• Maxillofacial Plastic and Reconstructive Surgery
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• v.34 no.2
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• pp.106-111
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• 2012

Purpose: The aim of this sturdy was to assess the prevalence and change in pathologic findings in the maxillary sinus by using preoperative and postoperative cone-beam computed tomography (CBCT). Methods: The subjects included 83 patients with maxillary sinus abnormalities who underwent orthognathic surgery between January 2010 to December 2010. The CBCT analyses were classified according to the thickness of maxillary sinus membrane; Normal (membrane thickness<2 mm), mucosal thickening (membrane thickness ${\geq}2mm$ and <6 mm), partial opacification (membrane thickness>6 mm but not complete), total opacification, and polypoidal mucosal thickening. The diameters of the maxillary sinus ostium on the coronal cross-sectional view were also calculated. Results: Out of 166 maxillary sinuses in 83 patients, 42 (25.3%) maxillary sinuses before surgery and 37 (22.3%) maxillary sinuses after surgery showed abnormalities. A decrease in the diameters of maxillary ostium was observed after surgery (P<0.05). However, there was no significant difference in mucosal thickness both, preoperatively and postoperatively. Conclusion: The orthognathic surgery didn't deteriorate the maxillary sinus abnormaility. Despite the low prevalence of sinus complications in orthognathic surgery, all the patients should be informed of the possibility of sinusitis that could require the surgical intervention before surgery.

• The korean journal of orthodontics
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• v.15 no.2
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• pp.211-227
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• 1985

The purpose of this study was to analyze the stress distribution and the displacement in the maxillary complex after the application of the three kinds of the head gear. (high pull head gear, straight pull head gear, cervical pull head gear.) Orthopedic force, 300 gram, was applied to the maxilla of the dry human skull in a high, straight and cervical direction. The stress distribution and the displacement within the maxillary complex was analyzed by a 3-dimensional finite element method. The results were as follow: 1. In won, the stress of conical pull head gear was the greatest stress and straight pull head gear was the medium stress and high pull head gear was the least stress. 2. The compressive stress was observed on the anterior portion of premaxilla, especially anterior nasal spine area, when the three kinds of head gear were applied to the dry kuman skull. 3. It appeared that the stress of the anterior portion of the zygomatic bone was greater than the posterior portion in the case of three kinds of head gear application and compressive stress was noted only at the below of the frontozygomatic suture of the zygomatic bone. 4. The backward, upward, sideward displacement of the alveolar area was observed in a high pull head gear application but in the case of straight pull head gear and cervical pull head gear application, the backward, downward, sideward displacement was observed. 5. The forward, downward, sideward displacement was observed on the midpalatine suture and premaxilla on the sagittal plane and transverse palatine suture in the case of three kinds of headgear application.

• The korean journal of orthodontics
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• v.12 no.1
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• pp.15-20
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• 1982

The requirement of ideal orthodontic direct bonding adhesive should include longevity of bond, ability to withstand a variety of forces, resistance to the degrading effects of the oral environment, and ability to be easily removed without affecting the integrity of the enamel. The purpose of this study was to evaluate the adhesive properties of recently developed 3 orthodontic directbonding adhesives by testing the tensile strength. 75 premolars extracted for orthodontic treatment were used. The tensile strength was tested by Tensilon/UTM-1-10000C after 24 hours from bonding. Following results were obtained; The mean tensile strength of each product was higher than the maximum force $(29kg/cm^2)$ exerted on a bracket during orthodontic treatment. The tensile strength of Mono-Lok was statistically higher than Concise and Dyna-Bond, although there was no difference between the tensile strength of Concise and Dyna-Bond statistically. Of the filure, the combination type of failure $(68\%)$, where part of the adhesive remained on the tooth and part on the bracket was the most common type. The second type of failure $(22.7\%)$ occurred at the toothadhesive interface and the last type of failure $(9.3\%)$ occurred at the adhesive-bracket interface.

• The korean journal of orthodontics
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• v.20 no.3 s.32
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• pp.427-446
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• 1990

The objective of this study was to understand the major changes of craniofacial dimensions and spatial growth pattern during the late embryonic and fetal period of human fetures. This study was performed with the selective materials of normal fetuses received from the Registry of Congenital Malformation of Seoul National University Hospital. The specimens consisted of nineteen embryos and sixty-six fetuses. The photomicrographs from mid-segittal sections of embryos were used for angular measurement, and the lateral cephalograms taken with soft X-ray were also measured in liners and angular aspects. All of the anatomical landmarks for the tracing of the photomicrographs and cephalograms were referred to the previous reports on literature. The sequential changes of prenatal craniofacial dimensions and agles were analysed statistically and discussed on the focus about the developmental growth directions of human ore-facial structure arised from heterogeneous origins. The results are as follows, 1) Cranial base angle was almost formed at about 6 weeks old embryos with the average angle of $127.4{\pm}6.33^{\circ}$ (n=3) and it was almost constant onwards. 2) The linear increase rates of anterior cranial base length and anterior facial height exceeded those of the posterior cranial base length and posterior facial height, and the maxilla grows more rapidly on the horizontal dimension than the vertical dmension during the fetal period. 3) The angular relationship between the anterior cranial base and palatal plane decreasedslightly during the fetal period, disclosing $11^{\circ}$ at 12th week gestation and $5^{\circ}$ at 41th weeks gestation. 4) Genial angle was maintained almost constantly at about $130^{\circ}$ during the fetal period from 12 weeks to 41 weeks of gestation.

• The korean journal of orthodontics
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• v.36 no.6
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• pp.465-473
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• 2006

Objective: This study evaluated the effects of nitric oxide (NO) on the proliferation and differentiation of human periodontal ligament cells involved in orthodontic tooth movement. Methods: A range of concentrations of sodium nitroprusside (SNP), a NO donor, were administered to samples of human periodontal ligament cells, followed by measurement of cell viability, alkaline phosphatase (ALP) activity, and expression of osteonectin and bone sialoprotein. Results: Cell viability, ALP activity and the expression of osteonectin and bone sialoprotein were increased in human periodontal ligament cells treated with SNP concentrations of < 0.2 mM compared with controls, but were decreased with SNP concentrations of > 1.0 mM. Conclusion: NO has a biphasic effect on proliferation and differentiation in human periodontal ligament cells, with a stimulatory effect at low concentrations and an inhibitory effect at high concentrations.

• The korean journal of orthodontics
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• v.27 no.4 s.63
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• pp.633-641
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• 1997

Spatial change of craniofacial structures from growth or orthopedic force is usually evaluated by cephalometric superimpositions at different points in time.As the evaluation cu be changed according to cephalometric superimposition method,selettion for correct superimposition method is very important.Double registration of nineteen pairs of female lateral head films,their growth period is average 3.7 years and age is overage 10.7 years,were performed by two observers.Comparisions was made between two methods and the results revealed the following, 1. NS line and ACB superimpositions ate not markedly different in reliability due to almost same registration error of them. 2. The investigation was undertaken to examine interobserver difference.In NS line method, there is no significance in all measurements. In ACB method,significant difference was revealed in 4 measurements of 7 measurements was 3. In the investigation of intermethod difference, there is no significance between NS line and ACB superimpositions

• The korean journal of orthodontics
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• v.24 no.2
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• pp.433-445
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• 1994

Bonding of brackets is one of the essential factors for successful orthodontic treatment' so bond strength of orthodontic adhesives are very important. The purposes of this research were to compare shear bond strength of various orthodontic adhesives and to evaluate failure sites. One-hundred twenty extracted human first premolars were prepared for bonding and premolar brackets were bonded to prepared enamel surfaces with Super C Ortho, Mono-$Lok^2$, Transbond, and Super C Ortho after applying Fluorobond. After bonding of brackets, teeth specimens were divided into 3 groups. In group 1 specimens were stored at humidor $37^{\circ}C$ in 1 hour, in group 2 specimens were stored at humidor $37^{\circ}C$ in 24 hours, thermocycled 10 times and in group 3 specimens were stored at humidor $37^{\circ}C$ in 24 hours, thermocycled 1800 times. Then the universal testing machine Instron 6022, Instron Co., U.S.A. was used to test the shear bond strength of brackets to enamel. After debonding, brackets and enamel surfaces were examined under stereoscopic microscope to determine the failure sites The results were as follows : 1. Shear bond strength was significantly highest of using Super C Ortho after applying Fluorobond and Super C Ortho In group 1, was highest of using Super C Ortho in group 2, and was highest of using Mono-$Lok^2$ in group 3. 2. According to time and temperature change, in using Super C Ortho the group 2 had significantly highest strength and group 3 had lowest strength, in using Mono-$Lok^2$ the group 2 and had higher strength than group 1 and in using Super C Ortho after applying Fluorobond shear bond strength decreased constantly, 3. The failure sites were tooth-resin interface in Super C Ortho after applying Fluorobond, Mono $Lok^2$ and Transbond and were at almost same ratio bracket base-resin interface and tooth-resin interface in Super C Orth.

• The korean journal of orthodontics
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• v.24 no.2
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• pp.349-366
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• 1994

The method of treatment in skeletal Class III malocclusion must be chosen according to an etiology and timing of the treatment. Maxillry protraction has been used as an effective treatment method in growing children with maxillary deficiency. The efficacy of maxillary protraction has been viewed as a result of downward-backward displacement of mandible and compensatory dental displacement during the treatment rather than forward -downward growth of maxilla itself. In this study, 104 subjects treated with maxllary protraction, and 19 males and 21 females with known annual growth amount have been chosen longitudinally as treated group and normal group, respectively. And changes in position of maxilla, mandible and dentition have been comparatively analyzed on the lateral cephalometric radiographs by age. The results were as follows : 1. Treated group showed more forward movement of maxilla compare to the normal group and the mandible displaced backward compare to the normal group. 2. Downward movement of maxilla in treated group was similar to that of normal group with statistical signigicance in female 12 year old group and downward movement of mandible in treated group was similar to that of normal group. 3. In treated group, maxillary central incisor moved more forward than the normal group with statistical significance in male 8, 10 year-old groups and female 8, 9, 10 year-old groups. In treated group, downward movement of maxillary central incisor was similar to that of the normal group with statistical significance in male and female 7,8 year-old groups. Considering the above results and the duration of the treatment, the forward movement of maxilla due to maxillary protraction was effective compared to normal growth amount of the normal group.

• The korean journal of orthodontics
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• v.45 no.3
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• pp.113-120
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• 2015

Objective: This study compared occlusal contact areas of ideally planned set-up and accomplished final models against the initial in class I and II molar relationships at finishing. Methods: Evaluations were performed for 41 post-orthodontic treatment cases, of which 22 were clinically diagnosed as class I and the remainder were diagnosed as full cusp class II. Class I cases had four first premolars extracted, while class II cases had maxillary first premolars extracted. Occlusal contact areas were measured using a three-dimensional scanner and RapidForm 2004. Independent t-tests were used to validate comparison values between class I and II finishings. Repeated measures analysis of variance was used to compare initial, set up, and final models. Results: Molars from cases in the class I finishing for the set-up model showed significantly greater contact areas than those from class II finishing (p < 0.05). The final model class I finishing showed significantly larger contact areas for the second molars (p < 0.05). The first molars of the class I finishing for the final model showed a tendency to have larger contact areas than those of class II finishing, although the difference was not statistically significant (p = 0.078). Conclusions: In set-up models, posterior occlusal contact was better in class I than in class II finishing. In final models, class I finishing tended to have larger occlusal contact areas than class II finishing.

• The korean journal of orthodontics
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• v.46 no.3
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• pp.171-179
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• 2016

Objective: The primary aim of the study was to generate new prediction equations for the estimation of maxillary and mandibular canine and premolar widths based on mandibular incisors and first permanent molar widths. Methods: A total of 2,340 calculations (768 based on the sum of mandibular incisor and first permanent molar widths, and 1,572 based on the maxillary and mandibular canine and premolar widths) were performed, and a digital stereomicroscope was used to derive the the digital models and measurements. Mesiodistal widths of maxillary and mandibular teeth were measured via scanned digital models. Results: There was a strong positive correlation between the estimation of maxillary (r = 0.85994, $r^2=0.7395$) and mandibular (r = 0.8708, $r^2=0.7582$) canine and premolar widths. The intraclass correlation coefficients were statistically significant, and the coefficients were in the strong correlation range, with an average of 0.9. Linear regression analysis was used to establish prediction equations. Prediction equations were developed to estimate maxillary arches based on $Y=15.746+0.602{\times}sum$ of mandibular incisors and mandibular first permanent molar widths (sum of mandibular incisors [SMI] + molars), $Y=18.224+0.540{\times}(SMI+molars)$, and $Y=16.186+0.586{\times}(SMI+molars)$ for both genders, and to estimate mandibular arches the parameters used were $Y=16.391+0.564{\times}(SMI+molars)$, $Y=14.444+0.609{\times}(SMI+molars)$, and $Y=19.915+0.481{\times}(SMI+molars)$. Conclusions: These formulas will be helpful for orthodontic diagnosis and clinical treatment planning during the mixed dentition stage.