• 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.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.

• 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.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.

• 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.

• Imaging Science in Dentistry
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• v.47 no.2
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• pp.93-97
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• 2017

Purpose: The purpose of this study was to evaluate the accuracy of panoramic imaging in measuring the right and left gonial angles by comparing the measured angles with the angles determined using a lateral cephalogram of adult patients with class I malocclusion. Materials and Methods: The gonial angles of 50 class I malocclusion patients (25 males and 25 females; mean age: 23 years) were measured using both a lateral cephalogram and a panoramic radiograph. In the lateral cephalograms, the gonial angle was measured at the point of intersection of the ramus plane and the mandibular plane. In the panoramic radiographs, the gonial angle was measured by drawing a line tangent to the lower border of the mandible and another line tangent to the distal border of the ascending ramus and the condyle on both sides. The data obtained from both radiographs were statistically compared. Results: No statistically significant difference was observed between the gonial angle measured using the lateral cephalograms and that determined using the panoramic radiographs. Further, there was no statistically significant difference in the measured gonial angle with respect to gender. The results also showed a statistically insignificant difference in the mean of the right and the left gonial angles measured using the panoramic radiographs. Conclusion: As the gonial angle measurements using panoramic radiographs and lateral cephalograms showed no statistically significant difference, panoramic radiography can be considered in orthodontics for measuring the gonial angle without any interference due to superimposed images.

• 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.

• 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.

• Journal of the korean academy of Pediatric Dentistry
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• v.44 no.2
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• pp.129-137
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• 2017

The aim of this study was to enhancing the panoramic radiograph's clinical use for assessing mandibular measurements and formulating a function of those measurements from panoramic radiographs and lateral cephalograms in children. The panoramic radiographs and lateral cephalograms of 99 former orthodontic patients with skeletal class III malocclusion were selected. In each radiograph, gonial angles, ramus heights, and distance between lower incisors and symphysis were measured. The values of the studied parameters were compared by paired t-test, Pearson's correlation test and regression analysis. The mean value of the gonial angle in panoramic radiographs was $125.49^{\circ}$, and the value in lateral cephalograms was $127.50^{\circ}$. The Pearson's correlation coefficient (${\rho}$) between mean values of gonial angle in each radiograph was 0.945 (p < 0.001). The relationship between the gonial angle measurements obtained from each radiographs was represented as 'Gonial angle (Lateral cephalograms) = 0.920 ${\times}$ Average gonial angle (Panoramic radiographs) + 12.072' in the linear function. The coefficients of ramus heights, and distance between lower incisors and symphysis portrayed weaker correlations than gonial angles. A panoramic radiograph could be used to determine the gonial angle as accurately as a lateral cephalogram, and each gonial angle showed a strong positive relation. A panoramic radiograph is a useful tool for examining vertical growth pattern of patients, as well as a lateral cephalogram.

• The korean journal of orthodontics
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• v.30 no.5 s.82
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• pp.543-552
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• 2000

The purposes of this study were to evaluate the reproducibility of posteroanterior(PA) cephalograms obtained by two methods, the Head Posture Aligner(HPA) method in natural head posture and the conventional method(operator-guided method), and to compare the vertical rotational differences of the head Posture between lateral and PA cephalograms according to the method. The sample was consisted of 30 adults. At first day, a PA cephalogram and a lateral cephalogram were obtained from each subject by two methods to investigate the difference of vertical rotational posture between lateral and PA cephalograms. Two weeks later, another PA cephalogram was obtained using each method to evaluate the reproducibility of head posture. Five height measurements and nine width measurements were used in the paired t-test to compare the reproducibility of the PA cephalometric measurements between two methods. The differences of vertical rotational posture between lateral and PA cephalograms were calculated from a computer program and compared according to the method used, and following results were obtained. 1. Height measurements obtained by operator-guided method showed significant differences according to the time interval and revealed low reproducibility. 2. Height measurements obtained by HPA method did not show significant differences according to the time interval and presented high reproducibility. 3. In the comparison of width measurement, two methods did not show distinct differences in reproducibility. 4. The difference of vertical rotational posture between lateral and PA cephalograms showed $0.8^{\circ}$ in the HPA method, more less than $2.5^{\circ}$ in the operator-guided method. The results of the present study suggest that the HPA may be helpful in the PA cephalometric radiography in terms of reproducibility.