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 (PA_ceph) 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 PA_ceph, 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 PA_ceph and groups CT₁, CT₂ and CT₃, respectively, were then examined by means of a Ppaired t-test. was performed between the group PA_ceph 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 (PA_ceph), 0.036 (CT₁), 0.025 (CT₂), and 0.038 (CT₃) in ratio measurement and 0.417 (PA_ceph), 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 PA_ceph, 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 PA_ceph 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 PA_ceph. 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 PA_ceph, 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 PA_ceph. 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 PA_ceph, 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]

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	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 (PA_ceph) 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 cephalogramPA_ceph 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 cephalogramPA_ceph 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.}