الفهرس 
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Abstract
Over the past century, craniometric measurements have been considered of great significance in the field of dentistry especially in the field of orthodontics and orthognathic surgery. Dental researchers have been thriving to innovate new methods for obtaining precise radiographic measurements, since the accuracy and reliability of linear and angular measurements of the jaws is mandatory for planning of different dental procedures. Therefore, it is of vital importance to assess the accuracy and reliability of different radiographic techniques.
The present study was conducted on twelve dry human skulls to evaluate the reliability of linear and angular measurements obtained from CBCT and cephalometric radiography compared to direct skull measurements (gold standard).
Materials and Methods:
Fifteen anatomical landmarks were identified on each dry skull, gutta- percha pieces were glued to the selected landmarks. Ten linear measurements were taken between the identified landmarks using a digital caliper, and two angular measurements were obtained using a goniometer. These direct measurements were considered as the gold standard.
The skulls were covered with 10 layers of pink modelling wax to provide an average thickness of about 13-17 mm to simulate soft tissue attenuation, then the twelve skulls were subjected to digital lateral and posteroanterior cephalometric examination using Sirona ORTHOPHOS panoramic and cephalometric X ray machine. The acquired data was transferred into SIDEXIS XG software. In addition, the twelve skulls were radiographed using
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Scanora 3Dx Cone Beam Computed Tomography scanner (CBCT), then the acquired data was exported into On Demand 3D application software for image analysis and measurements.
Results from the direct skull linear and angular measurements and those obtained from cephalometry, CBCT 2D MPR and CBCT 3D VR were compared and correlated to assess the accuracy and reliability of these imaging techniques.
Results:
The results of the current study showed very good intra-observer and inter- observer reliability regarding all the assessed linear and angular measurements obtained from gold standard, cephalometry and CBCT scans.
Regarding linear measurements, cephalometry revealed overestimated values in relation to the gold standard in all assessed distances, on the other hand, all measurements obtained from CBCT showed underestimated values compared to the gold standard except for the (N-Me) distance in 2D MPR and the nasal height (N-ANS) in 3D VR. Both showed non significant overestimated value in comparison to the gold standard. Moreover, CBCT-2D showed the highest correlation with the GS followed by CBCT-3D, while cephalometry revealed the lowest correlation.
Regarding angular measurements, for the gonial angle; cephalometry, CBCT 2D MPR and CBCT 3D VR showed non-significant underestimated values in relation to gold standard, while for the AGR-Me-AGL angle; cephalometry showed significant overestimated value, on the other hand, CBCT (2D MPR and 3D VR) showed non-significant underestimated values in relation to GS. In addition, both CBCT-2D and CBCT-3D showed high
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correlation with the GS regarding both angles assessed. However,
cephalometry showed the lowest correlation regarding AGR-Me-AGL angle,
while cephalometry showed high correlation with GS concerning the gonial
angle.
Regarding the comparison between the accuracy of CBCT linear and
angular measurements obtained from 2D MPR images to those obtained from
3D images, of the 10 linear measurements assessed in the current study, CBCT
2D MPR showed statistical difference in three measurements, while in CBCT
3D VR, four measurements showed statistical difference in comparison to the
gold standard.
Moreover, regarding both angles assessed in the present study, CBCT 3D
VR showed slightly higher mean error than CBCT 2D MPR in relation to the
gold standard.
Conclusions
from the results of the present study, the following conclusions could be
drawn:
1- Linear and angular measurements obtained from CBCT (2D MPR and
3D VR) are highly accurate and reliable and can be confidently used for
different maxillofacial clinical applications especially in orthodontics.
2- Although cephalometry demonstrates lower accuracy in comparison to
CBCT, it is still considered the gold standard for orthodontic follow-up
and evaluation of treatment outcome.
3- CBCT linear and angular measurements obtained from 2D MPR images
are relatively more accurate than those obtained from 3D VR images.