A three-dimensional comparison of a morphometric and conventional cephalometric midsagittal planes for craniofacial asymmetry

Morphometric methods are used in biology to study object symmetry in living organisms and to determine the true plane of symmetry. The aim of this study was to determine if there are clinical differences between three-dimensional (3D) cephalometric midsagittal planes used to describe craniofacial asymmetry and a true symmetry plane derived from a morphometric method based on visible facial features. The sample consisted of 14 dry skulls (9 symmetric and 5 asymmetric) with metallic markers which were imaged with cone-beam computed tomography. An error study and statistical analysis were performed to validate the morphometric method. The morphometric and conventional cephalometric planes were constructed and compared. The 3D cephalometric planes constructed as perpendiculars to the Frankfort horizontal plane resembled the morphometric plane the most in both the symmetric and asymmetric groups with mean differences of less than 1.00 mm for most variables. However, the standard deviations were often large and clinically significant for these variables. There were clinically relevant differences (>1.00 mm) between the different 3D cephalometric midsagittal planes and the true plane of symmetry determined by the visible facial features. The difference between 3D cephalometric midsagittal planes and the true plane of symmetry determined by the visible facial features were clinically relevant. Care has to be taken using cephalometric midsagittal planes for diagnosis and treatment planning of craniofacial asymmetry as they might differ from the true plane of symmetry as determined by morphometrics

Application of cone beam computed tomography in 3D cephalometry

Chapter 1 Cone beam computed tomography (CBCT) imaging has had a tremendous impact on the practice of orthodontics and craniofacial surgery since its inception almost a decade ago. However, the limitatoons and pitfalls regarding this imaging method should be addressed in order to fully appreciate and correctly apply the possibilities that CBCT imaging offers. In all aspects of CBCT imaging, from utilization to application, inherent limitations and pitfalls exist. The general and specific research aims of this thesis were formulated to address the following issues regarding the limitations of CBCT as an imaging modality: In order to make valid conclusions from cephalometric measurements, the measurement error should be determined at a level that can detect significant differences (a = 0.05). Therefore, the smallest detectable difference or SDD (95% confidence interval of the measurement error) should be determined. The clinical relevance of the SDD in cephalometry is that the measured difference between two observations must be at least equal or larger than the SDD in order to be regarded as real change. This importance of the SDD in cephalometry is seldom realized. CBCT imaging still exposes the patient to more radiation than conventional cephalograms. Therefore, current guidelines do not support CBCT imaging as routine modality for orthodontic practice. However, some differences regarding interpretation of current utilization guidelines of CBCT imaging in orthodontics exist. This is especially true for the new applications of 3D images which are not possible with traditional radiography. Developing clear, yet evidence-based selection criteria for CBCT imaging in orthodontics is therefore needed, not only to guarantee safe use of the technology but to ultimately improve patient management. Technical difficulties of CBCT start with the positioning of the patient prior to the scanning procedure. To avoid distortion and movement artifacts due to the long scanning times of CBCT, the head of the patient is often fixed which makes capturing the head in the natural head position (NHP) difficult. Because the NHP has become an indispensible method to appraise the head due to its stability, methods and techniques to achieve a NHP of the head for CBCT imaging should be investigated. To overcome problems associated with 2D methods, 3D planning of craniofacial surgery by means of computer-aided surgery simulation of CBCT-derived surface models has been proposed.

Comparison between two-dimensional and midsagittal three-dimensional cephalometric measurements of dry human skulls

The aim of this study was to compare two- and three-dimensional cephalometric values by using a three-dimensional analysis based on the midsagittal plane. Spherical metal markers were fixed on to the anatomical landmarks of 10 human skulls, which were examined radiographically with conventional lateral cephalograms and cone-beam computed tomographic (CBCT) scans. Preprogrammed analyses calculated the 18 angular and linear two- and three-dimensional cephalometric values. An error study was made to assess the accuracy and reliability of the methods used. Both sets of values were compared using Wilcoxon's signed-rank test. Probabilities of less than 0.05 were accepted as significant. Reliability of the measurements was assessed by intraclass correlation coefficients (ICC) based on absolute agreement. The method error (ME) was tiny (mean ME<0.61 measuring unit) and reliable (ICC>0.97). Comparison of the two- and three-dimensional measurements showed that that they were reliable (ICC>0.88) and that there were no significant differences (P=0.41-1.00). The values from the cephalometric analyses were comparable and interchangeable when using the midsagittal three-dimensional approach as described

Application of cone beam computed tomography in facial imaging science

The use of three-dimensional (3D) methods for facial imaging has increased significantly over the past years. Traditional 2D imaging has gradually being replaced by 3D images in different disciplines, particularly in the fields of orthodontics, maxillofacial surgery, plastic and reconstructive surgery, neurosurgery and forensic sciences. In most cases, 3D facial imaging overcomes the limitations of traditional 2D methods and provides the clinician with more accurate information regarding the soft-tissues and the underlying skeleton. The aim of this study was to review the types of imaging methods used for facial imaging. It is important to realize the difference between the types of 3D imaging methods as application and indications thereof may differ. Since 3D cone beam computed tomography (CBCT) imaging will play an increasingly important role in orthodontics and orthognathic surgery, special emphasis should be placed on discussing CBCT applications in facial evaluations

Practical limitations of cone-beam computed tomography in 3D cephalometry

3D cone beam computed tomography (CBCT) images offer a unique and new appreciation of the anatomical structures and underlying anomalies not possible with conventional radiographs. However, in almost all aspects of CBCT imaging, from utilization to application, inherent limitations and pitfalls exist. Importantly, these inherent limitations and pitfalls have practical implications which need to be addressed before the potential of this technology can be fully realized. The purpose of this review was to explore the current limitations and pitfalls associated with CBCT imaging to allow for better and more accurate understanding of the possibilities this imaging modality could offer, particularly pertaining to 3D cephalometry