Abstract

 The purpose of this study was to evaluate the reliability of cephalometric measurement[JH1] s offrom cone-beam computed tomography (CBCT)[JH2] -generated [JH3] frontal cephalograms and the suitability of theits[JH4]  possibility of the clinical use. of CBCT generated frontal cephalograms. CBCT scans and conventional frontal (posteroanterior: P-A) [JH5] cephlalograms were taken from 30 adult patients. Each patient's CBCT image was set with according to the FH plane as the horizontal plane and the midsagittal reference plane (MSR) (running perpendicular to the FH plane and[JH6]  passing through the Na and Ba points) as the vertical reference plane. The CBCT generated frontal cephalograms waswere fabricated bygenerated  using the orthogonal Raycast method (cephalogram group CT1),  andthe orthogonal maximum intensity projection[JH7]  (MIP) (CT2) methods (cephalogram group CT2), and the generator tool provided by the employed 3-dimensional (3D) imaging software (cephalogram group CT3), respectively, while the head rotationspositions were reoriented according to the reference planes. In addition, the method using the generator tool (CT3) as provided for by 3D imaging software was also used. The Ddifferences between the measurements of group group CT1, CT2, and CT3  images and those from a conventional frontal cephalogram (group group PA[JH8] ceph) were testedcompared by paired t-test (p<0.05). Group CT11 were differednt significantly in 2two measurements, group CT2 were different significantly[JH9]  in 12, measurements[JH10]  and group CT3 were different significantly in 8eight. measurements. Group CT1 were differednt significantly in only 1one measurements out of 9nine linear ratio measurements, and group CT3, were different significantlyin 2two. ones. WhenAfter the images were reoriented alongwith respect to the reference planes, determined as above[JH11]  and then[JH12] , the CBCTgenerated frontal cephalograms were producedgenerated by means of the Raycast method,. iIt was confirmed that the resultant radiographs were similar to the conventional frontal cephalograms in terms oftheir measurements. Such a result may well suggest that the frontal cephalograms produced by using thederived by 3D CBCT reorientation can be usedeffectively for theemployed in clinical purposeapplications.

 

 

Introduction

 

Analyzing process of 3In the field of orthodontics, 3-dimensional (3D) image analysis is being developed and multiplanar reformation (MPR)[JH13]  measurement is being conducted, using MPR image is being conducted in orthodontic field, but it is true thatthough the more firmly established 2-dimensional (2D) cephalometrygram is stillremains an easier approach forto diagnosis and its method for diagnosing and measuring is more precisely establishedmeasurement.1 AndMoreover, there are certain diagnostic limitations, both in positioning craniometric points on a 3D-dimensional [JH14] image. and in Cconverting a 3D-dimensional image into a 2D-dimensional[JH15]  image brings limitations in diagnosis.2 Therefore, in most of the cases, we use cone-beam computed tomography (CBCT)[JH16]  is used only in a support role, as an which is to say, additionally information of image along with theto 2D-dimensional cephalometry.gram.

In order to maximize the utility of CBCT in orthodontic practice, the dental imaging software programs have been developed whichthat produces the cephalograms based on a 3D-dimensional CBCT images.3 There had been mMany studies have compareding thesuch virtual cephalograms which was made up by using these programs[JH17]  with the original cephalograms and the their actual measurements. TheseSome of those studies have approved the accuracy and reproducibility of, for example, the virtual lateral cephalometric radiographs generated fromby CBCT.4-7 These results suggest that CBCT-generated virtual cephalograms produced from CBCT can replace the corresponding original 2D-dimensional cephalograms.

MeanwhileHowever, the studiesy related withon frontal cephalograms generated from CBCT has beenare rare.ly conducted. Van Vlijmen et al. showeddemonstrated the the significant difference between frontal radiographs obtained from cone beam CBCT scans and conventional frontal (posteroanterior: P-A) radiographs of human skulls.8 ItThey reported that there is a clinically relevant difference between angular measurements performed onobtained from conventional frontalP-A cephalometric radiographs, compared with measurementsthose onfrom frontal[JH18]  CBCT-generated cephalometric radiographs,  from CBCT scans, owing to the different positioning of patients in both devicesthe two cases. Positioning of the pPatient positioning inwithin the CBCT device appears to be an important factor[JH19]  in cases where a 2D projection of the 3D scan ishas been madedone.8 For an alternative plan, Alternatively, Hwang et al. suggested usinga device known as the Head Posture Aligner (HPA), suggested by Hwang et al., while takingcan be used with CBCT.9 But without HPA indicator we can still set up and reorient the reference planes on a 3D CBCT image can be set up and reoriented even without the HPA, because the voxels in CBCT isare isotropic, thisand so the process doesn’t not distort the image’s information. of the image[JH20] .

In the present study, without additional equipments, the CBCT-generated frontal cephalograms, which were[JH21]  were producedset according to the reference planes[JH22] , the FH plane as the horizontal plane and the midsagittal reference (MSR) plane (running perpendicular to the FH plane and[JH23]  passing through the Na and Ba points) as the vertical plane, after which they were compared with original frontal (P-A) cephalograms. And bBy using three different methods ( orthogonal Raycast, orthogonal Mmaximum intensity projection[JH24]  ([MIP)] and the generator tool that is provided by the program3D imaging software employed)), three sets of produced frontal cephalograms (groups CT1, CT2 and CT3, respectively) were madeproduced from each set of CBCT scan data. The special aim of the present study was to evaluatedetermine which method’s cephalogram was most comparable withto the original conventional radiographs (PAceph) and, therefore, the most potentially useful in clinical practice.

 

Materials and Methods

 

Materials

The subjects consisted of 30 adult patients patients (16 males, 14 females,; average age 23.6±2.7 years) obtained fromadmitted to the collection of the dPusan National University Hospital’s Department of Orthodontics. of Pusan National University Hospital. We madegenerated[JH25] , by CBCT, three different types of frontal cephalogram constructed from CBCT of the original cephalogram of each patient,.  and used the conventional and three different types of frontal cephalograms.As stated above, herein we refer to the original P-A cephalograms as group PAceph, the frontal cephalograms generated by the orthogonal Raycast method as group CT1, those generated by the orthogonal MIP method as group CT2, and those by[JH26]  the generator tool as group CT3. [JH27] [JH28] This study was reviewed and approved by the ethics committee at Pusan National University Hospital.[JH29] 

 

 We refer to the original frontal cephalogram as PA ceph and the frontal cephalogram induced by orthogonal Raycast method as CT1, the one induced by orthogonal MIP method as CT2 and the one induced by a generator tool as CT3.

 

Methods

 

(1) Taking Conventional frontalP-A cephalograms

 Conventional frontalP-A cephalgrams were taken byusing cephalometric x-ray equipment ( Planmeca PM 2002 CC Proline,; Planmeca, Helsinki, Finland ). When taking each cephalogram, the FH plane of the patients was parallel to the floor. The lLeft and right ear-rods of the fixing equipment were inserted in each ear so thatto fix [JH30] the head. could be fixed. The machineequipment was adjusted withto a tube voltage of 60-80 kVp and a tube current of 11 mA. The exposure time was 2.3 seconds withfor a fixed focus of 152.4cm.

 

(2) Taking CBCT

 CBCT was taken with the subject in an upright position withfor[JH31]  maximum intertcuspation. The FH plane of patients, once again, was parallel to the floor. The scanning settings of the CBCT machine (Pax-Zenith3D, Vatech,; Seoul, Korea) were as follows: 24 x 19 cm field of view (FOV), 50-120 kVp tube voltage, 4-10 mA tube current, 24 seconds scan time.

 

(3) ProducingCBCT-generated frontal cephalograms from CBCT

 The CBCT data was reconstructed with 3D imaginge software ( Ez3D2009, Vatech; co.,[JH32]  Seoul, Korea). Using the FH plane as the horizontal reference plane and the midsagittal reference plane (MSR) plane (perpendicular to the FH plane and[JH33]  passing through Na and Ba points) as the vertical reference plane, the 3D volume-rendering [JH34] images waswere adjustedreoriented. After 3D volume rendering images was reorientedSubsequently, 2D-dimensional frontal images were produced by the Raycast and MIP methods, and saved asin the DICOM file format and classified as groups CT1 and group CT2, respectively. And alsoAdditionally, the frontal cephalograms produced by a generator tool which is provided bythe generator tool provided with the Ez3D2009 software waswere classified as group CT3. CT3 These latter images waswere not producedgenerated by using 3D reorientation of the volume[JH35]  images. according to the reference planes[JH36] .

 (4) Comparison of measurements between CBCT-generated frontal cephalograms and conventional frontalP-A cephalograms

 The Cconventional frontalP-A cephalograms and the 3three types of CBCT-generated frontal cephalograms were digitized and measured byby thea cephalometric analysis program (V-ceph 4.0, Cyber Med Inc.,; Seoul, Korea). 17Seventeen (17) measurement points, 9nine measurement ratios and 9nine angles were used (tTable [JH37] 2).

 

3.[JH38]  Statistical analysis

 The Mmeasurement data were statistically analyzed using SPSS (ver. 15.0 for wWindows,; Chicago, IL, USA). In order to evaluate the reliability of the measured values measured from the frontal cephalograms, 10 subjects were selected randomly after 2two weeks. The same investigator measured frontal cephalograms were re-measured by the same investigator, once again andafter which then the method error was obtained by Dahlberg,s formula.*[JH39]  And tA Bland-Altman plot was drawn to verify the reliability of the repeated measurements,. Bland-Altman plot was applied. To examine tThe differences between the conventional frontalP-A cephalograms and the CBCT-generated frontal cephalograms of the same subject,between group PAceph and groups CT1, CT2 and CT3, respectively, were then examined by means of a Ppaired t-test. was performed between the group PAceph and the group CT1, CT2, CT3 respectively.

 

Results

 

 TenThe 10 subjects chosen arbitrarily chosen subjects were assessed by the same investigator on two separate occasions at least 2two weeks apart. The Dahlberg’s formula was then applied to determineresults, indicating the random errors, which were 0.032 (PAceph), 0.036 (CT1), 0.025 (CT2), and 0.038 (CT3) in ratio measurement and 0.417 (PAceph), 0.575 (CT1), 0.430 (CT2), and 0.384 (CT3) in angular measurement. The Bland-Altman plot showed there was not anyno correlation between the measurement values and the average values. Most of the values were distributed in a 95% confidence interval (Figure[JH40] ).

The results showedTable 3 lists the mean values and standard deviations fromfor groups PAceph, CT1, CT2, and CT3, ofrepresenting 30 subjects. (Table 3). As a result fromIn the paired t-test amongresults, group CT1 showed a significant statistical difference in two measurements, which is Mn./Mx. Wwidth ratio and Cg-Agr-Hr ( p < 0.05). As for group CT2, a significant statistical difference was shown in 12 measurements: of Uupper facial height ratio, Llower facial height ratio, Mx. ratio, Mn. ratio, Mn./Mx. Wwidth ratio, rramus ratio, Ui, Cg-Jl-HR, Cg-Jr-HR, Cg-Agl-HR, Cg-Agr-HR, and Cdl-Agl-Me,; and as for group CT3, there were 8eight measurements: of Mn./Mx. Wwidth ratio, rramus ratio, ANS-Me, Ui, Cg-Jr-HR, Cg-Agr-HR, Cdl-AGl-Me, and Cdr-Agr-Me showed significant statistical difference respectively[JH41]  ( p < 0.05) (Tables 4, [JH42] 5).

 

Discussion

 

There werehave been a lot ofmany studies inon the clinical use of frontal cephalograms, particularly becauseon account of its difficulties inin the difficulty of reproducingreorienting the head position and obtaining information from frontal cephalometric analysis. HoweverIndeed, infor the treatment of orthodontic patients with dentofacial deformities, it is now clear that not only lateral but also transverse cephalometric analysis but also the need of transverse analysis is emphasizedrequired[JH43] ; and thushence the expansion of the use of frontal cephalograms as well as lateral cephalogram[JH44]  has been expanded. 10,11

Recently, Aas interests in 3D-dimensional imaginge has increased, recently, CBCT, a less expensive and lower-radiation alternative to conventional CT, has been developed,. which is less expensive and lower in radiation than the conventional CT. Accordingly, analysis using CBCT is also applied in orthodontics.[JH45]  BesidesAdditionally, various attempts to generate 2D-dimensional images from 3D-dimensional ones werehave been made, which producedand several reportsit has been reported that said 3D CBCT imaginge couldhas the potential to replace the conventional 2D-dimensional imaginges.12 However, frontal cephalograms, Iin contrast to lateral cephalograms which has been approved of its(the accuracy and reproducibility of which are well established), frontal cephalogram showed significant differences between the onethose generated from CBCT and the conventional ones.6 This is becauseThese differences, specifically of image size and form, are the effects of in lateral cephalogram, the image didn’t show much of distortion [JH46] from up-and-down head rotations[JH47] , which but in frontal cephalograms, size and form of the image could becan changed an image considerably.13 Especially, CBCT taken without ear-rod head fixation[JH48] , as compared with conventional cephalograms[JH49] , is hard tocannot easily reproduce the head position, compared with the conventional cephalogram, which fact makes it essential to calibratione theof distortion from the head rotation, when generating cephalograms from CBCT, essential.

 Hwang et al. suggested that the use of Head Posture Aligner (the HPA,) during the CBCT scan in oder toboth for construct accurate virtual frontal cephalograms usingby 3D CBCT image and it couldand for improvement of the reproducibility of CT-generated frontal cephalograms. But in CBCT, it is possible to reorient the volume data according to the reference planes, and there iswith no distortion of information, during this procedure[JH50] even without the HPA.14  

Therefore, in the present study, volume data was set according to the FH plane parallel to the horizontal plane, and controlled the head rotation was controlled to makeby aligning the mid-sagittal reference MSR plane (MSR) passon the center of the skull (i.e.[JH51]  through the Na and Ba points), and thenafter which, generated the frontal cephalograms were generated and compared with the conventional frontalP-A cephalograms.

Although the conventional posteroanterior(P-A) cephalogram can be a standard for comparison, conventional P-A cephalogram also has a limitations of errors in projection error due to cephalic inclination and rotation is a limitation.15 Therefore, while taking frontal cephalograms in a conventional method[JH52] , we took it into considerationunderstanding that cephalic rotation and inclination would decrease the effect ofcompromise the analysis, and triedwe undertook to minimize its effects. We also excluded in advance the one that has these possibilities of errors after taking cephalogram. In these cephalogramsFor example, the inclination of the head can be alternatively[JH53]  be evaluated bywith reference to the angle formed by the cervical vertebrae and the mid-sadgittal reference plane (MSR).16 BesidesAlso, whilebecause an orthogonal-projection CBCT-generated cephalogram, unlike  is a a conventional and perspective-view cephalogam, and haslacks an certain enlargement ratio, since the image from CBCT doesn’t have an enlargement ratio and it is an orthogonal projection, we usedutilized the ratio and angles measurement points, ratios and angles[JH54]  for thein our comparison.14[JH55] 

 The virtual P-A cephalograms were produced by three different methods, using the orthogonal Raycast (CT1), MIP (CT2) and perspective projection [JH56] using the generator tool (CT3) as provided for by the 3D imaging software employed (CT3), respectively. The Raycast cast[JH57]  method is a way of producinggenerates an image by following rays casted from the viewpoint of the observer to the dataset. The MIP (maximum intensity projection)[JH58]  method is achieved by evaluates,ing each voxel along an imaginary projection ray from the observer’s eyes, each voxel within a particular volume of interest, and then representsing only the highest value as the display value.17 ThereforeAs such, both methods have a major limitation: the Raycast method, which hasproducing a whole voulumetric data set, hasresults in many overlapping structures, so it haswhich in turn result in much anatomical noise and has a low resolution.; On the other hand,the MIP method, losesomitting values that are[JH59]  lower than the threshold, which leads to anleads to image distortion.

As for CBCT-generated 2D-dimensional images, low resolution and heavy noise isare mentionednoted foras itstheir defects, which makes it difficult to verificationy of a specific structures in the image[JH60] problematic.7 In the present study as well, in case of the group CT1 images produced by the Raycast method, it hadshowed lower resolution than thedid the group PAceph conventional cephalogramones, and it was hard to distinguish anatomical structures were difficult to distinguish, even if we controlled the gray scale. On the other hand[JH61] , the resolution of group CT3 resolution was relatively similar to that of the conventional P-A cephalogramgroup PAceph. But asafter a result of evaluating the reliability by Dahlberg’s formula, Tthe measurement errors in ratios ofthe group CT1 ratios turned out to be low, and there was awere relativelys high only in the angular measurements. The results of the analysis inof the Bland-Altman plot also suggests that gropugroup PAceph, group CT1, group CT2 and group CT3 all havehad a relatively high reliability, becausein that the measured values arewere distributed mostly in the 95% confidence interval.(fFigure[JH62] ) Even though group CT1 had the lowest resolution, thus it didn’t not show any significant difference in its reliability.

As for group CT1, it showed a significant statistical difference only in two measurements, which makesmaking it the most comparable withto the conventional P-A cephalogramsgroup PAceph. EspeciallyNotably, in the ratio measurements, one[JH63]  measurement for group CT1, and two for group CT3 showed a significant difference. This suggests that qualitative analysis inusing CBCTgenerated frontal cephalograms generated fromwith the rRaycast method could be a usefully effective means toof evaluatinge the facial asymmetry and frontal craniofacial deformities.

 In the ratio measurements, Mn./Mx. WR showed significant low values infor all three types of CBCT-generated cephalograms produced from CBCT compared towith the conventional onetype. The frontal cephalogram produced from CBCT showed a tendency of thetoward smaller values of measured mandibular width. being measured in a smaller value. The ramus ratio showed significant statistical differences in groups CT2 and CT3. Groups CT2 and CT3 didn’t not show well enough the overlapped structures clearly enough so that we could hardlyfor us to fully recognize the position of the condyle head, and thiswhich fact seemed to beaccount for the reason for the difference. As for group CT2 (produced by MIP method), it was harddifficult to recognize the median structures including Cg and ANS[JH64] , and itwhich induced a significant difference in the vertical ratios. TheRelatively greater UFHR and lesser LFHR were recorded infor group CT2 . was recorded than the other ones[JH65]  relatively.

In the angular measurements, the ANS-Me, which showsindicates the deviation of the Menton, showed a significant difference[JH66]  only in group CT3. Since in group CT3 the head rotation was not calibrated, angle ofthe Me angle relatedrelative to the midsagittal referenceMSR plane in group CT3 was different. In order to compare the upper and lower incisors positions, we used the angular measuredment which was an the angle between the center of the incisors and the Cr-ANS (Ui-Cr-ANS and Li-Cr-ANS). As for the upper incisors, the Ui-Cr-ANS of group CT1 was similar to that of the conventional cephalogramgroup PAceph, but for groups CT2 and CT3, it showed a significant difference. As forRegarding the lower incisors (Li-Cr-ANS), all of them showed similar results. However, the angle between the mid-point of the tooth and the Cr-ANS line showed thea biggerlarger standard deviation than the mean, which implyingies its a relatively lower reliability.

As for the angles of the Cg-Jl(r)-HR, Cg-Agl(r), and Cdl(r)-Agl(r)-Me that are formed in the structures, group CT1 hadshowed no significant difference in allany of the measured values except Agr-HR. On the other handBy contrast, groups CT2 and CT3 showed significant differences in 5five, and 4four measurements, respectively. In the case of group CT2, the MIP method caused greatsevere image distortion in the overlapped strucutures, andcaused seemingly by the head position, which was not reoriented in this group but not in CT3,[JH67]  . seemed to lead this result. Therefore, whenif CBCT iswere takenperformed, ifand the patient’s head position  waswere[JH68]  inclined toward the left andor the right[JH69] , there would be an error in the CBCT-generated frontal cephalograms (CT3) of group CT3.

FromIn the results, the CBCT generated frontal cephalograms generated by the Raycast method [JH70] (group CT1) were, after the reorientation of the head along withand the reference planes, could make it possible to obtain amost similar result withto the conventional frontalA-P cephalograms. This suggests that the use of frontal cephalograms produced fromgenerated by CBCT can be significantly expanded. widely. Imaging information obatained from CBCT data, in the present study, could be easily be converted by 3D volume reorientation to 2D conventional cephalometric analysisdata. with the 3D volume reorientation. Besides, in 3D CBCT’s effective and convenient reference-plane[JH71]  reorientation and image resolution improvement of frontal cephalograms CBCT image program, if we could conduct easily reorientation along with the reference planes and improve the resolution, the use of its clinical purpose will be easily achievablehas exciting[JH72]  clinical application implications. 

 

 

 

 

 

 

References[JH73] 

1.        Grauer D, Cevidanes L S, Proffit W R 2009 Working with DICOM craniofacial images. Am J Orthod Dentofacial Orthop 136: 460-470

2.        Cevidanes L H, Styner M A, Proffit W R 2006 Image analysis and superimposition of 3-dimensional cone-beam computed tomography models. Am J Orthod Dentofacial Orthop 129: 611-618

3.        Farman A G 2005 ALARA still applies. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 100: 395-397

4.        Kumar V, Ludlow J, Soares Cevidanes L H, Mol A 2008 In vivo comparison of conventional and cone beam CT synthesized cephalograms. Angle Orthod 78: 873-879

5.        Cattaneo P M, Bloch C B, Calmar D, Hjortshøj M, Melsen B 2008 Comparison between conventional and cone-beam computed tomography–generated cephalograms. Am J Orthod Dentofacial Orthop 134: 798-802

6.        van Vlijmen O J, Bergé S J, Swennen G R, Bronkhorst E M, Katsaros C, Kuijpers-Jagtman  A M 2009 Comparison of cephalometric radiographs obtained from cone-beam computed tomography scans and conventional radiographs. J Oral Maxillofac Surg 67: 92-97

7.        Kang J Y, Lim S H, Kim K W 2007 The reliability of the cephalogram generated from cone-beam CT. Kor J Orthod 37: 391-399

8.        van Vlijmen O J, Bergé S J, Bronkhorst E M, Swennen G R, Katsaros C, Kuijpers-Jagtman  A M 2009 A comparison of frontal radiographs obtained from cone beam CT scans and conventional frontal radiographs of human skulls. Int J Oral Maxillofac Surg 38: 773-778

9.        Sun M K, Uhm G S, Cho J H, Hwang S H 2009 Use of Head Posture Aligner to improve accuracy of frontal cephalograms generated from cone-beam CT scans. Kor J Orthod 289-299

10.     Baik H S, Yu H S, Lee K J 1997 A posteroanterior cephalometric study on craniofacial proportions of Koreans with normal occlusion. Kor J Orthod 27: 643-659

11.     Kim Y J, Rhu Y K 1989 The use of posteroanterior cephalogram in orthodontics. Kor J Orthod 19: 95-108

12.     Cattaneo P M, Melsen B 2008 The use of cone-beam computed tomography in an orthodontic department in between research and daily clinic. World J Orthod 9: 269-282.

13.     Linden V D, Boersma H 1987 Diagnosis and treatment planning in dentofacial orthopedics. Quintessence. Chicago p. 336

14.     Farman A G, Scarfe W C 2006 Development of imaging selection criteria and procedures should precede cephalometric assessment with cone-beam computed tomography. Am J Orthod Dentofacial Orthop 130: 257-265

15.     Proffit W R 1991 The search for truth: Diagnosis. In surgical orthodontic treatment. Mosbt. St Louis p. 96-141

16.     Cheon O J, Suhr C H 1990 A posteroanterior roentgenocephalometric study of skeletal craniofacial asymmetric patients. Kor J Orthod 20: 615-631

17.     Scarfe W C, Farman A G 2008 What is cone-beam CT and how does it work? Dent Clin North Am 52: 707-730

18.     El-Mangoury N H, Shaheen S I, Mostafa Y A 1989 Landmark identification in computerized posteroanterior cephalometrics. Am J Orthod Dentofacial Orthop 91: 57-61

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Image-MSR II.jpg
Image.jpg

 

 

 

 

 

 

1 박영현.jpg,1 박영현.jpg 1 박영현.jpg

 

C

 

D

 

E

 
 


C

 

B

 

A

 
                                           

E

 

Fig. 1. Image acquisition from  CBCT volumetric data: A, unoriented volume; B, oriented to obtain the correct head rotation; C, CBCT-generated P-A [JH74] cephalogram by using the Raycast-cast[JH75]  method; D, CBCT-generated P-A cephalogram by using the MIP method; E, CBCT-generated P-A cephalogram by using generator tool.

 

 

Fig. 2.  Anatomic landmarks used in thispresent study.: Cg, cCrista galli; ANS, aAnterior nasal spine; LOl, lLeft latero-orbitale; LOr, rRight latero-orbitale; Jl, lLeft jugale; Jr, rRight jugale; U6l, lLeft maxillary first molar; U6r, rRight maxillary first molar; Ui, mMidpoint of upper incisor; L6l, lLeft mandibular first molar; L6r, rRight mandibular first molar,; Li, mMidpoint of lower incisor; Cdl, lLeft condyle; Cdr, rRight condyle; Agl, lLeft antegonion; Agr, rRight antegonion; Me, mMenton.

 

 

 

 

 

 

 

Table 1.  Cephalometric landmarks and reference planes

Landmark

Description

Point

 

 

Crista galli (Cr)

most superior point at its intersection with the sphenoid[JH76] 

 

Anterior nasal spine (ANS)

the tip of the anterior nasal spine

 

Latero-orbitale left (LOl)

intersecting point between the external orbital contour laterally and the oblique line on the left side

 

Latero-orbitale right (LOr)

intersecting point between the external orbital contour laterally and the oblique line on the right side

 

Jugale left (Jl)

at the jugal process, the intersection of the outline of the maxillary tuberosity and the zygomatic buttress on the left side

 

Jugale right (Jr)

at the jugal process, the intersection of the outline of the maxillary tuberosity and the zygomatic buttress on the right side.

 

Upper 6 left (U6l)

most buccal point at upper first molar crown on the left side

 

Upper 6 right (U6r)

most buccal point at upper first molar crown on the right side

 

Upper incisor (Ui)

midpoint of upper incisor

 

Lower 6 left (L6l)

most buccal point at lower first molar crown on the left side

 

Lower 6 right (L6r)

most buccal point at lower first molar crown on the right side

 

Lower incisor (Li)

midpoint of lower incisor

 

Condyle left (Cdl)

upper most point of condyle on the left side

 

Condyle right (Cdr)

upper most point of condyle on the right side

 

Antegonion left (Agl)

the antegonial notch at the lateral inferior margin of the antegonial protuberances on left side.

 

Antegonion right (Agr)

the antegonial notch at the lateral inferior margin of the antegonial protuberances on right side.

 

Menton (Me)

the most inferior point of the symphysis of the mandible

Plane

 

 

FH plane

constructed by connecting both sides of porion and right orbitale

 

Midsagittal reference

(MSR) plnane

perpendicular to FH plane and [JH77] passing through Na (Nasion)  and Ba (Basion)

 

 

 

Table 2. Measurements

Measurement

Description

Linear Measurements: ratio

 

Upper facial height ratio (UFHR)

Cg-ANS/Cg-Me

Lower facial height ratio (LFHR)

ANS-Me/Cg-Me

Maxillary height ratio (Mx.HR)

ANS-Ui/ANS-Me

Mandiblualar height ratio (Mn.HR)

Li-Me/ANS-Me

Mandible-maxillary width ratio

(Mn./Mx. WR)

Agl-Agr/Jl-Jr

U6-maxillary width ratio (U6/Mx. WR)

U6l-U6r/Jl-Jr

L6-mandiblualr width ratio (L6/Mn. WR)

L6l-L6r/Agl-Agr

Left-right ramus ratio (Ramus ratio)

Cdl-Agl/Cdr-Agr

Left-right body ratio (Body ratio)

Agl-Me/Me-Agr

Angular measurements

 

ANS-Me-MSR

Angle between line ANS-Me and MSR

Ui-Cr-ANS

Angle between Ui and line Cr-ANS

Li-Cr-ANS

Angle between Li and line Cr-ANS

Cg-Jl-HR

Angle between line Cg-Jl and line Jl perpendicular to MSR

Cg-Jr-HR

Angle between line Cg-Jl and line Jr perpendicular to MSR

Cg-Agl-HR

Angle between line Cg-Agl and line Agl perpendicular to MSR

Cg-Agr-HR

Angle between line Cg-Agr and line Agr perpendicular to MSR

Cdl-Agl-Me

Angle between line Cg-Agl and line Agl-Me

Cdr-Agr-Me

Angle between line Cg-Agr and line Agr-Me

 

 

 

 

Table 3.  Data from conventional frontalP-A cephalogram group (PAceph) and CBCT-generated P-Afrontal cephalaograms groups

Variables

PAceph

CT1

CT2

CT3

Mean± SD

Mean± SD

Mean± SD

Mean± SD

UFHR

0.44 ± 0.02

0.44 ± 0.03

0.50 ± 0.04

0.45 ± 0.03

LFHR

0.56 ± 0.02

0.56 ± 0.03

0.50 ± 0.04

0.55 ± 0.03

Mx.HR

0.44 ± 0.04

0.44 ± 0.03

0.41 ± 0.03

0.43 ± 0.03

Mn.HR

0.58 ± 0.03

0.58 ± 0.04

0.60 ± 0.03

0.57 ± 0.04

Mn./Mx. WR

26.90 ± 4.92

16.69 ± 4.50

18.52 ± 3.73

20.30 ± 4.98

U6/Mx. WR

0.88 ± 0.04

0.86 ± 0.05

0.88 ± 0.04

0.87 ± 0.04

L6/Mn. WR

0.59 ± 0.04

0.60 ± 0.04

0.59 ± 0.04

0.58 ± 0.03

Ramus ratio

0.98 ± 0.05

0.99 ± 0.06

1.00 ± 0.05

0.99 ± 0.06

Body ratio

0.99 ± 0.06

1.00 ± 0.08

0.97 ± 0.06

0.99 ± 0.06

ANS-Me-MSR

1.34 ± 2.50

1.15 ± 2.75

0.47 ± 1.86

0.36 ± 2.12

Ui-Cr-ANS

0.52 ± 1.85

0.57 ± 1.61

-0.37 ± 2.36

-0.29 ± 1.74

Li-Cr-ANS

0.19 ± 1.48

0.08 ± 1.33

-0.10 ± 1.27

0.08 ± 1.20

Cg-Jl-HR

58.52 ± 2.40

57.93 ± 2.83

64.07 ± 2.80

59.23 ± 2.59

Cg-Jr-HR

57.98 ± 2.75

59.63 ± 2.91

64.0 8± 1.99

59.39 ± 2.15

Cg-Agl-HR

63.91 ± 2.60

63.66 ± 2.16

67.14 ± 2.36

64.12 ± 2.16

Cg-Agr-HR

64.21 ± 1.91

66.50 ± 1.87

67.22 ± 1.95

64.94 ± 1.92

Cdl-Agl-Me

127.22 ± 6.05

126.59 ± 6.99

129.12 ± 6.80

130.49 ± 6.37

Cdr-Agr-Me

126.15 ± 5.72

126.78 ± 7.44

127.14 ± 6.68

127.14 ± 6.68

SD, Standard deviation

 

 

 

 

 

 

 

Table 4. Comparison of conventional frontal cephalogramPAceph group andwith CBCT-generated frontal cephalograms groups-: linear measurement

Variables

PAceph - CT1

PAceph - CT2

PAceph - CT3

Mean±SD

p-value

Mean±SD

p-value

Mean±SD

p-value

UFHR

0.00 ± 0.02

0.70

-0.07 ± 0.03

0.00**

-0.01 ± 0.03

0.18

LFHR

0.00 ± 0.02

0.84

0.07 ± 0.03

0.00**

0.01 ± 0.03

0.12

Mx.HR

0.00 ± 0.04

0.69

0.03 ± 0.04

0.00**

0.01 ± 0.04

0.34

Mn.HR

0.00 ± 0.04

0.88

-0.02 ± 0.04

0.02*

0.01 ± 0.04

0.53

Mn./Mx. WR

10.21 ± 3.73

0.00**

8.37 ± 2.34

0.00**

6.60 ± 2.07

  0.00**

U6/Mx. WR

0.02 ± 0.05

0.10

0.00 ± 0.04

0.78

0.01 ± 0.04

0.20

L6/Mn. WR

-0.01 ± 0.04

0.13

0.00 ± 0.03

0.67

0.00 ± 0.03

0.44

Ramus ratio

0.00 ± 0.04

0.68

-0.02 ± 0.04

0.05*

-0.02 ± 0.04

0.02*

Body ratio

-0.01 ± 0.06

0.67

0.02 ± 0.05

0.09

0.00 ± 0.05

1.00

SD, Standard deviation,  * : p 0.05,  ** : p 0.01   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 5. Comparison of conventional frontal cephalogramPAceph group andwith CBCT-generated PA cephalograms groups-: angular measurement

Variables

PAceph - CT1

PAceph - CT2

PAceph - CT3

Mean±SD

p-value

Mean±SD

p-value

Mean±SD

p-value

ANS-Me-MSR

0.19 ± 2.19

0.63

0.26 ± 1.88

0.50

0.98 ± 2.05

 0.01**

Ui-Cr-ANS

-0.05 ± 1.84

0.88

-0.37 ± 2.27

  0.04*

-0.29 ± 1.64

  0.01**

Li-Cr-ANS

0.08 ± 1.00

0.56

-0.10 ± 1.82

0.22

0.08 ± 1.09

0.60

Cg-Jl-HR

0.59 ± 2.96

0.29

-5.55 ± 3.24

  0.00**

-0.71 ± 2.16

0.08

Cg-Jr-HR

-1.65 ± 2.99

1.00

-6.10 ± 3.57

  0.00**

-1.41 ± 2.67

  0.01**

Cg-Agl-HR

0.25 ± 2.15

0.54

-3.23 ± 2.13

  0.00**

-0.21 ± 2.01

0.57

Cg-Agr-HR

-2.29 ± 2.23

0.00**

-3.01 ± 2.14

  0.00**

-0.73 ± 1.66

  0.02*

Cdl-Agl-Me

0.63 ± 4.42

0.44

-1.90 ± 4.49

  0.03*

-3.27 ± 3.88

  0.00**

Cdr-Agr-Me

-0.63 ± 4.00

0.40

-0.99 ± 3.65

0.15

-4.10 ± 3.76

  0.00**

SD, Standard deviation,  * : p 0.05,  ** : p 0.01   

 


 [JH1]i.e. gerund noun

 [JH2]OR: {Undo this change.}

 [JH3]OR (for here and all other instances throughout the paper):

-derived

 [JH4]i.e. measurement’s

 [JH5]**Hereafter, for consistency, I have used “P-A,” not “frontal”—but with the CBCT images, again for consistency, I have used “frontal.”—You can use “frontal” for both types if you prefer; however, there should be no uses of “P-A” after the initial use (in both the Abstract and the main body of the paper).

 [JH6]*OR (If it is the MSR plane that “passes through,” not the FH plane): {Delete.}

 

 [JH7]OR: capital M~, I~, P~

 [JH8]*I assume the lack of a hyphen here is intentional--if not, be sure to add hyphens here and passim....

 [JH9]Implicit in this syntax

 [JH10]… implicit

 [JH11]unnecessary

 [JH12]implicit in the foregoing “After”

 [JH13]OR: {Don’t identify this if “MPR” typically is used as such in the literature of your field.}

 [JH14]… just for consistency

 [JH15]… just for consistency

 [JH16]… OR: {Undo this change.}

 [JH17]Implicit in “such ~”

 [JH18]Implicit here

 [JH19]OR (probably better):

“a particularly important factor”

 [JH20]?

 [JH21]Ok but unnecessary

 [JH22]?

 [JH23]*OR (If it is the MSR plane that “passes through,” not the FH plane): {Delete.}

 

 [JH24]OR: three caps (M, I, P)

 [JH25]OR: constructed

 [JH26]… ok to omit “generated” here

 [JH27]… moved up to here from below

 [JH28]*Actually, this is somewhat repetitive (in relation to the previous paragraph)—probably it’s ok to keep this here (because the previous paragraph is the end of the Introduction), but alternatively, to avoid the repetition, you could just cut (delete) this and have a very short “Materials” paragraph (two sentences). –Your choice.

 [JH29](inserted period)

 [JH30](?) OR:

immobilize

 [JH31]*?

 [JH32]… consistency

 [JH33]*OR (If it is the MSR plane that “passes through,” not the FH plane): {Delete.}

 [JH34]*(?) OR:

rendered

 [JH35]*(?) Should this be “volume-rendering” (or “volume-rendered”)-?

 

--same question for all similar uses of “volume” throughout the document

 [JH36]implicit

 [JH37](inserted space)

 [JH38]… for consistency

 

OR: Retain “3.” here, but also number  “Materials” and “methods” “1.” And “2.,” respectively.

 [JH39]?

 [JH40]Insert figure # here.

 [JH41]implicit

 [JH42](inserted space)

 [JH43]OR: effective

 [JH44]implicit

 [JH45]implicit / already established / awkward

 [JH46]implicit

 [JH47]**(?) Here and passim, it seems that “movement(s)” would be a better (more accurate) choice of word. –If so, be sure to make the change here and everywhere else in the paper.

 [JH48]OR: immobilization

 [JH49]Better: cephalometry (if applicable)

(better parallelism)

 [JH50]implicit

 [JH51]Delete this (as implicit) if you prefer.

 [JH52]implicit

 [JH53](?) Delete this if it does not fit the context.

 [JH54]*?

 [JH55](?) not sure about this

 [JH56](?) Consistency issue: this is not mentioned in your other references to the “generator tool.”

 [JH57]… just for consistency

 [JH58]… already identified post-Abstract

 [JH59]Ok but unnecessary

 [JH60]implicit

 [JH61]ok

 [JH62]Insert # here.

 [JH63]OR:

only one”

 [JH64]OR (if there are more such structures, not just these two):

“median structures such as”

 [JH65]implicit

 [JH66]OR:

“significant differences”

 [JH67](?) OR:

{Undo this change.}

 [JH68]* “were” is correct here!

 [JH69]?

 [JH70](inserted space)

 [JH71]OR:

{Just delete as implicit.}

 [JH72]OR (if you prefer): intriguing

 [JH73]Neither included in word count nor checked

 [JH74]… just for consistency

 [JH75]… consistency

 [JH76]… just for convenient consistency

 [JH77]*OR (If it is the MSR plane that “passes through,” not the FH plane): {Undo.}