Cone Beam Computed tomography Voxel Values of

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Key words: Cone beam computed tomography, dental structures, Hounsfield units, radiographic ... than intraoral radiography, multidetector helical. CT for diagnostic ... high diagnostic quality, with short scanning times. (10–70 .... TABLE (4) Mean HU values of compact and spongy bone with p value
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Vol. 55, 1:15, April, 2009

Cone Beam Computed Tomography Voxel Values of Dental Structures

Hamdy A. Marzook *; Yousry M. Elhawary**; Abeer A. El-gindy *** and Lobna R. S. Radwan**** ABSTRACT Objective: The aim of this study was to determine the mean values of density measurements

in Hounsfield units (HU) of dental structures using cone beam computed tomography (CBCT).

Methods: HU values of enamel, dentine, and pulp were recorded in coronal, sagittal, and

axial planes in 10 cone beam tomography scans by two investigators. Two readings from five different slices were recorded using Planmeca Romexis Viewer 2.2.7.R. computer program. Data were statistically evaluated and compared with Hu values of spongy and compact bone.

Results: CBCT HU mean values of enamel, dentine, and pulp were 2050.75167, 1312.01833,

and 706.36167 HU respectively with a high statistically significant difference. Mean HU values

of maxillary spongy bone (192.15 HU) were significantly lower than mean values of the studied structures including pulp.

Conclusion: HU values vary greatly between different dental structures. More measurement

studies may be proposed to put the standards for future improvement.

Key words: Cone beam computed tomography, dental structures, Hounsfield units,

radiographic density.

INTRODUCTION CBCT is used in oral and maxillofacial (OMF) surgery and orthodontics for numerous clinical

multi-slice computerized tomography (CT)(1). Limited cone-beam CT was found to be more useful than intraoral radiography, multidetector helical

applications, particularly for its low cost, easy

CT for diagnostic imaging of horizontal tooth root

accessibility and low radiation compared with

fracture (2).

* Lecturer of Oral Surgery, Faculty of Dentistry, Mansoura University. ** Ass. Prof. of Oral Biology Dept., Faculty of Dentistry, Mansoura University *** Lecturer of Endodontics, Conservative Dentistry Dept., Faculty of Dentistry, Mansoura University. **** Lecturer of Oral Biology Dept., Faculty of Dentistry, Mansoura University

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E.D.J. Vol. 56, No. 4

The CBCT technique was considered to have better accuracy and diagnostic value than periapical films in the detection of interradicular periodontal bone defects.(3) More detailed information was obtained about dentoalveolar fractures with CBCT compared with CT and conventional radiography. (4) Cone-beam computed tomography (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 of conventional CT scans. Increasing availability of this technology provides the dental clinician with an imaging modality capable of providing a 3-dimensional representation of the maxillofacial skeleton with minimal distortion.( 5)

Hamdy A. Marzook, et al.

be needed in certain developmental disturbances such as Amelogenesis Imperfecta or odontogenic tumours. Odontogenic tumors are frequently associated with multiple dense calcifications. These calcification patterns have been extensively investigated with conventional radiography. The significance of advanced diagnostic techniques for interpretation of the calcified material in these cases can be appreciated in quantifying the density & quality of enamel and dentine.(11) Studies about the ideal level of radiopacity of

restorations have indicated that the materials should have a radiopacity similar to that of enamel so that it would not mask or hinder the detection of recurrent

caries.(12,13) Enamel is the most highly mineralized

tissue known, consisting of 96% mineral and 4% organic material and water. The inorganic content

Attention to the revolution in oral and maxillofacial imaging consequent to cone-beam computerized tomography (CBCT) and to the ethical responsibilities of dental practitioners to ensure that the full field of view (FOV) is interpreted to maximize the diagnostic yield from the CBCT image data set that is obtained had been drawn.(6,7,8) It was previously stated that CBCT is now entering the domain of general dentistry and dental specialties where higher resolution is required. It is likely that these new systems will become commonplace in dental offices and that, as a consequence, imaging laboratories will need to concentrate on procedures needing interpretation by a specialist.(9)

is a crystalline calcium phosphate hydroxy apatite,

Hounsfield units (HU) have been the accepted standard scale for measurement of CT values since the early development of medical CT scanners, and the values of X-ray tissue absorption can be measured very accurately, thus allowing the nature of the tissue to be studied.(10)

that the bone density can be expressed in Hounsfield

Radiodensity for different dental structures may

had higher values, and these differences were more

which is also found in bone, calcified cartilage, den-

tin, and cementum. Dentine is the hard tissue por-

tion of the dentin-pulp complex and forms the bulk

of the tooth. Mature dentin is, chemically by weight, approximately 70% inorganic material, 20% organic material, and 10% water.(14)

Radiographically,

the enamel of human teeth is more radiodense than

other hard dental structures (the cementum and dentin).(15)

CBCT

provides

an

effective

option

for

determination of material density expressed as Hounsfield Units.(16) Misch and Kircos(17) suggested

units (HU) using computed tomography (CT). A comparison of mean bone density between the maxilla and the mandible in Hounsfield units under

simulated placement of miniscrews by using 3D maxillofacial CT scan data showed that the mandible

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Cone Beam Computed Tomography Voxel Values

significant in the buccal side of the posterior area. (18)

CBCT density analysis for different dental

structures, however, has not been widely evaluated

or used in clinical dentistry yet. Therefore, there is a need to establish a well-defined profile for radiodensity measurements of dental structures in CBCT.

were divided equally between pulp chamber and

root canal. A total of 600 readings were recorded for each structure. Data were tabulated, statistically evaluated and compared with 600 readings for HU

values of maxillary spongy bone and mandibular basal (compact) bone ( 300 readings for each). Statistical Analysis

AIM OF THE WORK The aim of this study was to determine the mean

values of radiodensity measurements in Hounsfield

units (HU) of dental structures using cone beam computed tomography (CBCT) scans and to

compare these values with the bone mean Hu values in the same scans.

Collected data were statistically analyzed using

SAS. One-way ANOVA test was applied to compare

the mean HU values of the enamel, dentine, pulp,

and bone to test the hypothesis that there is no

statistically significant differences between these mean values. A p value < 0.05 was considered as

statistically significant.

MATERIAL AND METHODS Hu values of dental structures including enamel,

dentine, and pulp were recorded in coronal, sagittal, and axial planes in 10 cone beam tomography scans

RESULTS A total of 2400 readings were recorded from

coronal, sagittal, and axial planes of 10 CBCT scans.

(Planmeca*) by two investigators. By moving the

Mean HU values for the studied dental structures:

from five different slices were recorded using

1312.01833, and 706.36167 HU respectively. The

curser over the selected structure, two readings

enamel, dentine, and pulp were 2050.75167,

Planmeca Romexis Viewer 2.2.7.R. computer

mean HU value of bone was 816.9 HU (table 1).

from the crown and the root while pulp readings

statistically significant with a p value < 0.0001.

program** Readings for dentine were taken equally

The differences between these values were highly

Table (1) Mean HU values of enamel, dentine, pulp, and bone with p value 0.01(non significant difference) No

Studied Structure

Number of readings

Mean HU values

Standard deviation

1

Coronal dentine

300

1329.6

169.68

2

Root dentine

300

1294.4

183.58

Table (3) Mean HU values of root canal and pulp chamber with p value