• The korean journal of orthodontics
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• v.45 no.2
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• pp.59-65
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• 2015

Objective: To investigate skeletal and dental changes after application of a mandibular setback surgery-first orthodontic treatment approach in cases of skeletal Class III malocclusion. Methods: A retrospective study of 34 patients (23 men, 11 women; mean age, $26.2{\pm}6.6years$) with skeletal Class III deformities, who underwent surgery-first orthodontic treatment, was conducted. Skeletal landmarks in the maxilla and mandible at three time points, pre-treatment (T0), immediate-postoperative (T1), and post-treatment (T2), were analyzed using cone-beam computed tomography (CBCT)-generated half-cephalograms. Results: The significant T0 to T1 mandibular changes occurred $-9.24{\pm}3.97mm$ horizontally. From T1 to T2, the mandible tended to move forward $1.22{\pm}2.02mm$, while the condylar position (Cd to Po-perpendicular plane) shifted backward, and the coronoid process (Cp to FH plane) moved vertically. Between T1 and T2, the vertical dimension changed significantly (p < 0.05). Changes in the vertical dimension were significantly correlated to T1 to T2 changes in the Cd to Po-perpendicular plane (r = -0.671, p = 0.034), and in the Cp to FH plane (r = 0.733, p = 0.016), as well as to T0 to T1 changes in the Cp to Po-perpendicular plane (r = 0.758, p = 0.011). Conclusions: Greater alterations in the vertical dimension caused larger post-treatment (T2) stage skeletal changes. Studying the mandibular position in relation to the post-surgical vertical dimension emphasized the integral importance of vertical dimension control and proximal segment management to the success of surgery-first orthodontic treatment.

• The korean journal of orthodontics
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• v.46 no.5
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• pp.269-279
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• 2016

Objective: Rapid maxillary expansion (RME) is used to expand the maxilla and increase arch perimeter; yet, there are few reports on its effects on the sphenoid bone. With cone-beam computed topography (CBCT), it is possible to visualize sphenoid bone changes. The purpose of this study was to investigate sphenoid bone changes observed in conjunction with RME treatments, using CBCT. Methods: Sixty patients (34 women and 26 men, aged 11-17 years) underwent RME as part of their orthodontic treatment. Patients were randomly assigned to one of three groups: a tooth-anchored group, a bone-anchored group, or a control group. Initial CBCT scans were performed preceding the RME treatment ($T_1$) and again directly after the completion of expansion ($T_2$). Statistical analysis included ANOVA, descriptive statistics, and the intraclass correlation coefficient (ICC). Results: The reliability of the landmark location was at least 0.783, and the largest ICC mean measurement error was 2.32 mm. With regard to distances, the largest change was 0.78 mm, which was not statistically significant (p > 0.05). Statistical significance was established in patient groups of the same sex and treatment type for the following distance measurements: right anterior lateral pterygoid plate to the right edge of the hypophyseal fossa ($d_2$), anterior distance between the medial pterygoid plates ($d_4$), and anterior distance between the left medial and lateral plates ($d_8$). Conclusions: In this study, there were no clinically significant changes in the sphenoid bone due to RME treatments regardless of sex or treatment type.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.37
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• pp.33.1-33.9
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• 2015

Background: The porion (Po) is used to construct the Frankfort horizontal (FH) plane for cephalometrics, and the external auditory meatus (EAM) is to transfer and mount the dental model with facebow. The classical assumption is that EAM represents Po by the parallel positioning. However, we are sometimes questioning about the possible positional disparity between Po and EAM, when the occlusal cant or facial midline is different from our clinical understandings. The purpose of this study was to evaluate the positional parallelism of Po and EAM in facial asymmetries, and also to investigate their relationship with the maxillary occlusal cant. Methods: The 67 subjects were classified into three groups. Group I had normal subjects with facial symmetry ($1.05{\pm}0.52mm$ of average chin deviation) with minimal occlusal cant (<1.5 mm). Asymmetry group II-A had no maxillary occlusal cant (average $0.60{\pm}0.36$), while asymmetry group II-B had occlusal cant (average $3.72{\pm}1.47$). The distances of bilateral Po, EAM, and mesiobuccal cusp tips of the maxillary first molars (Mx) from the horizontal orbital plane (Orb) and the coronal plane were measured on the three-dimensional computed tomographic images. Their right and left side distance discrepancies were calculated and statistically compared. Results: EAM was located 10.3 mm below and 2.3 mm anterior to Po in group I. The vertical distances from Po to EAM of both sides were significantly different in group II-B (p=0.001), while other groups were not. Interside discrepancy of the vertical distances from EAM to Mx in group II-B also showed the significant differences, as compared with those from Po to Mx and from Orb to Mx. Conclusions: The subjects with facial asymmetry and prominent maxillary occlusal cant tend to have the symmetric position of Po but asymmetric EAM. Some caution or other measures will be helpful for them to be used during the clinical procedures.

• The korean journal of orthodontics
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• v.29 no.3 s.74
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• pp.317-325
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• 1999

In proper diagnosis of skeletal Class III malocclusion, it was important to know the pattern of three dimensional skeletal & facial disharmony. The purpose of this study was to obtain P-A cephalometric characteristics in skeletal Class III malocclusion comparing with normal occlusion. The samples were consisted of 120 subjects, divided into four groups : Male normal occlusion, Female normal occlusion, Male skeletal Class III malocclusion, Female skeletal Class III malocclusion. Posteroanterior and lateral cephalogram were taken from the subjects with a x-ray apparatus (ASHAI CX90SP, Japan) and traced on acetate paper with routine manner. The transverse and vertical values from posteroanterior cephalometry, the sagittal values from lateral cephalometry and their ratio were obtained. The results were as follows: 1. The anteroposterior discrepancy in skeletal Class III group was not due to short maxillary length(Cd-A), but to longer mandibular length(Cd-Gn) than normal occlusion group. 2. The faces of skeletal Class III group were longer than normal occlusion group. It was not due to increase of upper face height(Cg-ANS) but to increase of the lower face height(ANS-Me) especially mandibular height(Cd-Me). 3. There was no difference in the facial width values between normal occlusion group and skeletal Class III group, except upper molar width(U6-U6), lower molar width(L6-L6) and mandibular width(Ag-Ag) of female skeletal Class III group which were larger than normal occlusion group. 4. The increase of mandibular length of skeletal Class III group was reflected in the increase of lower facial height but did not have an effect on the mandibular width.