A DEVELOPMENT OF 3 DIMENSIONAL CEPHALOMETRIC ANALYSIS SYSTEM

Lee, Sang Han; Kwon, Tae Geon; Kim, Jong Bae

Abstract

Diagnosis of dentofacial deformity needs three dimensional comprehensive understanding of craniofacial skeleton. Eventhough three dimensional computerized tomogram has been developed, the quantified measurement analysis is merely depend on cephalomeric analysis. In our pilot study using the ordinary cephalometric radiogram which is commonly used in clinical basis, we tried to reconstruct three dimensional coordinates from frontal and lateral cephalogram taken from five dry skulls attached with small metal ball. To evaluate the reproducibility of the cephalogram, intra-examiner error was measured and compared with the three dimensional coordinates. Fourteen linear measurement of dry skull and three dimensional value has been compared. The results were as follows: 1. The intra-examiner error of the two dimensional cephalogram showed a similar variation below 1 mm in frontal and lateral cephalogram. The error ranged from 0.11-0.13mm in the case of frontal cephalometrics and 0.12-0.57mm for lateral cephalometrics Three dimensional coordinates showed relatively high reproducibility except 7 coordinates out of 90 (7.8%). The average error of the single measurement of x,y,z point shown to be 0.04+/-0.21mm, 0.01+/-0.01mm. 0.08+/-0.08mm. 2. Compare the 14 linear measurement of dry skull and three dimensional measurement, the mean difference was 0.13+/-1.54mm, ranging from 2.59+/-3.00mm (L-Co, R-Co) to 0.01+/-0.38 (ANS, L-Or). From the result by taking real value percentage rate by 3 dimensional measuring value, the mean value was 100.74+/-3.92% and the measurement which showed the most shortening compared with the real value was the distance between R-Or and ANS (97.75+/-3.11%) and the most enlarged measurement was the distance between L-VMC, L-VIC (106.59+/-20.33%). 3. However, compare the real value and two dimensional cephalometric radiograph, difference between the two is significant degree which hinder the use of two dimensional measurement in clinical situation. This potential pitfall of the cephalogram might be overcome by using our three dimensional coordinate system. If the reproducibility of the frontal and lateral cephalogram is achieved, major concern related to the accuracy of three dimensional measurement is correct detection of anatomical landmark. Further investigation of anatomical investigation of facial skeleton will make this system more accurate and popular in clinical field.