EndoCal 10 Obturation Voids in Root Canal and Isthmus of a

Human Premolar:

A Synchrotron micro-CT Imaging Study

Assem Hedayat

and Pengyu Wu

College of Dentistry, University of Saskatchewan, 105 Wiggins Rd., Saskatoon, Canada

Department of Physics and Engineering Physics, University of Saskatchewan, 116 Science Place, Saskatoon, Canada

Keywords: Apex, Isthmus, Synchrotron-Radiation-based X-ray, micro-CT, Endodontic Therapy, Root Canal, EndoCal

10.

Abstract: The objective of this research is to detect and characterize voids in an Endocal 10 obturated human premolar

using synchrotron-radiation-based micro-computed tomography (SRµCT) and 3D visualization. Also, the aim

is to investigate the extent of voids present in a fine structure such as an isthmus following obturation. We

scanned an extracted human premolar that was obturated with EndoCal 10 using the Bio-Medical Imaging

and Therapy (BMIT) 05ID-2 beamline at the Canadian Light Source. We applied the non-destructive

monochromatic X-ray beam at 47 keV, and compiled 4.3 µm pixel size images utilizing a AA-40

(HAMAMATSU) beam monitor synchronized with a (HAMAMATSU C9300-124) charge-coupled camera.

We used Fiji for reconstructing the images and Avizo 9.0 for 3D rendering. The results showed voids in

different parts of the obturation as well as a partially obturated isthmus. Miicro-CT and 3D visualization show

that voids exist in the pulp chamber, root canal, and isthmus following obturation with EndoCal 10 during

endodontic therapy. We categorized the isthmus as a type V one. The study also highlights the reasons

contributing to the difficulty of obturating the isthmus. The variation in isthmus’ diameter, its irregular

branching, the presence of pulp tissue, as well as its angular orientation with respect to the root canals are

some of the reasons that impede the flow of EndoCal 10 through it.

1 INTRODUCTION

EndoCal 10 is a calcium oxide based material used in

endodontic therapy. In order to obturate a root canal,

a blend of calcium oxide, zinc oxide, and an excipient

is mixed with water and ethylene glycol and applied

(ALBUCA©, 2007). The reactions taking place lead

to the expansion of the EndoCal as it cures (Guigand

et al. 1997, Goldberg et al. 2004). Studies concluded

that EndoCal 10 is an effective sealant in endodontic

therapy (Goldberg et al. 2004, Ghaziani and Sadeghi

2008).

The criterion to evaluate the obturation totality of

a material during endodontic treatment is the

adequacy of filling root canals. It was concluded from

a micro-CT study that different obturating materials

exhibited a certain degree of voids present. These

inadequacies in obturation occurred at a significantly

higher degree in the apical region of the teeth (Wolf et

al. 2014).

In general, root canal isthmuses are prevalent in

human teeth and are classified into different types

(Hsu and Kim 1998). The presence of tissue remnants

and the associated microorganisms in these isthmuses

may affect the success of endodontic therapy. It is

indispensable to seal off isthmuses during endodontic

treatment (Von Arx, 2005). The use of micro-CT to

characterize the obturation of Isthmuses showed

partial filling that may have been caused by debris

from hard tissue and remnants of pulp tissue (Oh et.

Al. 2016).

There are no micro-CT studies that were pursued

to delineate the obturation characteristics of EndoCal

10 inside the tooth structure where it is applied.

Examples of these structures are root canal apices and

isthmuses. The objective of this research is to

delineate the degree of adequacy of Endocal 10 as an

obturating material during endodontic therapy using

the micro-CT capability of the Bio-Medical Imaging

and Therapy (BMIT) 05ID-2 beamline at the

Canadian Light Source, and to characterize the voids

present in an isthmus and a root canal.

This is a pilot study based on a case where the

extracted human premolar was obturated with

Hedayat, A. and Wu, P.

EndoCal 10 Obturation Voids in Root Canal and Isthmus of a Human Premolar: A Synchrotron micro-CT Imaging Study.

DOI: 10.5220/0006582900430049

In Proceedings of the 11th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2018) - Volume 2: BIOIMAGING, pages 43-49

ISBN: 978-989-758-278-3

EndoCal 10. Accordingly, we did not pursue a

comparison with more teeth and other materials used

in endodontic treatment.

2 METHODS

2.1 Premolar Endodontic Therapy

The two-rooted extracted human premolar used in

this study was amongst 12 other teeth selected from

the tooth bank (College of Dentistry, University of

Saskatchewan) and screened for having intact roots as

examined by a conventional X-ray machine

(Carestream CS2200, Carestream Health Inc.,

Vaughan, Canada). We stored the premolar in

Carolina solution (Carolina Biological Supply

Company, Burlington, NC, USA) at all times. We

summarize the endodontic therapy that was pursued

as follows:

1. We used a high-speed driven endodontic

diamond bur to penetrate the pulp chamber.

2. We utilized a sequence of stainless steel Kerr

Dental K-Flex endo hand files sizes 10, 15, 20,

and 25 Kerr, Orange, CA, USA) to widen the root

canals.

3. Irrigation with 5.25% sodium hypochlorite was

necessary after applying every file.

4. The crown-down technique was then carried out

employing SybronEndo K3 Engine Files (K

Dental Inc., Markham, ON, Canada) lubricated

with Glyde File-Prep RC Conditionar (Patterson

Dental, St. Paul, MN, USA). Irrigation and

drying were always carried out after every file.

5. We then applied EndoCal 10 (ALBUCA,

Montreal, QC, Canada) using a Lentulo spiral to

obturate the premolar.

6. Finally, we etched the inner walls of the premolar

above the obturation with 37% phosphoric acid,

rinsed it, dried it, covered it with 3M Scotchbond

Universal Adhesive (3M ESPE, St. Paul, MN,

USA), and restored it with 3M Filtek Supreme

composite (3M ESPE, St. Paul, MN, USA).

2.2 Synchrotron Scanning

We scanned the premolar using the Bio-Medical

Imaging and Therapy (BMIT) 05ID-2 beamline at the

Canadian Light Source (CLS). We followed the same

procedure detailed in one of our previous studies

(Hedayat et al. 2016). In this work, we subjected the

premolar to the non-destructive monochromatic X-

ray beam at 47 keV, and compiled 4.3 µm pixel size

images utilizing a AA-40 (HAMAMATSU) beam

monitor synchronized with a (HAMAMATSU

C9300-124) charge-coupled camera.

2.3 Image Reconstruction and 3D

Rendering

We used Fiji for reconstructing the images and Avizo

9.0 (FEI, Hillsboro, OR, USA) for 3D rendering. We

have used Avizo 9.0 in a previous study (Hedayat et

al. 2016), and found it a powerful tool for analyzing

micro-CT acquired data.

3 RESULTS

We used Avizo 9.0 for 3D visualization of the

premolar, and observed three distinct features in the

images: a vertical fracture along the side of one of

the roots, voids within the obturated pulp chamber

and apex of the nonfractured root, and partial

obturation within the isthmus between the two root

canals. Since we have already prepared a manuscript

identifying and analyzing the cause of the vertical

fracture along one side of one of the roots, the latter

two observations are addressed in this manuscript.

3.1 Voids in EndoCal 10 Obturated

Structures

It is clear from Figure 1(a) and (b) that one root

fractured while the other one exhibited obturation

voids at its apex. Arrow A points toward the void

while arrow B points to the fractured root.

Figure 1(a): Two roots of the premolar, one exhibiting a

crack while the other showing obturation inadequacy at its

apex.

BIOIMAGING 2018 - 5th International Conference on Bioimaging

Figure 1(b): Two roots of the premolar, one exhibiting a

crack while the other showing voids within the obturation

at its apex.

The voids in EndoCal 10 were not limited to the

apex of the root, but were also present in areas within

the obturated pulp chamber as shown in Figure 2(a).

The arrow “V” points to the void within the axial

section, as well as on the gray value profile plot in

Figure 2(b).

Figure 2(a): Axial section of the pulp chamber showing

void “V”.

Figure 2(b): Gray value profile plot reflecting the features

along the line in Figure 2(a) and especially void “V”.

3.2 Partial Obturation of Isthmus

We used Avizo 9.0 for 3D rendering of an isthmus

within the premolar. The arrow in Figure 3 points to

the isthmus which extends between the two root

canals. We were interested to learn about the extent

of EndoCal obturation through the isthmus, and

accordingly compiled a series images of sagittal and

axial sections of the area surrounding it.

Figure 3: Isthmus between the two root canals of the

premolar.

Figure 4(a) to 4(g) is a series of images of sagittal

sections illustrating the extension of the isthmus

between the two root canals. The arrows in all images

point to the isthmus. All images showed the EndoCal

as it partially obturated the isthmus from the left side.

It is significant to mention that some of the sagittal

and axial sections showed the presence of tissue

within the isthmus. For example, in Figure 4(e), while

arrows “A” and “B” point to the isthmus structure,

arrow “C” points to the tissue inside the isthmus. The

EndoCal 10 Obturation Voids in Root Canal and Isthmus of a Human Premolar: A Synchrotron micro-CT Imaging Study

appearance of the Endocal tissue inside the isthmus is

different and clearly distinguishable from that of

EndoCal 10.

Figure 4 (a) to (g): Series of Sagittal sections showing

partial obturation of the ishmus by EndoCal 10.

The axial section in Figure 5(a) illustrates the

partial obturation of the isthmus at one end with

EndoCal 10. The profile plot of gray value in Figure

5(b) shows the presence of EndoCal 10 at the peak

“B”. In contrast, the axial sections in Figures 6(a) and

7(a) shows the absence of EndoCal 10 at point “B”,

which is also reflected in the profile plots of the gray

value in Figures 6(b) and 7(b).

BIOIMAGING 2018 - 5th International Conference on Bioimaging

Figure 5(a): Axial section showing EndoCal 10 partially

obturating the isthmus.

Figure 5(b): Profile plot of gray value reflecting the features

along the line in 5(a).

Figure 6(a): Axial section showing the isthmus.

Figure 6(b): Profile plot of gray value reflecting the features

along the line in 6(a).

EndoCal 10 Obturation Voids in Root Canal and Isthmus of a Human Premolar: A Synchrotron micro-CT Imaging Study

Figure 7(a): Axial section showing the isthmus.

Figure 7(b): Profile plot of Gray value reflecting the

features along the line in 7(a).

4 DISCUSSION

Through synchrotron-radiation-based micro-

computed tomography (SRµCT) and 3D rendering,

we achieved the objective of delineating voids in an

extracted human premolar obturated with EndoCal

10. Using this non-destructive technique, we also

accomplished the aim of studying the degree of void

prevelance in an isthmus post obturation with

Endocal 10.

The high degree of fluidity of EndoCal 10 during

thorough mixing of its powder and liquid components

clearly suggests that the material has the capability to

flow throughout the prepared structures and obturate

them adequately during endodontic therapy.

Although this was observed in crevices and cracks

through 3D visualization at high resolution, there

were voids in the obturation in some areas of the pulp

chamber and apex of one root. Figure 1(b) and 2(a)

show the voids present in the pulp chamber and root

apex, respectively. This supports what was reported

earlier (Wolf et al. 2014) that obturating materials

exhibit some degree of voids present. In this case, the

voids may be attributed to the entrapment of air

bubbles during the obturation process. This also

signifies that although Endocal 10 expands following

its mixing and activation, the expansion does not

engulf and fill the gaps completely.

Visualizing the isthmus between the root canals at

a high resolution and in 3D, as shown in Figure 3, we

concluded the following:

1. The isthmus is a continuous one connecting both

root canals, and accordingly can be classified as

a type V isthmus as defined in the literature (Hsu

& Kim 1998).

2. Some 2D and 3D images showed remnants of

pulp tissue inside the isthmus.

3. The isthmus was partially obturated and Endocal

10 was able to flow to a certain extent from one

end as shown in the series of images in Figure 4.

This is an indication that no hard debris resulting

from the preparation of the root canals plugged

the isthmus.

4. Through 3D visualization, we observed that the

geometry of the isthmus is tubular in structure. It

is narrow at the root canal connecting ends and

has dead-end branches emerging from it. The

isthmus’ diameter increases to a maximum in

between its two ends, which causes a pressure

drop in the Endocal’s flow through it. The

pressure drop is an impeding factor to the flow of

Endocal 10 through the isthmus.

5. As shown in Figures 3 and 4g, the isthmus is

slanted downwards from the left root canal to the

right one. Accordingly, it was easier for the

EndoCal to flow downwards and partially

obturate the isthmus at the left end, rather than

flow upwards at the right end.

This is a single case pilot study that we plan

to expand on in the future. We plan to pursue a

comparative study that includes several teeth

obturated with Endocal 10. We also plan to study the

obturation inadequacies in teeth using other materials

BIOIMAGING 2018 - 5th International Conference on Bioimaging

during endodontic treatment. We will apply the same

techniques in data acquisition and processing as we

did in this study.

5 CONCLUSIONS

1. Similar to other obturating materials used in

endodontic therapy, voids may appear in parts of

the pulp chamber, apical region of the root canal,

and isthmus following the application of

EndoCal 10.

2. As illustrated through 3D rendering, the root

canal isthmus in this study is characterized by a

non-uniform diameter, branches, and tissue

within it.

3. With conventional endodontic therapy, it is not

possible to completely obturate an isthmus with

a structure similar to the one visualized in this

study. This is attributed to its varying diameter,

its branching architecture, and the tissue

remaining in it.

4. Through 3D visualization of the isthmus between

the two root canals in this study, we categorize

this isthmus as a type V.

6 FUTURE WORK

1. Future work, that will be comparative in nature,

is planned to apply the imaging technology and

3D rendering technique we followed in this study

to more cases of teeth obturation with Endocal 10

during endodontic therapy. The research will

delineate the voids in the obturated roots, and

evaluate the degree of obturation in the isthmuses

that might be present in those teeth.

2. It will be of value to pursue the study on other

obturating materials used in endodontic

treatment. The results will be also compared.

3. We can quantify the volume of voids and

compare the data acquired from different teeth

and using other obturating materials in future

studies.

ACKNOWLEDGEMENTS

Research described in this paper was performed at the

BMIT facility at the Canadian Light Source, which is

supported by the Canada Foundation for Innovation,

Natural Sciences and Engineering Research Council

of Canada, the University of Saskatchewan, the

Government of Saskatchewan, Western Economic

Diversification Canada, the National Research

Council Canada, and the Canadian Institutes of

Health Research.

We thank Dr. Ning Zhu for his guidance and

assistance throughout our research at (BMIT) 05ID-2

beamline at the Canadian Light Source.

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EndoCal 10 Obturation Voids in Root Canal and Isthmus of a Human Premolar: A Synchrotron micro-CT Imaging Study