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. (10â70 .... 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