendency but there was no statistically significant differences, and when the mandibular repositioning appliance were worn there was a statistically significant increase in the electromyogram of the genioglossus muscle in both the upright and supine positions. The mandibular repositioning appliances not only have an effect on the anatomical structure of the upper airway but also on the physiology of the upper airway. There are different responses to the use of mandibular repositioning appliance between the normal and OSA groups therefore it could be considered to have the different physiology of the upper airway between the two groups.

• The korean journal of orthodontics
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• v.28 no.1 s.66
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• pp.17-27
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• 1998

Study on growth change of dental arch is considered to both an important data in orthodontic diagonsis and treatment planning as well as analysis of treatment results , also, arch form is important in anthropology and dentistry, even more so in prosthodontics and orthodontics. In the field of orthodontics, studies on the functional aspect of upper and lower teeth and maintenance of stability of dentition and occlusion were carried out from the early days. Some of the early studies include explanation of growth change in dental arch from measuring directly fom human stroll, and afterwards, cephalometrics x-rays were introduced; accordingly, studies using cephalometric measurement and linear measurements of study models were often performed. By this method, arch width, arch depth and perimeters were measured, and growth change or dental arch was studied. The subject ror this study were sn children(boys and girls or ages from 3 yens to 12 years from Kang-won district and Seoul, who has no history of orthodontic treatment and who show healthy status and normal growth and development. Cephalometric x-ray, panoramic x-ray, and study model were taken for each subject consecutively for 2 years, and the subjects are still followed up. 400 pairs of study models from the past two years were used in this study; mesio-distal diameater of each tooth, intercanine width, intermolar width, canine depth, molar depth and arch perimeters were measured. Afterwards, mean value and each standard deviation of each age group and each gender were obtained, and representation graph were drawn. The following conclusion were obtained. 1. Intercanine width showed gradual increase until the age of 10-years and after that, showed no increase. 2. Intermolar width in upper arch showed gradual increase : intermolar width in lower arch showed no significant chang, and after the age of 9-years, showed increase. 3. Cainine arch depth showed relatively rapid increase after the age of 6-years, and this pattern was more obvious in lower arch. 4. Molar arch depth increased gradually in both archs and it decrease after the age of 10-years : this phenomenon was more prominent in the lower arch. 5. Arch perimeter showed gradual inerease and convert to plateau at the age of 10-years, after that, it decreased. this pattern was more prominent in lower arch.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.147-152
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• 2013

Purpose: The aim of this study was to propose the position of maxillary anterior teeth and intercanine width measurements based on the incisive papilla in accordance with the cephalic type and gender of dentate Korean adult with normal teeth alignment. Materials and methods: 42 students with Class I normal occlusion, without crowding or spacing, were selected from the Chonnam National University School of Dentistry. The lateral skull radiographs of the subjects were taken and were classified as different cephalic types, based on their PFH / AFH ratios. 42 casts of their maxilla were prepared and both the distance between the upper central incisors and the middle of the incisor papilla was measured with a vernier caliper (A) and the distance between the maxillary canine cusp tips (B) were measured. Statistical analysis was performed using SPSS version 15 and their significance was investigated. Results: For dolichocephalic group, the mean values for A and B were 8.43 (SD: 0.61) and 36.73 (SD: 2.17), respectively. The mean value for A was 8.51 (SD: 1.27) for the mesocephalic group and 8.76 (SD 1.03) for the brachycephalic group. The mean value for B was 35.91 (SD: 1.86) for the mesocephalic group and 37.34 (SD: 2.23) for the brachycephalic group. For the male group, the mean A value was 8.86 (SD: 1.04) and the mean B value was 37.60 (SD: 0.24). For the female group, the mean A value was 8.41 (SD: 0.93) and the mean B value was 36.18 (SD: 2.01). The difference between male and female group in A values were not statistically significant (P>.05). The B values of the male subjects were greater than those of the female subjects and was statistically significant (P<.05). Conclusion: 42 students with normal dentition and occlusion in korea, the distance from the incisive papilla and the incisal edge of maxillary central incisors had no difference in cephalic type or gender. However, the distance between the cusp tip of both canines had significant difference in gender where the male showed higher values than the female, while having no difference in cephalic types.

• The korean journal of orthodontics
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• v.38 no.2
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• pp.104-120
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• 2008

Purpose: The purpose of this study was to assess the hard and soft tissue changes associated with mandibular bilateral sagittal split osteotomy and genioplasty. Methods: This is a retrospective study of 40 patients who underwent either bilateral sagittal split osteotomy for mandibular setback (BSSO group, n = 20) or in combination with advancement genioplasty (Genio group, n = 20). Lateral radiographs, were taken before and immediately after surgery, and at least 6 months after surgery. Results: Comparing hard and soft tissue changes between the BSSO group and Genio group, there were significant differences in the lower incisor, soft tissue B point (B'), and soft tissue Pogonion (Pg') (p < 0.5). The mean ratio of hard and soft tissue changes for B/B', Pg/Pg', and Menton/soft tissue Menton after surgery in the BSSO group was 0.997, 0.965, and 1.022 respectively, and 0.824, 0.602, and 0.887 respectively in the genio group. Significant differences were found between the two groups. There were significant differences in lip thickness (B-B', Pg-Pg') in the Genioplasty group between pre and postsurgery, but not in the BSSO group. Pogonion to Labrale inferior and B' had a correlation coefficient of 0.833, 0.922, respectively for the BSSO group, and 0.775, 0.799 for the Genio group. Conclusions: The results indicate that there is a significant difference between bilateral sagittal split osteotomy with or without genioplasty in the lower facial esthetics values. The combination of mandibular setback and genioplasty had a smaller change in soft tissue thickness of the symphysis area after surgery than that of mandibular setback only.

• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.251-265
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• 1999

Various types of horizontal reference planes are used for diagnosis, treatment planning and evaluation of treatment results. But these reference Planes lack accuracy and repro-ducibility, and are mainly for Caucasian. Unlike the adult patients who have completed growth, the horizontal reference planes for growing children may change continuously during growth. Therefore this must be considered in selecting the horizontal reference plane. The purpose of this study was to Investigate the angle formed by the Sella-Nasion(SN) plane and Frankfort-Horizontal(FH) plane and evaluate the angle formed by FH plane and other horizontal reference planes in relation to different skeletal maturity and malocclusion types. 540 subjects with no orthodontic treatment history were chosen, and hand -wrist X-rays and lateral cephalometric X-rays were taken. According to SMA(Skeletal Maturity Assessment) of hand-wrist X-rays, the subjects were classified into 3 skeletal maturity groups : SMI 1-4 for group A, SMI 5-7 for group B and SMI 8-11 for group C. A second classification was made according to cephalometric analysis of lateral cephalograms. The subjects were classified into 3 malocclusion groups : Skeletal Class I, II and III malocclusion group. 10 measurements were evaluated. The results were as follows. 1. The angle formed by the SN plane and FH plane showed no difference among skeletal maturity groups, malocclusion groups, and between .sexes. 2. The angles formed by the SN plane and FH plane were $8.27^{\circ}{\pm}2.31^{\circ}$ for males and $8.59^{\circ}{\pm}2.24^{\circ}$ for females. The average value for females and males was $8.42^{\circ}{\pm}2.28^{\circ}$. 3. The angle formed by the FH plane and palatal plane was almost constant showing no difference among skeletal maturity groups, malocclusion groups, and between sexes($1.09^{\circ}{\pm}3.21^{\circ}$).