Use of Head Posture Aligner to improve accuracy of frontal cephalograms generated from cone-beam CT scans / 대한치과교정학회지

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.

A comparative study of guiding methods for natural head posture in cephalometrics / 대한치과교정학회지

The purpose of this study was to compare the degree of vertical head rotation and to evaluate the reproducibility of natural head posture (NHP) according to two guiding methods, the head posture aligner (HPA) method and the self balance posture (SBP) method. The subjects consisted of 30 adults. On the first day, lateral and frontal cephalometric radiographs were obtained through the two guiding methods. One month later, lateral and frontal cephalometric radiographs were obtained again through both guiding methods. The degrees of vertical head rotation of both guiding methods were compared and the reproducibility was evaluated for each guiding method. A comparison of the degrees of vertical head rotation for the two methods revealed that the vertical head posture was lower in the SBP method than in the HPA method by an average of 2.79 degrees. All measurements obtained using the HPA and SBP methods with a time interval of one month did not show any significant difference in lateral and frontal cephalometric radiographs. The results of the present study suggest that the SBP method may be used as an alternative to the HPA method in case the HPA method can not be applied.

The validity of head posture aligner in posteroanterior cephaiometry / 대한치과교정학회지

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 degrees in the HPA method, more less than 2.5 degrees 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.