Original Research Article

Pulp volume estimation using CBCT- an in vitro pilot study on extracted

monoradicular teeth
Akshay Rathore1*, Suma GN2, Sharad Sahai3, Manisha Lakhanpal Sharma 4, Siddharth Srivastava5
1,5Senior Lecturer, 4Professor, I.T.S Centre for Dental Studies & Research, Muradnagar, Ghaziabad, Uttar Pradesh, India,
2Professor & Head, Dept. of Oral Medicine & Radiology, SGT Dental College, Vill. Budhera, Dist. Gurgaon, Haryana, India,
3Director & Consultant, Dental & Maxillofacial Diagnostics, Rajnagar, Ghaziabad, Uttar Pradesh, India

*Corresponding Author:
Email: akshaythedoc@gmail.com

Abstract
Aim: Age estimation is an important aspect of forensic odontology. Calculation of pulp volume using CBCT and its correlation
with age could be an effective, non destructive method. The aim of this pilot study was to verify and calibrate the proposed
method of calculating pulp and tooth volume using CBCT.
Materials and Method: The study was conducted on six extracted monoradicular teeth which were scanned by Cone Beam CT
(CS9300-C 3D.Carestream Health, Inc. Rochester, NY) after endodontic preparation. The tooth (TV2) and pulp volumes (PV 2)
were then calculated using imaging software (Xelis Dental software (INFINITT Inc., Seoul, South Korea). Then actual tooth
(TV1) and pulp volumes (PV1) were calculated based on the Archimedes principle. The pulp and tooth volume ratios R1 and R2
were also calculated. The estimated and actual values were compared and percentage error was calculated.
Results: The percentage error was also calculated to evaluate the accuracy which was found to be 8.84%, 2.6% and 12.7% for
TV1 and TV2, PV1 and PV2 and R1 and R2 respectively.
Conclusion: These were in accordance with the results by Yang et al.7 who obtained a percentage error of ±7.8% while the
estimated error was quite less than that reported by Star et al8 who reported the maximum percentage error to be 21% and 16%
for pulp and tooth volumes respectively.

Keywords: Age Estimation, Forensic Odontology, Cone Beam CT, Pulp Volume

Access this article online This is a continuous process and thus it can be used as a
parameter of age estimation even beyond 25 years of
Website: age. In 1995, Kvaal et al developed a new method for
www.innovativepublication.com estimating the chronological age of adults based on the
relationship between age and the pulp size on peri-
DOI: apical dental radiographs.1
10.18231/2393-9834.2016.0005 Two dimensional imaging is associated with its
inherent errors of distortion and magnification and thus
Introduction limit the accuracy. Cone-beam computed tomography
Age estimation is important in establishing identity (CBCT) is an imaging modality which generates three-
of a person and is a sub-discipline of forensic sciences. dimensional (3D) data that is accurate and at lower cost
Various medico-legal issues warrant accurate age and lower absorbed doses when compared to
estimation thus making it important in the identification conventional computed tomography (CT).
process. Multiple age estimation methods have been Yang et al.7 in 2006 estimated age through volume
reported in the forensic literature using teeth over the matching of teeth imaged by cone beam CT. The aim of
years. this study was to attempt establishing a correlation
Most methods described involve sectioning and between the chronological age of a certain individual
extraction of teeth and thus are not possible on living and the pulp/tooth volume ratio (PTV) of one of the
individuals. Radiological examination of teeth, on the teeth. The images were analyzed using the custom-
other hand, is a simple, non-destructive method used to made software and linear regression analysis was
obtain information and does not require extraction. 1,2 performed. The results of the analysis showed a
Thus techniques which are radiology dependent allow moderate correlation between the pulp/tooth volume
for age estimation in living individuals. Radiological ratio and biological age.7
studies that have been conducted mostly depend on 3D images generated by a CBCT unit allow for the
developmental stages of teeth and their correlation with calculation of volume of each tooth and corresponding
age and thus have a limited applicability only up to the pulp chamber. Thus a study was planned to estimate
age of twenty five years.3,4,5,6 age using calculation of pulp and tooth volume ratios
The dental pulp can also be used as an indicator of on mono-radicular teeth and their correlation with age.
age because it undergoes regression in size with To validate the research protocol a pilot study was
increasing age due to secondary dentine deposition.
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Akshay Rathore et al. Pulp volume estimation using CBCT

conducted on extracted teeth which verified the efficacy from the rest of tooth structure, and the segmented pulp
of the method when compared to the gold standard. was saved as a new object and rendered in a different
color (Green). Finally, the "Merge" tool was selected to
Materials and Method display the volume of the pulp (PV2).
The study was conducted in the Department of The object analysis tool in Xelis Dental software
Oral Medicine and Radiology, I.T.S Centre for Dental enabled calculation of ROI Histogram for volume
Studies and Research, Muradnagar, Ghaziabad, Uttar assessment of the pulp cavity and the tooth. Then the
Pradesh, India in collaboration with Dental and PTV ratios were calculated for each study subject.
Maxillofacial Diagnostics, Ghaziabad, Uttar Pradesh, Next the teeth were filled with impression material
India between April 2013 and May 2013. Intact and (hydrophilic polyvinyl siloxane impression material),
fully developed six mandibular extracted monoradicular Aquasil Ultra XLV (Ultra Light Body), DENTSPLY
teeth i.e. mandibular lateral incisor, mandibular canine using a Dispensing gun (3M USA). The volume of the
and mandibular first premolar were included which whole tooth was measured by the method based on
were free from any morphological abnormalities. Teeth volume displacement by Archimedes’ principle, which
with restorations, prosthetic rehabilitation, caries, was generally used in determination of density of
attrition, abrasion, erosion, periapical pathology, root various materials. The buoyant force on a submerged
resorption, developmental anomalies were not selected. object is equal to the weight of the liquid displaced by
The pulp canals of the six selected teeth were the object. The volume was calculated by, V = (m1g-
prepared endodontically. The cone-beam CT images m2g) / 1g = (m1 -m2)/1, where 1 is the density of the
were taken (CBCT Unit – CS9300-C 3D.Carestream liquid, V the submerged volume of the object, g the
Health, Inc. Rochester, NY) using the high resolution constant 9.8 N/kg, m1 the mass of the object and m2 is
dental mode at 84 kV, 5mA. Pulp and tooth volume was the apparent mass when submerged.7
calculated using the voxel counting software (Xelis Both m1 and m2 of all the teeth were measured in
Dental software (INFINITT Inc., Seoul, South Korea). the Department of Biotechnology, I.T.S-CDSR,
The total scan time was 20seconds. Study images were Muradnagar, and Ghaziabad. Electro-balance
reconstructed from the volumetric dataset, in planes (Shimadzu Analytical India Pvt. Ltd) with a glass
perpendicular to the selected tooth axes i.e. (True and beaker (50ml, Borosil, India) of absolute ethyl alcohol
oblique axial, coronal and sagittal) with a thickness of with the density of 0.78 g/cm3 was used for volume
0.09 mm and an interval of 0.09mm. Cross-sectional measurements.
images with a thickness of 0.09 mm and an interval of Each tooth was measured two times. First the
1mm were also prepared. Image assessment was actual mass, M1 was determined, next when it was
performed by specially trained Oral & Maxillofacial submerged in the alcohol, M2 was determined. Then the
radiologist for volume estimation using the CBCT tooth volume was calculated (TV1). Next the dental
software. substrate was dissolved by immersing samples in
The lines were dragged to reorient the tooth to be successively 30% Hydrochloric Acid (HCl) for 36 h
analyzed in all three axes and the file was renamed and and 2.5% Sodium Hypochlorite (NaOCl) for 10 min.
saved. After reorienting, the data were re-sliced and the The same methodology was used to determine the
file was saved in a separate folder from the source file. volume of remaining silicon core which calculated the
Next the selected tooth was segmented using the pulp volume (PV1).7
segmentation tool of the software. A mask was created Finally the pulp/tooth volume ratios were
followed by selection of optimal grayscale threshold calculated. This allowed comparing the outcome of the
which showed the tooth within the bone. The mask was software with the gold standard measures of the pulp.
then cropped in all three axes to the closest dimension The statistical analysis was done using SPSS (Statistical
of the tooth. Then the regions not belonging to the tooth Package for Social Sciences) Version 16.0 Statistical
were selected and removed manually slice by slice thus Analysis Software.
removing parts of the cortical bone and adjacent teeth.
This segmentation cannot be established by selecting Results
optimal grayscale threshold because there is a minimal Six extracted mandibular monoradicular teeth were
or no gray value difference between these closely analyzed and their actual tooth (TV1) and pulp volume
apposed tooth anatomical structures. This segmentation (PV1) was calculated by the method based on volume
process separates the tooth structure from within the displacement by Archimedes’ principle. This allowed
bone and a final image is generated. A 3D volume comparing the gold standard measures of the tooth
calculation of this image using the "Merge" tool gives (TV2) and pulp volume (PV2) with the outcome of the
the tooth volume (TV2). software.
After this using the image segmentation, different Mean of actual tooth and pulp volume was found to
regions of interest were identified within the pulp cavity be 541.72±169.67 mm3 and 27.63±3.13 mm3
on selected sequential slices. The "Pick and Grow" tool respectively (Table 1, Table 2) and mean of the
in object tools was then used to segment the pulp cavity estimated tooth and pulp volume by CBCT was found
J Dent Specialities.2016;4(2):124-130 125
Akshay Rathore et al. Pulp volume estimation using CBCT

to be 493.80±169.68 mm3 and 28.35±4.49 mm3 (Table statistically significant [p=0.486].The difference in
1, 2) while the mean for PTV Ratios R1 and R2 was PTV Ratios R1 and R2 was statistically significant
found to be 0.0550± 0.0168 and 0.0620±0.017 [p=0.002].
respectively (Table 3). The percentage error was also calculated to
The difference in the actual and estimated tooth evaluate the accuracy which was found to be 8.84%,
volume was statistically significant [p=0.002] while the 2.6% and 12.7% for TV1 and TV2, PV1 and PV2 and
difference in actual and estimated pulp volume was not R1 and R2 respectively. (Table 4)

Table 1: Table showing mean actual and estimated tooth volumes for all 6 teeth in mm3
Tooth Volume Mean S.D. P-value
TV1 541.72 169.67 0.002
TV2 493.80 169.68

Table 2: Table showing mean actual and estimated pulp volumes for all 6 teeth in mm3
Pulp Volume Mean S.D. P-value
PV1 27.63 3.13 0.486
PV2 28.35 4.49

Table 3: Mean PTV ratios for all 6 teeth

Ratio Mean S.D. P-value
R1 (PV1/TV1) 0.0550 0.0168 0.002
R2 (PV2/TV2) 0.0620 0.017

Table 4: Percentage error for all 6 teeth

Mean S.D. % Error
TV1-TV2 47.92 18.68 8.84%
PV1-PV2 0.72 2.35 2.6%
R1-R2 0.007 0.0028 12.7%

Fig. 1a: Endodontically prepared extracted tooth

J Dent Specialities.2016;4(2):124-130 126

Akshay Rathore et al. Pulp volume estimation using CBCT

Fig. 1b: Radiograph of endodontically prepared extracted tooth

Fig. 2: Dispensing gun (3M) with polyvinyl siloxane Cartridge

Fig. 3: Electric balance, Shimadzu, Japan

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Akshay Rathore et al. Pulp volume estimation using CBCT

Fig. 4: Segmentation process showing the pulp volume marked with different color

Fig. 5: The object analysis tool in Xelis Dental s/w enabled calculation of ROI Histogram for volume
assessment of the pulp cavity

J Dent Specialities.2016;4(2):124-130 128

Akshay Rathore et al. Pulp volume estimation using CBCT

8.84%, 2.6% and 12.7% for TV1 and TV2, PV1 and
PV2 and R1 and R2 respectively.
These were in accordance with the results by Yang
et al7 who obtained a percentage error of ±7.8% while
the estimated error was quite less than that reported by
Star et al8 who reported the maximum percentage error
to be 21% and 16% for pulp and tooth volumes
respectively.
The total procedure including scanning, image
reconstruction, pre-processing and measurements took
about 1 hour which is much faster than the 5 h per tooth
processing time reported in a previous study on Micro
CT.9
The segmentation process could be challenging
because of its dependence on grey scale values and its
dependence on inherent resolution of Cone Beam CT.
Recent generations of cone-beam CT are available with
Fig. 6a: Tooth decalcification in 30% HCl better contrast resolution and detail which thus will
enable improved visualization of the tooth
segmentations. The technique needs to be evaluated on
living individuals and could be a very objective and
non- invasive method of estimating age.

Conclusion
Cone-beam CT scanning provides us a new method
to acquire the 3D images of teeth in living individuals
by which pulp/tooth volume can be calculated and
correlated to age. The presented method shows
promising results for age estimation in forensic
odontology.

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