University J Dent Scie 2015; 1(2) : 15-18

ABSTRACT : Aim: To assess the variations in linear parameters of left, right & combined cephalograms (CBCT) & to establish a method of quantifying skeletal asymmetries which will aid in treatment planning during orthognathic surgeries. MATERIAL AND METHODS: Pre Orthodontic anonymised CBCT scans of 32 healthy adults of age 18-28 years. The DICOM images were loaded into Dolphin 11.5,orientation of hard & soft tissue was done in a horizontal & vertical plane. The scans were then cut from the middle half in a vertical plane to make it as a right & a left half & a combination view is also taken. Two dimensional lateral cephalograms which were then loaded to Dolphin was used to Digitize for cephalometric tracings of the two dimensional images. 8 parameters were traced. RESULTS: No Statistical significant difference between the right side and the combined view (p > 0.05), also no statistical significant difference between the left side measurement and the combined measurement (p > 0.05)was present. CONCLUSION: CBCT generated lateral cephalograms computed by the dolphin software are extremely accurate & can be used for craniofacial analysis.

1 2 3 4 5Surabhi Singh, Rajesh B Dhirawani, Jayant Marya, Siddharth Singh, Anup Belludi and Priyanka Dausage1 2 3 Senior Lecturer , Department of Orthodontics and Dentofacial Orthopedics Professor and Head,

4 P.G student 2nd year, Senior Lecturer, Department of Oral and Maxillofacial Surgery,6 Senior Lecturer , Department Of Pedodontics and Preventive Dentistry Hitkarini Dental College,

5and Hospital, Jabalpur, India Professor ,Department of Orthodontics and Dentofacial Orthopedics KLE, No. 20, Yeshwanthpur, Suburb, IInd Stage, Tumkur Road, Bengaluru, Karnataka

INTRODUCTION : Digital imaging is the display of

filmless radiographs. More importantly the images are

captured in a computer & displayed almost instantly,

facilitating operative procedures that now can be image 1 guided. Before the invention of the cephalometer, knowledge

regarding the process of facial growth was based heavily on

skeletal material that was by its nature cross-sectional.

The strength of the cephalometric technique was that it

allowed the longitudinal study of changes in the growing face.

CBCT images offer new information about patients. Since its

introduction in 2001, 3D cone beam imaging has shown

logarithmic growth. The image contains information that is

simply not seen on a traditional cephalometric image. As

health care professionals, orthodontists naturally want to

improve patient care. One way to improve patient care is to 2 have better information about the patient's problem.

There is already evidence that the treatment of some

orthodontic conditions, such as supernumerary and impacted

teeth, benefit from 3D imaging. Surgical planning for patients

with jaw asymmetry e.g – Hemifacial Microsomia can benefit

from 3D imaging. This allows measurements of true

dimensions without the customary problems of

magnification, superimposition & distortion.Therefore, one

of the reasons CBCT scanning is gaining momentum in

clinical practice is the desire for excellence in patient care.3

With the CBCT, a full scan of the head can be performed, in a

few seconds during which the patient receives an effective

dose of only about 50 µSv, which equals the total dose of

conventional radiographs that are now considered essential

for almost every orthodontic patient, such as the lateral 4cephalogram & the panoramic radiographs.

MATERIAL & METHOD : 32 Pre orthodontic anonymised

CBCT scans belonging to patients available with the Imaging

Centers at Delhi (Mahajan Imaging Diagnostic Centre) &

Bombay (Insight CBCT Centre).

The raw images were exported using i-CAT Vision software

into DICOM files. The DICOM images were loaded into

Dolphin 11.5 software, then the orientation of hard tissue was

done in a horizontal plane & vertical plane( Figure 1), then the

soft tissue orientation was done over the hard tissue( Figure

2). The CBCT scan were then cut from the middle half in a

vertical plane to make it as a right half & a left half. A

combination view was also taken in which left side was

EVALUATION & ASSESSMENT OF VARIATION IN LINEAR PARAMETERS OF LEFT, RIGHT AND COMBINED CEPHALOGRAMS GENERATED BY CONE BEAM COMPUTED TOMOGRAPHY

Journal of Dental Sciences

University

Key Words : Cone Beam Tomography, Cephalogram, Dolphin software

Source of support : NilConflict of interest : None

OriginalResearch

Paper

15

superimposed on the right side.

Figure 1 : Showing Orientation Of Mid-sagittal & Axial

Planes In Hard Tissue Front

Figure 2: Showing Orienting The Soft Tissue Over The Hard

Tissue Front

Using this procedure the CBCT scan of 1 patient was made

into 3 two- dimensional lateral cephalograms which were

then loaded to Dolphin (10.5 version) was used to 'Digitize'

for cephalometric tracings of the 2D images ( Figure 3).

Following landmarks were traced on Dolphin10.5 (Figure 4):

N – Ans, Ans – Me, S – Go, Ptm – Ans, Co – Gn, Co – A, Co –

Go, Go – Me

Figure 3: Showing Derived 2d Lateral Cephalogram Using

3d Models

Figure 4: Cephalometric Tracing Done On Dolphin

RESULTS : No Statistical significant difference between the

right side and the combined view (p > 0.05), also no statistical

significant difference between the left side measurement and the

combined measurement (p > 0.05)was present.

DISCUSSION: Cone Beam Computed Tomography offers

elaborate information about the details of the patient's images

that cannot be observed on the conventional cephalogram

images. With the increasing use of Cone beam Computed

Tomography application in Orthodontic treatment planning in

certain conditions such as supernumerary teeth, impacted teeth

& more importantly in patients requiring orthognathic surgeries

specially with skeletal asymmetries, as 3D images give more

University J Dent Scie 2015; 1(2) : 15-18

16

University J Dent Scie 2015; 1(2) : 15-18

information pertaining to the left & the right sides than

compared to conventional cephalograms which give only 2D

information.

Cone beam computed tomography (CBCT) technique

presents an innovation of tomographic imaging systems and

subsequent volumetric image reconstruction for dentistry.

When compared with other methods of tomographic imaging

CBCT is characterized by rapid volumetric image acquisition 5from a single low radiation dose scan of the patient.

CBCT systems have been designed for imaging hard tissues

of the maxillofacial region. CBCT is capable of providing

sub-millimetre resolution in images of high diagnostic

quality, with short scanning times (10–70 seconds) and

radiation dosages reportedly up to 15 times lower than those 6of conventional CT scans.

In orthognathic surgeries like Bilateral Saggital Split

Osteotomy Pre surgical & post surgical CBCT scans can be

done with 3D models registered on the surface of cranial base.

They can be later on superimposed to know the location,

magnitude & direction of the mandibular displacement. This

would be helpfull in quantification of vertical, transverse &

antero-posterior ramus displacement, & it has been concluded

that CBCT allows clinically accurate & reliable 3D linear 7measurements of craniofacial complex.

Studies to determine the accuracy & reliability of 3D cranio-

facial measurements obtained from CBCT scans of a dry

human skull have been done. Inter-landmarks linear

measurements are made directly on the skull & compared

with the same measurements made on CBCT scans. When

evaluated CBCT allows clinically accurate & reliable 3D 8linear measurement of craniofacial complex.

Comparison of accuracy of craniometric measurements have

been done on lateral cephalograms & on CBCT images with

fiducial markers placed on known craniometric landmarks of

dry skull & have been evaluated using CBCT & conventional

lateral head films were taken subsequently. All measurements

were repeated within a one-month interval, and intra-class

correlations were calculated & it was observed that no

statistically significant difference was noted between CBCT

measurements & direct craniometric measurements. 2D

cephalometric norms cannot be readily used for 3D

measurements because of differences in measurement 9accuracy between the two exams.

The aim of this study was to evaluate the lateral cephalograms

data's from computer generated Cone Beam Computed

Tomography scans. Assessment of the variations in linear

parameters of left, right & combined cephalograms were done to

establish a accurate and reliable method of evaluating

cephalograms which can help orthodontists & maxillofacial

surgeons understand & quantify the extent of skeletal

discrepancy precisely & to establish a method of quantifying

skeletal asymmetries which will aid in treatment planning during

orthognathic surgeries.

Few studies have beent attempted to assess the accuracy of

cephalometric measurments as applied three dimensionally

because of known intrinsic limitations of these images, such as 10 distortion & magnification. No statistically significant

difference was found between the CBCT measurments of left,

right & the combination side, & the p value is showing that p >

0.05.

Although the statistical results are insignificant there is a high

level of reliability, accuracy & reproducibility which make it

clinically significant. The maxilllary length was measured from

Co – A & Ptm – Ans this would help us observe if there is a

unilateral discrepency. N - Ans will help us to evaluate the upper

anterior facial height in cases of vertical maxillary excess

patients. Ans – Me indicates the lower anterior facial height &

any discrepency can be accurately quantified. Previous studies

have shown that there is more skeletal discrepency & facial

asymmetries in the mandible than in the maxillla especially in

skeletal class III patients & some of these patients fall into the

category of surgical envelope of discrepency. In such cases high

reliability of unilateral landmarks are necessary. The parameters

which we have considered like Co – Gn, Co – Go & Go – Me will

show if there is any skeletal asymmetry in the mandible. The

parameter S – Go shows the posterior facial height & the

measurments on the left & right side indicate if there is any

discrepency present.

Several Studies have been done to evaluate the precision of

cephalometric landmark identification using the CBCT &

Conventional cephalometric views & have concluded that

CBCT volume images provide generally more precise

identification of traditional cephalometric landmarks. More 11precise location of the Condyle & Gonion has been observed.

In this study DICOM files were used to create 2 dimensional

radiographs on Dolphin Cephalomertic software & a method of

evaluating unilateral & bilateral landmarks was established. The

number of clinicians using 3 dimensional records during

diagnosis & treatment planning stages are increasing steadily.

The purpose of this study was to give the clinician a reliable

method of quantifying the measurements on a lateral

cephalogram using images generated from CBCT to overcome

17

University J Dent Scie 2015; 1(2) : 15-18

the drawbacks of Conventional cephalograms like projection

errors, magnification errors & limitations of 2D over 3D.

SUMMARY & CONCLUSION : In this study pre

anonymised CBCT scans of 32 patients belonging to age

group of 18 – 25 years were analysed. All the CBCT scans

were taken by i-CAT (Imaging Science International,

Germany) & the images were exported using i-CAT vision

software.

Although the statistical results are insignificant there is a high

level of reliability, accuracy & reproducibility which make it

clinically significant. The maxilllary length was measured

from Co – A & Ptm – Ans this would help us observe if there

is a unilateral discrepency. N - Ans will help us to evaluate the

upper anterior facial height in cases of vertical maxillary

excess patients. Ans – Me indicates the lower anterior facial

height & any discrepency can be accurately quantified. The

parameters which we have considered like Co – Gn, Co – Go

& Go – Me will show if there is any skeletal asymmetry in the

mandible. The parameter S – Go shows the posterior facial

height & the measurments on the left & right side indicate if

there is any discrepency present.

Lateral cephalograms are 2 dimensional & have intrinsic

limitations that result in distorted images & magnification

errors. CBCT generated lateral cephalograms computed by

the dolphin software are extremely accurate & can be used for

craniofacial analysis.

REFERENCES :

1. Allan G.Farman et al In Practice How going Digital will

affect the dental office. JADA june 2008; Vol 139; 163-

195.

2. Mark G. Hans et al Cone Beam Computed Tomography :

A link with the past, a promise for the future. Seminar in

orthodontics 2011; 17; 81-87.

3. Ashima Valiathan et al 3D CT Imaging In Orthodontics:

Adding a new dimension to diagnosis & treatment planning.

Trends biomater. Artif. Organs 2008; vol 21 (2)116-120.

4. James K. Mah et al advanced application of cone beam

computed tomography in orthodontics. Seminar in

orthodontics. 2011; 17; 57-71. .

5. C A Lascala et al Analysis of the accuracy of linear

measurements obtained by CBCT – NewTom.

Dentomaxillofacial Radiology 2004; 33; 291 – 294.

6. Mazyar Moshiri et al Accuracy of linear measurements

from imaging plate & lateral cephalometric images derived

from CBCT. AJODO 20O7; 132; 550 – 560.

7. Lucia H. S. Cevidanes et al 3 dimensional CBCT for

assessment of mandibular changes after orthognathic

surgery. AJODO 2007; 131; 44 – 50.

8. Mauricio Berco et al Accuracy & reliability of linear

cephalometric measurements from CBCT of a dry human

skull. AJODO 2009; 136; 17.e1 – 17. E9.

9. Bruno Frazao gribel et al From 2D to 3D : an algorithm to

derive normal values for 3 dimensional computerized

assessment. Angle Orthodontist 2011;81; 3 – 10.

10. Bruno Frazao gribel et al Accuracy & reliability of

craniometric measurements on lateral cephalometry & 3D

measurements on CBCT scans. Angle Orthodontist

2011;81; 26 – 35.

11. John B. Ludlow et al Precision of Cephalometric landmark

identification: CBCT vs Conventional cephalometric

views. AJODO 2009; 136; 312. e1 – 312. e10.

CORRESPONDANCE:

Dr. Priyanka Dausage

34, Nayagaon, P.O. Vidyut Nagar

Jabalpur 482008, India

E-mail : pdausage@yahoo.co.in

18