• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.3
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• pp.214-220
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• 2001

The clinical application of the three-dimensional radiographic technique had been limited to standard Broadbent-Bolton cephalometer with biplanar stereoradiography. We developed a new method for compensating the error of head position in ordinary non-biplanar cephalostat. It became to possible to use the three dimensional cephalogram commonly in clinical bases. 1. The method of methemetical compensation of head positioning error in non-biplanar condition was evaluated with dry skull. The error of the method of first and the second trial was $0.46{\pm}1.21$, $0.33{\pm}0.90mm$, which means the error of the head positioning correction in conventional cephalogram was within clinical acceptance. 2. The reproducibility of this system for clinical application was 0.54 mm ($-2.99{\sim}2.26mm$) which defines the absolute mean difference of the first and second trial. Compare to the The landmark identification error $1.2{\pm}1.6mm$, the error of the measurement was within the range of landmark identification error. The result indicates the adequate clinical accuracy of the computation of three-dimensional coordinates by compensation of the error of the head position in ordinary non-biplanar cephalostat.

• Journal of Korean society of Dental Hygiene
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• v.10 no.4
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• pp.655-661
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• 2010

Objectives : This study is aimed to prevent the damage to the inferior alveolar nerve during the orthognathic surgery. Methods : The control group consist of 50 patients with class I occlusion. The experimental group consist of 50 patients with class III malocclusion. The cepalometric radiography was used to evaluate the position of the mental foramina. Results : In the first, mental foramen position of class III was more inferior 0.85 mm in the distance between base of mandible and mental foramen. But the distance between occlusal plan and mental foramen had not statistically significant. Secondly, mental foramen location of Mandibular Prognathism was more anterior 0.91 mm in the distance between coronal plane of mandible included pogonion point and mental foramen. Also, the distance of occlusal-coronal plane of mandible included central incisor and mental foramen had statistically significant. The mental foramen location of class III was more anterior 4.81 mm than class I patients. Conclusions : The result of this study could help the clinicians to apprehend fundamental data with various facial skeletal types for any related researches about the location of the mental foramina for other purposes.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.1
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• pp.185-194
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• 2001

This study was designed to evaluate the effects of angulation changes of head posture on the enlargement ratios of a lateral headfilm depending on the vortical or horizontal rotation of the objects. A device was constructed to measure regional changes of enlargement ratios. The device was held within the cephalostat and cephalograms recorded at each measured degrees of the device tilting, vertically and horizontally. The enlargement ratios of the horizontal, vertical, and angular measurements on the films taken at each tilted angulations were obtained and compared with those on the films taken without rotation. In summary, the enlargement ratios of the horizontal linear measurements were decreased during horizontal rotations. The enlargement ratios of vortical measurements of the right side on the film were increased and those of the left side were decreased by the horizontal rotations. Enlargement ratios of horizontal measurements were affected further than those of vertical measurements by the same angular changes of the horizontal rotations. Therefore, a disruption of parallelism between the object's midsagittal plane and the film could result in distortion of the image while vertical rotation around the object's porionic axis would not significantly affect the enlargement ratios on the headfilm.

• 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.

• The korean journal of orthodontics
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• v.35 no.4 s.111
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• pp.251-261
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• 2005

Enlargement is an inherent property of X-rays which occurs when straight hues diverse from small a focal spot. The purpose of the present study was to evaluate the validity of the correction of gonial angle width enlarged on frontal cephalogram, using frontal and lateral cephalograms taken orthogonally from each other. In 40 adult individuals, frontal and lateral cephalograms were taken at a $90^{\circ}$ angle using the Head Posture Aligner. The angle width was measured on the frontal cephalogram and subsequently. the corrected angle width was calculated using the magnification rate of two cephalograms. Measured and corrected angle widths were compared with the measurement from the 3D CT image. The measurement or the frontal cephalogram showed a 9.10mm of enlargement on average ranging from 7.92 to 11.31mm. Corrected angle width measurement showed a 0.14mm difference with the 3D CT image measurement, which was not statistically significant. The results of the study indicate that actual au91e width can be approached through calculation using frontal and lateral cephalograms taken orthogonally with the help of the Head Posture Aligner The study also showed that the magnitude of correction error did not show a significant correlation with the amount of menton deviation, and it suggests that the present correction method is valid even in individuals with severe facial asymmetry.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.21 no.2
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• pp.174-188
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• 1999

The purpose of this study is to evaluate the precision and accuracy of a three dimensional cephalogram constructed by using the frontal and lateral cephalogram of twelve human dry skulls. After achieving the three dimensional image reconstruction program, we tried to apply this program to two dentofacial deformity patients. 1. Conventional nasion relator in cephalostat was used to reproduce the same head position for the same dry skull. The mean difference of the three dimensional cephalogram for the same dry skull was $0.34{\pm}0.33mm$. Closeness of repeated measures to each skull reveals the precision of this method for the three dimensional cephalogram. 2. Concerning the accuracy, the mean difference between the three dimensional reconstruction data and actual lineal measurements was $1.47{\pm}1.45mm$ and the mean magnification ratio was $100.24{\pm}4.68%$. This Diffrerence is attributed mainly to the ill defined cephalometric landmarks, not to the positional change of the dry skull. 3. Cephalometric measurement of lateral and frontal radiographs had no consecutive magnification ratio because of the different focus-object distance. The mean difference between the frontal and lateral cephalogram to the actual lineal measurements was $4.72{\pm}2.01mm$ and $-5.22{\pm}3.36mm$. Vertical measurements were slightly more accurate than horizontal measurements. 4. Applying to the actual patient analysis, it is recommendable to use this program for analyzing the asymmetry or spatial change after operation. The orthodontic bracket would be a favorable cephalometric landmark for constructing the three dimensional images.

• The korean journal of orthodontics
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• v.19 no.3
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• pp.113-122
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• 1989

About twenty years ago the computer was introduced into orthodontic, but not in clinics because it was inconvenient in cost, size, capacity and operation. But recent advances in the technology of electronics have produced a personal computer which is suitable for use in clinics. We have developed useful program for cephalometric Ax, model analysis and patient management. The computer program greatly aided in saving time & effort and performed well in the management & searching for patient data. But further studies about three dimensional analysis, S.T.O. and derivation of automatic treatment planning from analysis are needed.

• Journal of Yeungnam Medical Science
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• v.18 no.1
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• pp.123-137
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• 2001

Background: The purpose of this study is to evaluate the accuracy of measurements obtained from 3-dimensional computerized tomography and 3-dimensional cephalogram constructed by using the frontal and lateral cephalogram of six human dry skulls. Materials and Methods: After CT scans and each cephalograms were taken, 3-dimensional coordinates (X, Y, Z) of landmarks were obtained using computer programs. In this study, the accuracy of both methods were determined by means of 14 linear measurements compare with caliper measurements. Results: The standard deviation of landmarks of 3-dimensional CT and 3-dimensional cephalogram were 0.23 mm, and 0.30 mm in X axis, 0.27 mm and 0.25 mm in Y axis, and 0.27 mm and 0.31 mm in Z axis. In both methods, the standard deviation were less than 0.5 mm in all landmarks, and the most of landmarks showed less than 1 mm in range. Concerning the accuracy, the mean difference between 3-dimensional CT and manual measurements was 0.33 mm, and 1.13 mm between 3-dimensional cephalogram and manual measurements. The distance between RGo and LGo showed the largest difference (2.03 mm). There were highly significant, and large correlation with manual measurements in both methods (p<0.01). Conclusion: It is concluded that closeness of repeated measures to each skulls reveal the precision of both methods. Computerized tomography and cephalogram for 3-dimensional measurement of maxillofacial structure are equivalent in quality to caliper measurements.

• The korean journal of orthodontics
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• v.32 no.1 s.90
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• pp.59-69
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• 2002

The purpose of this study was to evaluate the reproducibility of lateral cephalometric landmarks according to radiographic image enhancement, and to contribute to the identification of cephalometric landmarks. Lateral cephalograms of ten individuals were taken and stored into computer. The images were then enhanced up to four grades by Quick Ceph Image Pro$^{TM}$ on condition that the gray-scale equalization number was 50 and the detail enhancement number was 50. After thirty two landmarks were identified on monitor images by five observers, the deviations from the mean, the distances estimated between identified points and the mean point of five identified points, were evaluated for each landmark at each enhancement grade. Through the statistical analysis, following results were obtained. 1. In case of unenhanced radiographic images, the inter-observer reproducibility of the landmarks showed a large variation. 2. The comparison of deviation from the mean according to the degree of radiographic image enhancement for each landmark showed that the inter-observer reproducibility was significantly different at 5 landmarks. 3. The landmark of pterygomaxillary fissure showed higher reproducibility at enhancement grade 1 and 2 images than at unenhanced images. So did the landmark of posterior nasal spine at enhancement grade 1 images, and the landmark of menton at enhancement grade 2, 3 and 4 images respectively. The above results suggest that the reproducibility of some landmarks can be increased by radiographic image enhancement during the identification of the lateral cephalometric landmarks on the monitor.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.24 no.2
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• pp.347-359
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• 1994

The reproducibility of cephalography in repeated exposures were studied by tracing and photographic subtraction. The materials consisted of 50 pairs of 'same day' radiograph taken under identical conditions. The evaluation included skull, cervical column, hyoid bone, pharynx, tongue, soft tissue profile resulting 43 items in tracing, and 19 items in photographic subtraction. The results obtained from the differences between each pair were as follows: 1. The means and standard deviations by tracing of skull, cervical column, hyoid bone, pharynx, tongue, soft tissue profile were 0.34±0.62㎜, 1.02±1.59㎜, 1.37±1.78㎜, 0.55±1.16㎜, 0.51±1.51㎜, 0.15±0.3㎜ each. 2. The means and standard deviations by photographic subtraction of skull, cervical column, hyoid bone, pharynx, tongue were 0.09±0.35㎜, 0.70±0.95㎜, 1.22±1.33㎜, 0.53±0.86㎜, 0.27±0.41㎜ each.