• The korean journal of orthodontics
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• v.49 no.1
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• pp.32-40
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• 2019

Objective: Precise identification of landmarks on posteroanterior (PA) cephalograms is necessary when evaluating lateral problems such as facial asymmetry. The aim of the present study was to investigate whether the use of lateral (LA) cephalograms can reduce errors in landmark identification on PA cephalograms. Methods: Five examiners identified 16 landmarks (Cg, N, ANS, GT, Me, RO, Lo, FM, Z, Or, Zyg, Cd, NC, Ms, M, and Ag) on 32 PA cephalograms with and without LA cephalograms at the same time. The positions of the landmarks were recorded and saved in the horizontal and vertical direction. The mean errors and standard deviation of landmarks location according to the use of LA cephalograms were compared for each landmark. Results: Relatively small errors were found for ANS, Me, Ms, and Ag, while relatively large errors were found for N, GT, Z, Or, and Cd. No significant difference was found between the horizontal and vertical errors for Z and Or, while large vertical errors were found for N, GT, and Cd. The value of identification error was lower when the landmarks were identified using LA cephalograms. Statistically significant error reductions were found at N and Cd with LA cephalograms, especially in the vertical direction. Conclusions: The use of LA cephalograms during identification of landmarks on PA cephalograms could help reduce identification errors.

• The korean journal of orthodontics
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• v.49 no.1
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• pp.41-48
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• 2019

Objective: This in-vivo study aimed to compare landmark identification errors in anteroposterior (AP) and posteroanterior (PA) cephalograms generated from cone-beam computed tomography (CBCT) scan data in order to examine the feasibility of using AP cephalograms in clinical settings. Methods: AP and PA cephalograms were generated from CBCT scans obtained from 25 adults. Four experienced and four inexperienced examiners were selected depending on their experience levels in analyzing frontal cephalograms. They identified six cephalometric landmarks on AP and PA cephalograms. The errors incurred in positioning the cephalometric landmarks on the AP and PA cephalograms were calculated by using the straight-line distance and the horizontal and vertical components as parameters. Results: Comparison of the landmark identification errors in CBCT-generated frontal cephalograms revealed that landmark-dependent differences were greater than experienceor projection-dependent differences. Comparisons of landmark identification errors in the horizontal and vertical directions revealed larger errors in identification of the crista galli and anterior nasal spine in the vertical direction and the menton in the horizontal direction, in comparison with the other landmarks. Comparison of landmark identification errors between the AP and PA projections in CBCT-generated images revealed a slightly higher error rate in the AP projections, with no inter-examiner differences. Statistical testing of the differences in landmark identification errors between AP and PA cephalograms showed no statistically significant differences for all landmarks. Conclusions: The reproducibility of CBCT-generated AP cephalograms is comparable to that of PA cephalograms; therefore, AP cephalograms can be generated reliably from CBCT scan data in clinical settings.

• Imaging Science in Dentistry
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• v.51 no.4
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• pp.407-412
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• 2021

Purpose: The purpose of this study was to evaluate the accuracy of virtual 3-dimensional (3D) cephalograms constructed using the principle of biplanar radiography by comparing them with cone-beam computed tomography (CBCT) images. Materials and Methods: Thirty orthodontic patients were enrolled in this study. Frontal and lateral cephalograms were obtained with the use of a head posture aligner and reconstructed into 3D cephalograms using biplanar radiography software. Thirty-four measurements representing the height, width, depth, and oblique distance were computed in 3 dimensions, and compared with the measurements from the 3D images obtained by CBCT, using the paired t-test and Bland-Altman analysis. Results: Comparison of height, width, depth, and oblique measurements showed no statistically significant differences between the measurements obtained from 3D cephalograms and those from CBCT images (P>0.05). Bland-Altman plots also showed high agreement between the 3D cephalograms and CBCT images. Conclusion: Accurate 3D cephalograms can be constructed using the principle of biplanar radiography if frontal and lateral cephalograms can be obtained with a head posture aligner. Three-dimensional cephalograms generated using biplanar radiography can replace CBCT images taken for diagnostic purposes.

• The korean journal of orthodontics
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• v.27 no.1
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• pp.129-140
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• 1997

Conventional cephalometrics have inherent errors because their evaluation is performed in two-dimension for threedimensional object. To compensate these errors, three-dimensional cephalograms - derivation of three-dimensional data from conventional lateral and postero-anterior cephalograms - were developed. In this study, the accuracy and precision of three dimensional cephalograms were determined by means of 10 linear and 12 angular measurements on 36 acrylic skull models and by the comparison of conventional lateral cephalograms. The results were as follows 1. Mean difference between three-dimensional cephalograms and actual models in linear measurements was $0.94{\pm}0.62mm$ and mean rate of magnification of three-dimensional cephalograms was $100.31{\pm}0.91%$. There were no statistically significant differences between three-dimensional cephalograms and actual models in linear measurements(${\alpha}=0.1$). 2. Mean difference between conventional lateral cephalograms and actual models in linear measurements was $6.44{\pm}1.48mm$ and mean rate of magnification of lateral cephalograms was $106.99{\pm}1.45%$. There were statistically significant differences between lateral cephalograms and actual models in linear measurements(P<0.005). 3. Mean difference between three-dimensional cephalograms and actual models in angular measurements was $1.22{\pm}0.82^{\circ}$ and mean rate of magnification of three-dimensional cephalograms was $105.71{\pm}12.07%$. There were no statistically significant differences between three-dimensional cephalograms and actual models in angular measurements(${\alpha}=0.1$). 4. Mean difference between conventional lateral cephalograms and actual models in angular measurements was $1.70{\pm}0.94^{\circ}$ and mean rate of magnification of lateral cephalograms was $106.35{\pm}15.70%$. There were no statistically significant differences between lateral cephalograms and actual models in angular measurements(${\alpha}=0.1$). There were similarity between three-dimensional and lateral cephalograms in angular measurements.

• The korean journal of orthodontics
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• v.39 no.5
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• pp.289-299
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• 2009

Objective: The purpose of the present study was to evaluate the effectiveness of the use of Head Posture Aligner (HPA) during cone-beam computed tomography (CBCT) scan in generation of frontal cephalograms using 3D CBCT images. Methods: CBCT scans and frontal cephalograms were made in 30 adult individuals. While a couple of CBCT scan was made for one subject, one was made with conventional method, without use of HPA, the other was acquired with the use of HPA. After creation of virtual frontal cephalogram from each 3D CBCT image, it was traced and compared with the tracing of real frontal cephalogram. Results: In the comparison of the measurements, the virtual cephalograms with the use of HPA did not show statistically significant differences with the real cephalograms whereas the virtual cephalograms without the use of HPA presented significant differences with real cephalograms in many measurements. In the correlation analysis with the measurements of the real cephalograms, the virtual cephalograms with the use of HPA showed higher correlations in all measurements than the virtual cephalograms without the use of HPA. Conclusions: Measurements from CBCT-generated cephalograms become similar to those from real cephalograms with the use of HPA during CBCT scan. Thus, the use of HPA is suggested during the CBCT scan in order to construct accurate virtual frontal cephalograms using 3D CBCT images.

• The korean journal of orthodontics
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• v.43 no.2
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• pp.54-61
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• 2013

Objective: The purpose of this study was to evaluate the effectiveness of the use of Reference Ear Plug (REP) during cone-beam computed tomography (CBCT) scan for the generation of lateral cephalograms from CBCT scan data. Methods: Two CBCT scans were obtained from 33 adults. One CBCT scan was acquired using conventional methods, and the other scan was acquired with the use of REP. Virtual lateral cephalograms created from each CBCT image were traced and compared with tracings of the real cephalograms obtained from the same subject. Results: CBCT scan with REP resulted in a smaller discrepancy between real and virtual cephalograms. In comparing the real and virtual cephalograms, no measurements significantly differed from real cephalogram values in case of CBCT scan with REP, whereas many measurements significantly differed in the case of CBCT scan without REP. Conclusion: Measurements from CBCT-generated cephalograms are more similar to those from real cephalograms when REP are used during CBCT scan. Thus, the use of REP is suggested during CBCT scan to generate accurate virtual cephalograms from CBCT scan data.

• The korean journal of orthodontics
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• v.48 no.5
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• pp.292-303
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• 2018

Objective: Biplanar imaging systems allow for simultaneous acquisition of lateral and frontal cephalograms. The purpose of this study was to compare measurements recorded on three-dimensional (3D) cephalograms constructed from two-dimensional conventional radiographs and biplanar radiographs generated using a new biplanar imaging system with those recorded on cone-beam computed tomography (CBCT)-generated cephalograms in order to evaluate the accuracy of the 3D cephalograms generated using the biplanar imaging system. Methods: Three sets of lateral and frontal radiographs of 15 human dry skulls with prominent facial asymmetry were obtained using conventional radiography, the biplanar imaging system, and CBCT. To minimize errors in the construction of 3D cephalograms, fiducial markers were attached to anatomical landmarks prior to the acquisition of radiographs. Using the 3D $Ceph^{TM}$ program, 3D cephalograms were constructed from the images obtained using the biplanar imaging system (3D $ceph_{biplanar}$), conventional radiography (3D $ceph_{conv}$), and CBCT (3D $ceph_{cbct}$). A total of 34 measurements were obtained compared among the three image sets using paired t-tests and Bland-Altman plotting. Results: There were no statistically significant differences between the 3D $ceph_{biplanar}$ and 3D $ceph_{cbct}$ measurements. In addition, with the exception of one measurement, there were no significant differences between the 3D $ceph_{cbct}$ and 3D $ceph_{conv}$ measurements. However, the values obtained from 3D $ceph_{conv}$ showed larger deviations than those obtained from 3D $ceph_{biplanar}$. Conclusions: The results of this study suggest that the new biplanar imaging system enables the construction of accurate 3D cephalograms and could be a useful alternative to conventional radiography.

• Imaging Science in Dentistry
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• v.42 no.4
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• pp.201-205
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• 2012

Purpose: This study was performed to assess the compatibility of cone beam computed tomography (CBCT) synthesized cephalograms with conventional cephalograms, and to find a method for obtaining normative values for three-dimensional (3D) assessments. Materials and Methods: The sample group consisted of 10 adults with normal occlusion and well-balanced faces. They were imaged using conventional and CBCT cephalograms. The CBCT cephalograms were synthesized from the CBCT data using OnDemand 3D software. Twenty-one angular and 12 linear measurements from each imaging modality were compared and analyzed using paired-t test. Results: The linear measurements between the two imaging modalities were not statistically different (p>0.05) except for the U1 to facial plane distance. The angular measurements between the two imaging modalities were not statistically different (p>0.05) with the exception of the gonial angle, ANB difference, and facial convexity. Conclusion: Two-dimensional cephalometric norms could be readily used for 3D quantitative assessment, if corrected for lateral cephalogram distortion.

• Imaging Science in Dentistry
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• v.52 no.3
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• pp.295-302
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• 2022

Purpose: Lateral cephalograms of orthodontic patients may contain incidental findings that could potentially lead to harm. Materials and Methods: The lateral cephalograms of 1765 consecutive 12- to 20-year-old patients, being considered for routine orthodontic treatment, were retrospectively reviewed. These patients were considered normal, because no abnormalities were found either in their medical history or on their clinical examination. Results: The overall prevalence of incidental findings was 18.8%, of which 10.3% were ponticulus posticus and 4.2% were bridging of the sella turcica. Although occipital spurs and ponticulus posticus were more prevalent in males, the size of the sella turcicas did not differ between sexes. Of the 1156 patients completing treatment about 2 years later, only one lateral cephalogram displayed progression of the ponticulus posticus in that time. Conclusion: The prevalence of incidental findings on lateral cephalograms of otherwise normal orthodontic 12- to 20-year-old patients was almost a fifth, of which ponticulus posticus, vertebral fusion, and enlarged parietal foramina were clinically significant.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.18 no.4
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• pp.594-606
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• 1996

This study was intended to perform the relationships between mandibualr lateral deviation in facial asymmetry patients and morphology of the cranial vault. In 30 patients(males 14, female 16) using submento-vertical cephalograms that were taken in the pre-operaticve state and posteroanterioir cephalograms that were taken in centric occlusion before, immediate and long term after surgery. 1. Mean mandibular deviation was about $-3.12^{\circ}$and mean of absolute measurement was about $2.50^{\circ}$on the submento-vertical cephalograms. 2. On the submento-vertical cephalograms, there was no significant difference between non-deviation and deviation side but it had tendency that deviation side was larger than non-deviation side on the frontal portion of cranium(Y10 to Y6) and deviation side was smaller than non-deviation on the temporal portion of cranium(Y5, Y-1 to Y-5). 3. Mean mandibular deviation was about $1.40^{\circ}$and mean of absolute measurement was about $3.95^{\circ}$on the posteroanterioir cephalograms. 4. There was statistical significance on the influence of surgical change(PT2A-PT1A) to the relapse(PTLA-PT2A)(p<0.05). The more increasing of the change, the more relapse on the posteroanterioir cephalograms. 5. There was no statistical significance on the influence of degree of mandibular deviation to morphology of the cranium on the submento-vertical cephalograms. But it had tendency that the more mandibular deviation, the larger the non-deviation side on the anterior cranium and deviation side on the posterior cranium(p>0.05). 6. There was statistical significance on the influence of the degree of mandibular deviation on the posteroanterioir cephalograms to the difference between non-deviation and deviation side. The more increasing of mandibular deviation, the larger the non-deviation side on the Y4 to Y-6(p<0.05). 7. There was no statistical significance on the influence of difference between non-deviation and deviation side to the relapse on the posteroanterioir cephalograms. But it had tendency that the more increasing of the differece between non-deviation and deviation side, the more increasing the relapse on temporal of cranium.