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When observing the high financial outlay for a cone beam device, prudent practitioners should determine how often they would use the device in their practices. Typical current fees for cone beam imaging in the U.S. Range from $150 to $700, and if needed, scans by an oral and maxillofacial radiologist are about $65 to $75.
Dental Press J Orthod. 2015 Mar-Apr; 20(2): 83–89.
PMID: 25992992
Language: English | Portuguese
Abstract
INTRODUCTION:
One of the advantages of cone-beam computed tomography (CBCT) is the possibilityof obtaining images of conventional lateral cephalograms derived from partial orcomplete reconstruction of facial images.
OBJECTIVE:
This study aimed at comparing full face, right and left hemifacial CBCTcephalograms of orthodontic patients without clinical facial asymmetry.
METHODS:
The sample comprised nine clinically symmetrical patients who had pretreamentfull face CBCT. The CBCTs were reconstructed so as to obtain full face, right andleft hemifacial cephalograms. Two observers, at two different times, obtainedlinear and angular measurements for the images using Dolphin 3D software.Dependent and independent t-tests were used to assess the reproducibility ofmeasurements. Analysis of Variance and Kruskal-Wallis tests were used to comparethe variables obtained in the CBCT derived cephalometric views.
RESULTS:
There was good reproducibility for CBCT scans and no statistically significantdifferences between measurements of full face, right and left hemifacial CBCTscans.
CONCLUSIONS:
Cephalometric measurements in full face, right and left hemifacial CBCT scans inclinically symmetrical patients are similar.
Keywords: Cone-beam computed tomography, Facial asymmetry, Diagnosis, Orthodontics
Abstract
INTRODUÇÃO:
uma das vantagens da tomografia computadorizada de feixe cônico (TCFC) é apossibilidade de obtenção da imagem da telerradiografia em norma lateralconvencional, por reconstruir parcial ou totalmente a face em uma visão sagital.
OBJETIVO:
o presente estudo teve como objetivo comparar as imagens de cefalogramas obtidasda face total e das hemifaces direita e esquerda por meio de TCFC, em pacientessem assimetria clinica.
MÉTODOS:
a amostra foi composta por nove pacientes, clinicamente simétricos, que tinham emseus prontuários TCFC de face total. Os exames tomográficos foram reformatadospara a obtenção de cefalogramas de face total e hemifaces direita e esquerda. Doisobservadores, em dois momentos diferentes, obtiveram medidas lineares e angularesdessas imagens, utilizando o software Dolphin 3D. Testest dependentes e independentes foram utilizados para verificara reprodutibilidade das medidas nas imagens. Análise de variância (ANOVA) e oteste de Kruskal-Wallis foram utilizados para comparar as variáveis obtidas nasanálises cefalométricas.
RESULTADOS:
houve boa reprodutibilidade para as imagens de TCFC e não houve diferençaestatisticamente significante entre as medidas cefalométricas obtidas decefalogramas de face total, hemifaces direita e esquerda.
CONCLUSÕES:
medidas cefalométricas obtidas de cefalogramas de face total, hemifaces direita eesquerda em pacientes clinicamente simétricos são semelhantes.
INTRODUCTION
In the last decades, three-dimensional images have contributed to diagnosis in severalfields, including Dentistry. Particularly Orthodontics can benefit from the advantagesof cone-beam technology, a new type of computed tomography (CT) with a conic shape X-raybeam.
Different from the traditional spiral CT, in which a fan-beam carries out severalrotations around the patient, with cone-beam computed tomography (CBCT) a singlerotation of x-rays and a solid panel sensor around the patient complete the exam. CBCTradiation dose is remarkably lower than spiral CT. It corresponds approximately to the effective dose generated for apanoramic, lateral x-ray and full-mouth periapical radiograph combined.,
In the CBCT exam, the field of view (FOV) can be adjusted to scan small or large areas,such as local impacted teeth and surrounding structures, or a complete face, in cases ofinitial diagnosis and treatment planning. Besides generating slices in all three planesof space, CBCT has the possibility to reconstruct two-dimensional images, such aspanoramic or lateral cephalometric radiographs. The new technology leaves behind most ofconventional x-ray disadvantages, including distortion, magnification andsuperimposition.
Previous studies validated CBCT cephalogram images for two-dimensional dentofacialevaluation., Kumar et al, aiming to compare conventional lateral and CBCT cephalograms of ten dryskulls, found that CBCT reproduced conventional cephalometric radiographs with similarprecision and accuracy. The same authors reproduced the study in 31 patients, in whichlinear and angular measurements were not statistically different for either one of themethods, except for the Frankfort mandibular plane angle. Cattaneo et al also comparedconventional cephalometric radiographs with CBCT-synthesized cephalograms of 34patients, concluding that CBCT can be successfully used to perform cephalometricanalysis. Van Vlijmen et al compared linear andangular cephalometric measurements obtained from conventional and CBCT-synthesizedcephalograms and found higher reliability for CBCT measurements and did not findsignificant differences between the two types of images. Chien et al compared the reliability of landmarkidentification in conventional cephalometric radiographs and CBCT 3D derived images andfound lower intraobserver reliability for two-dimensional than for three-dimensionalimages.
Diagnosis and treatment planning for asymmetric patients is a considerable challenge inOrthodontics. Many studies have emphasized the applicability of 3D CT scans in thesepatients, with some authors recommending their own 3D cephalometric analyses., Measuring face asymmetries usingtwo-dimensional cephalograms could be possible instead of using 3D reconstructions,which is more complex than the usual 2D cephalometry.
An important advantage of CBCT-derived cephalograms is the possibility to separatelyreconstruct the right and left sides of the face. Comparing one side to the other couldbring relevant information about asymmetries location and size. This comparison isvaluable, since eventual differences between both sides are not expected from symmetricpatients.
No previous study compared the left and right side by means of CBCT-reconstructedcephalograms to assure whether there is equivalence of both sides in clinicallysymmetric patients. For this reason, the main purpose of this pilot study was to compareright and left CBCT-derived cephalograms of clinically symmetric orthodontic patientswith full face CBCT-derived cephalograms.
MATERIAL AND METHODS
This study was approved by the Institutional Review Board of Universidade Veiga deAlmeida under protocol #157/09. The sample comprised nine orthodontic patients (sixfemales and three males) with mean age of 37.5 years. Selection criteria included:absence of clinically relevant facial asymmetry, CBCT scan as part of initialorthodontic records and age greater than sixteen years old. All nine patients had soughtorthodontic treatment exclusively due to dental malocclusion.
All CBCT scans were acquired on an iCAT Cone-Beam 3-D System (Imaging SciencesInternational, LLC, Hatfield, Penn., USA) using a field of view of 22 cm (extendedprotocol) and voxel size of 0.4 mm. Using Dolphin 3D software (Dolphin Imaging andManagement Solutions, Chatsworth, CA, USA), the CBCT scan of each patient wasreconstructed to obtain three different images: a conventional cephalogram including thecomplete width of the face (Fig 1A); a lateralcephalogram, including only the right side of the face (Fig 1B); and a lateral cephalogram, including only the left side of the face(Fig 1C). Maximum intensity of projection (MIP)was selected for CBCT image visualization. In order to include all midsagittalstructures, the reference used to limit hemifacial cephalogram reconstructionscorresponded to the incisal edge midpoint of the maxillary central incisor of theopposite side. No patient had expressive maxillary midline deviation. Images werede-identified before evaluation.
Different modalities of CBCT-derived cephalograms from the same subject A)Full face cephalogram. B) Right hemifacial cephalogram. C) Left hemifacialcephalogram.
Eleven cephalometric measurements were obtained on the cephalograms by means of Dolphin3D software (Table 1). Measurements wereperformed by two previously calibrated examiners, in two different moments, within atwo-week interval. After landmark identification, the software automatically measuredall variables.
Table 1 -
Cephalometric measurements | Definitions |
---|---|
Linear measurements (mm) | |
Maxillary length (Co-A) | Distance between Co and A |
Anterior facial height (ANS-Me) | Distance between NS and Me |
Mandibular length (Co-Gn) | Distance between Co and Gn |
Cranial base (SN) | Distance between S and N |
Angular measurements (degrees) | |
ANB | Angle formed by landmarks A, N and B |
SNA | Angle formed by landmarks S, N and A |
SNB | Angle formed by landmarks S, N and B |
SNGoGn | Angle formed by S-N line and GoGn plane |
FMA | Angle formed by Frankfort and GoMe planes |
1.PP | Angle formed by the long axis of the mostanterior maxillary central incisor and the palatal plane |
IMPA | Angle formed by the long axis of the mostanterior mandibular central incisor and the GoMe plane |
Error of the method
Intra and interexaminer reproducibility of CBCT cephalograms was tested with dependentand independent t-tests, respectively, using the values obtained for all three differentmodalities of cephalograms. Intraexaminer error was calculated using the first andsecond values obtained by the examiners. As for interexaminer error analysis, only thefirst measurements of each examiner were used.
Statistical analyses
Data normality was checked by Shapiro-Wilk test. Variables SN, ANB, SNA, SNB, FMA and1.PP showed normal distribution, thus, intergroup comparison was performed with Analysisof Variance. Variables Co-A, ANS-Me, Co-Gn, SNGoGn and IMPA did not show normaldistribution, thus, intergroup comparison was performed with Kruskal-Wallis test. Dataused for analysis were those obtained by examiner 1, at time point 1. Results wereconsidered statistically significant at P < 0.05. All statisticaltests were performed with SigmaPlot version 12.0 software (Systat Software, Inc. SanJose, California, USA).
RESULTS
There were two systematic errors for examiner 1 and four for examiner 2 (Table 2). There was only one interexaminer error(Table 3). Six out of the eleven variablesshowed casual errors lower than 1 mm or 1.5 o. Only two variables presentederrors greater than 2 mm or 2o (Tables2 and and33).
Table 2 -
Cephalometric measurement | T1 | T2 | p | Dalhberg | ||
---|---|---|---|---|---|---|
(Mean ± SD) | (Mean ± SD) | |||||
Examiner 1 | ||||||
Co-A | 84.5 ± 6.6 | 84.5 ± 6.6 | 0.937 | 0.50 | ||
ANS-Me | 68.1 ± 6.6 | 68.2 ±6.5 | 0.298 | 0.58 | ||
Co-Gn | 113.9 ± 8.2 | 113.7 ± 7.7 | 0.354 | 0.94 | ||
SN | 65.9 ± 3.7 | 66.0 ± 3.6 | 0.625 | 0.52 | ||
ANB | 2.9 ± 2.6 | 2.7 ± 2.6 | 0.150 | 0.44 | ||
SNA | 83.7 ± 3.5 | 83.5 ± 4.0 | 0.609 | 1.12 | ||
SNB | 80.8 ± 2.7 | 80.8 ± 3.5 | 0.990 | 1.03 | ||
SNGoGn | 31.6 ± 4.3 | 32.6 ± 5.8 | 0.036* | 1.82 | ||
FMA | 25.5 ± 4.4 | 26.5 ± 4.3 | 0.007* | 1.40 | ||
1.PP | 110.9 ± 8.0 | 111.3 ± 8.2 | 0.411 | 1.46 | ||
IMPA | 91.0 ± 9.8 | 90.3 ± 9.4 | 0.227 | 2.13 | ||
Examiner 2 | ||||||
Co-A | 84.6 ± 6.4 | 86.5 ± 5.9 | 0.041* | 0.99 | ||
ANS-Me | 67.2 ± 6.4 | 68.0 ± 6.0 | 0.131 | 0.33 | ||
Co-Gn | 114.1 ± 8.2 | 116.7 ± 7.4 | 0.029* | 0.79 | ||
S-N | 65.8 ± 4.0 | 66.4 ± 3.5 | 0.467 | 1.80 | ||
ANB | 3.1 ± 2.9 | 3.2 ± 2.9 | 0.850 | 0.44 | ||
SNA | 82.8 ± 3.9 | 82.7 ± 3.9 | 0.750 | 0.98 | ||
SNB | 79.7 ± 3.3 | 79.5 ± 3.5 | 0.534 | 0.85 | ||
SNGoGn | 34.4 ± 5.7 | 33.5 ± 5.6 | 0.044* | 1.12 | ||
FMA | 27.0 ± 4.3 | 26.1 ± 4.2 | 0.072 | 0.72 | ||
1.PP | 112.5 ± 8.6 | 111.0 ± 8.4 | 0.041* | 1.44 | ||
IMPA | 91.2 ± 8.8 | 89.9 ± 9.1 | 0.050 | 2.08 |
Table 3 -
Cephalometric measurement | Examiner 1 | Examiner 2 | P value | Dalhberg |
---|---|---|---|---|
Mean ± SD | Mean ± SD | |||
Co-A | 84.5 ± 6.6 | 84.6 ± 6.4 | 0.951 | 0.53 |
ANS-Me | 68.1 ± 1.2 | 67.2 ± 1.2 | 0.607 | 0.89 |
Co-Gn | 113.9 ± 8.2 | 114.1 ± 8.2 | 0.928 | 0.79 |
S-N | 65.9 ± 3.7 | 65.8 ± 4.0 | 0.912 | 1.20 |
ANB | 2.9 ± 2.6 | 3.1 ± 2.9 | 0.727 | 0.52 |
SNA | 83.7 ± 3.5 | 82.8 ± 3.9 | 0.390 | 1.31 |
SNB | 80.8 ± 2.7 | 79.7 ± 3.3 | 0.183 | 1.48 |
SNGoGn | 31.6 ± 4.3 | 34.4 ± 5.7 | 0.046* | 2.63 |
FMA | 25.5 ± 4.4 | 27.0 ± 4.3 | 0.237 | 1.57 |
1.PP | 111.3 ± 8.2 | 112.5 ± 8.6 | 0.601 | 1.95 |
IMPA | 91.0 ± 9.8 | 91.2 ± 8.8 | 0.947 | 2.35 |
No significant differences were observed among the three modalities of CBCT-synthesizedcephalograms (Table 4).
Table 4 -
Comparison of the three image modalities (Analysis of Variance andKruskal-Wallis tests).
Cephalometric measurement | Total face | Right hemiface | Left hemiface | P value | |||
---|---|---|---|---|---|---|---|
Mean ± SD | Median | Mean ± SD | Median | Mean ± SD | Median | ||
Co-A* | 84.72 ± 6.77 | 83.10 | 84.37 ± 7.03 | 82.30 | 84.48 ± 7.08 | 82.80 | 0.927 |
ANS-Me* | 68.16 ± 6.84 | 68.40 | 68.14 ± 6.87 | 68.10 | 68.08 ± 7.11 | 68.60 | 0.996 |
Co-Gn* | 114.29 ± 8.41 | 112.20 | 114.18 ± 8.51 | 111.60 | 113.48 ± 8.91 | 111.90 | 0.927 |
S-N | 65.94 ± 3.80 | 65.30 | 65.72 ± 4.17 | 65.20 | 66.26 ± 3.65 | 65.90 | 0.958 |
ANB | 2.77 ± 2.76 | 3.00 | 2.90 ± 2.67 | 3.00 | 3.06 ± 2.98 | 3.50 | 0.976 |
SNA | 83.60 ± 4.31 | 82.40 | 83.98 ± 3.39 | 83.40 | 83.64 ± 3.19 | 83.10 | 0.972 |
SNB | 80.82 ± 2.91 | 80.80 | 81.09 ± 3.09 | 81.10 | 80.59 ± 2.48 | 80.80 | 0.933 |
SNGoGn* | 31.48 ± 4.70 | 32.00 | 31.12 ± 4.08 | 29.60 | 32.22 ± 4.74 | 30.60 | 0.755 |
FMA | 25.67 ± 4.46 | 24.90 | 25.48 ± 4.45 | 25.80 | 25.56 ± 5.09 | 25.80 | 0.996 |
1.PP | 111.31 ± 7.88 | 111.40 | 111.17 ± 8.82 | 112.70 | 111.50 ± 9.05 | 112.50 | 0.997 |
IMPA* | 91.53 ± 9.06 | 95.10 | 90.29 ± 9.66 | 95.90 | 91.30 ± 11.65 | 92.00 | 0.973 |
DISCUSSION
Sample
This study was conducted based on a sample of nine orthodontic patients. Thisunpretentious number could be considered quite small to be representative. Samplereduced size is justifiable for a pilot study and was due to the inclusion criteriaregarding absence of clinical asymmetry and post adolescent age.
Nevertheless, considering the radiation dose involved in computed tomography, it is notso easy to reach a large number of patients whose conditions justify submission to theexam. Nowadays, the ethic aspects related to researches including radiation are adelicate topic of debate. To be included in this study, in addition to having a CBCTscan, the patient could not have any clinically significant asymmetry.
It is important to emphasize that CBCT exposes the patient to a greater radiation dosecompared to conventional radiographs. For thisreason, currently CBCT should only be indicated when the benefits for a better diagnosisare greater than the individual detriment that radiation exposure might cause (ALARAprinciple). On the other hand, exposure toradiation in a CBCT exam is much lower than a conventional CT. In some specific situations, when it is necessary to assessdetails on bone structures, the CBCT technology is an alternative to replace itspredecessor.
All individuals included in the present sample had a CBCT scan included in the initialorthodontic records for clinical reasons. Furthermore, the cephalograms generated helpedto elaborate their treatment plan, along with dental cast and facial analysis. If a CBCTis included in the initial orthodontic records due to specific indication, it can beused to generate 2D images. Conventional cephalogram and panoramic radiograph may beeliminated from orthodontic records, thereby considerably reducing the radiationdose.
Reproducibility of CBCT-derived cephalograms
Among the 11 cephalometric variables tested, only two showed intraexaminer systematicerror for the first examiner and four for the second examiner (Table 2). Only one variable (SNGoGn) showed significant systematicinterexaminer error (Table 3). These resultsevince the high reproducibility of cephalometric measurements in all modalities of CBCTcephalograms.
Some reproducibility error was expected because in cephalometry there are inherenterrors involved. Although a two-week intervalexisted between the two measurements, randomly or systematically, two examiners willunlikely choose, at two different moments, exactly the same point, especially those ofsubjective landmarks. Some examples are the landmarks Gonion and Gnathion, which aredifficult to identify, and may have contributed to the significant errors that appearedin SNGoGn, FMA, IMPA and Co-Gn. Gonion and Gnathion points were often involved insystematic and casual errors. Previous studies also reported higher values for errors ofmeasurements involving these points.16,17
The SNGoGn angle was involved four times in errors of reproducibility (Tables 2 and and3).3). Some arguments may explain these results. Previous studies showed thatthe fronto-nasal suture (point N) can be easily identified in CBCT scans, whereas pointSella (point S) showed lower reproducibility.8,9 Sella is identified as ageometrical center of a circular structure with the same name in the center of thesphenoid bone. Additionally, temporal bone density can slightly obstruct clearvisualization of midsagittal structures in MIP reconstructions of CBCT scans, sincestructures with higher density can hide structures of lower density.
Random errors were observed for interexaminer comparisons. Even if previouslycalibrated, two different orthodontists examiners will hardly elect the exact sameposition for a certain landmark. All but one occurrence of interexaminer errors appearedin angular measurements. Furthermore, those were all angles formed by not only three,but four points. Including one more landmark identification process each and theinexorable imprecision, they were more likely to show unavoidable casual errors.Moreover, the involvement of dental measurements, such as 1.PP and IMPA in errors, is inagreement with previous studies.17,18
The high reproducibility found for CBCT cephalometric measurements in this study is inaccordance with previous studies.8,9,19,20 Cattaneo et al found higher reproducibility for CBCT cephalogramscompared to conventional cephalometric images in a sample of 20 patients, except formeasurements NS-Ar and NS-Ba which also depend on the correct identification of point S.Chien et al compared intra and interexaminerreproducibility for 27 measurements obtained by six observers from ten conventional 2Dcephalograms and their respective CBCT-derived 3D images. The authors concluded that the3D images had improved reliability in certain landmarks in vivo whencompared with two-dimensional images. Ludlow et al compared 24 landmarks identified by five observers during two separatesections and in conventional and CBCT-derived cephalograms. CBCT scans provided moreprecise identification. The authors reported that greater variability of some points inthe mediolateral direction was probably related to inadequate definition of landmarks inthird dimension. Chang et al, comparing theidentification of 20 lateral cephalometric landmarks by 11 observers at two time points,concluded that the errors on CBCT-derived cephalograms were comparable to those onconventional digital cephalograms, and also that the Ba point was more reliable onCBCT-derived cephalograms.
Comparison between full face and hemifacial CBCT scans
There was no significant difference for any cephalometric variable in the comparisonbetween full face, right and left hemifacial CBCT scans (Table 4). Considering the absence of relevant clinical facialasymmetries in the sample, these results were expected.
No previous study compared the right and left side of CBCT-derived cephalograms.Therefore, according to the present results, right or left hemifacial CBCT cephalogramscan be used for two-dimensional cephalometry in symmetrical patients with the advantageof a clearer identification of bilateral structures. Unlike conventional cephalometricradiographs, CBCT-reformatted images have no magnification or distortions in theorthogonal plane.
One of the indications of 3D cephalometry is the assessment of patients with facialasymmetry., To locate and quantify facial asymmetry, inaddition to using 3D reformatted CBCT scans23,26,27 or multiplanarreconstructions,21,28 another option would be comparison of right and leftCBCT-reformatted cephalograms, as previously performed with dry skulls. Because landmark location in three-dimensionalimages is more difficult and time-consuming, comparison between hemifacial CBCTcephalograms could be an alternative for clinical use.
Location of facial asymmetry represents an important factor influencing individualattractiveness. A comparison betweenunilateral cleft lip and palate, orthognatic Class III and Class I malocclusionindividuals regarding attractiveness was performed. Although there were no differencesin facial asymmetry between cleft and orthognathic surgery patients, the first group wasrated as significantly less attractive. This result shows that not only the amount ofasymmetry influences attractiveness, but also its location.
An accurate exam to assess morphology and facial asymmetry, leading to successfultreatment plans, including orthognathic surgery, is important. Mandibular asymmetries,such as chin deviation in Class III malocclusion patients, were examined by means ofcomputed tomography revealing that they were due to greater growth and mesialinclination of the ramus and greater maxillary vertical excess in the oppositeside. The precise location of asymmetry iscrucial to determine details of surgical treatment planning.
CONCLUSIONS
Cephalometric measurements in CBCT-derived cephalograms showed good reproducibility.
Cephalometric measurements in full face, right and left hemifacial CBCT scans, inclinically symmetrical patients, were similar.
Footnotes
» The authors report no commercial, proprietary or financial interest in the productsor companies described in this article.
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This app is only available on the App Store for iOS devices.
What’s New
- Photos are now available in the Alignment view sidebar
- There is now a reset model rotation button in the Alignment view sidebar
- In Alignment, you can now switch between real teeth, original 3D and second 3D teeth models
- Bug fixes
- There is now a reset model rotation button in the Alignment view sidebar
- In Alignment, you can now switch between real teeth, original 3D and second 3D teeth models
- Bug fixes
11 Ratings
Information
Requires iOS 12.1 or later. Compatible with iPhone 6S, iPhone 6S Plus, iPhone SE, iPhone 7, iPhone 7 Plus, iPhone 8, iPhone 8 Plus, iPhone X, iPhone XS, iPhone XS Max, iPhone XR, iPhone 11, iPhone 11 Pro, iPhone 11 Pro Max, 12.9-inch iPad Pro, 12.9-inch iPad Pro Wi-Fi + Cellular, iPad Pro (9.7‑inch), iPad Pro (9.7-inch) Wi‑Fi + Cellular, iPad (5th generation), iPad (5th generation) Wi‑Fi + Cellular, iPad Pro (12.9‑inch) (2nd generation), iPad Pro (12.9‑inch) (2nd generation) Wi‑Fi + Cellular, iPad Pro (10.5‑inch), iPad Pro (10.5-inch) Wi‑Fi + Cellular, iPad (6th generation), iPad Wi-Fi + Cellular (6th generation), iPad Pro (11-inch), iPad Pro (11-inch) Wi-Fi + Cellular, iPad Pro (12.9-inch), iPad Pro (12.9-inch) Wi‑Fi + Cellular, iPad mini (5th generation), iPad mini (5th generation) Wi-Fi + Cellular, iPad Air (3rd generation), iPad Air (3rd generation) Wi-Fi + Cellular, iPad (7th generation), iPad (7th generation) Wi-Fi + Cellular, and iPod touch (7th generation).
Supports
Family Sharing
With Family Sharing set up, up to six family members can use this app.
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