Magnetic Resonance Imaging in Endodontics: A Literature Review and Clinical Considerations

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Nikita Tommy

Fifth year, Group 12

Magnetic Resonance Imaging in Endodontics: A

Literature Review and Clinical Considerations

Master Thesis

Supervisor:

Dr Jelena Gudač

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FINAL MASTER’S THESIS IS CONDUCTED

AT THE DEPARTMENT OF ORTHODONTICS

STATEMENT OF THESIS ORIGINALITY

I confirm that the submitted Final Master’s Thesis: “Magnetic Resonance Imaging in Endodontics: A literature review and clinical considerations”

1. Is done by myself.

2. Has not been used at another university in Lithuania or abroad.

3. I did not used any additional sources that are not listed in the Thesis, and I provide a complete list of references.

I confirm by e-mail, and the work will be signed after the end of the quarantine and emergency situation due to the COVID-19 pandemic in the republic of Lithuania.

30-04-2020 Nikita Tommy

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CONCLUSION OF FINAL MASTER’S THESIS ACADEMIC SUPERVISOR

ON THE DEFENSE OF THE THESIS

00-00-2020 Jelena Gudac

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FINAL MASTER’S THESIS IS APPROVED AT THE DEPARTMENT

Department of Dental and Oral Pathology

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Final Master’s Thesis reviewer

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Evaluation of Final Master‘s Thesis Defense Board:

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LITHUANIAN UNIVERSITY OF HEALTH SCIENCES MEDICAL ACADEMY

FACULTY OF ODONTOLOGY CLINIC OF DENTAL AND ORAL PATHOLOGY

Magnetic Resonance Imaging in Endodontics: A Literature review and Clinical Considerations

Master Thesis

The thesis was done

by student ……… Supervisor………

(Signature) (signature)

………. asist. Jelena Gudac

(name, surname, year, group) (degree, name, surname)

30-04-2020 30-04-2020

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EVALUATION TABLE OF THE MASTER’S THESIS

Evaluation: ...

Reviewer: ...

(scientific degree. name and surname)

Reviewing date: ... No.

MT parts MT evaluation aspects Compliance with MT requirements and

evaluation

Yes Partially No

1 _Summary

(0.5 point)

Is summary informative and in compliance with the

thesis content and requirements? 0.3 0.1 0

2 Are keywords in compliance with the thesis essence? 0.2 0.1 0

3 Introduc-

tion, aim and tasks (1 point)

Are the novelty, relevance and significance of the

work justified in the introduction of the thesis? 0.4 0.2 0 4 Are the problem, hypothesis, aim and tasks formed _{clearly and properly?} 0.4 0.2 0

5 Are the aim and tasks interrelated? 0.2 0.1 0

6 Selection criteria of the studies, search methods and strategy (3.4 points)

Is the protocol of systemic review present? 0.6 0.3 0

7

Were the eligibility criteria of articles for the selected protocol determined (e.g., year, language, publication condition, etc.)

0.4 0.2 0 8

Are all the information sources (databases with dates of coverage, contact with study authors to identify additional studies) described and are the last search day indicated? 0.2 0.1 0 9

Is the electronic search strategy described in such a way that it could be repeated (year of search, the last search day; keywords and their combinations; number of found and selected articles according to the combinations of keywords)?

0.4 0.1 0

10 Is the selection process of studies (screening, eligibility, included in systemic review or, if

applicable, included in the meta-analysis) described?

0.4 0.2 0

11

Is the data extraction method from the articles (types of investigations, participants, interventions,

analysed factors, indexes) described?

0.4 0.2 0 12

Are all the variables (for which data were sought and any assumptions and simplifications made) listed and defined? 0.4 0.2 0 13 Are the methods, which were used to evaluate the _{risk of bias of individual studies and how this} 0.2 0.1 0

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Was meta-analysis applied? Are the selected 32 statistical methods indicated? Are the results +2 +1 0

Information is to be used in data synthesis,

described?

14 Were the principal summary measures (risk ratio, _{difference in means) stated?} 0.4 0.2 0 15 Systemiza- tion and analysis of data (2.2 points)

Is the number of studies screened: included upon assessment for eligibility and excluded upon giving the reasons in each stage of exclusion presented?

0.6 0.3 0 16 Are the characteristics of studies presented in the

included articles, according to which the data were extracted (e.g., study size, follow-up period, type of respondents) presented? 0.6 0.3 0

17 Are the evaluations of beneficial or harmful outcomes for each study presented? (a) simple summary data for each intervention group; b) effect estimates and confidence intervals)

0.4 0.2 0 18

Are the extracted and systemized data from studies presented in the tables according to individual tasks? 0.6 0.3 0 19 Discussion (1.4 points)

Are the main findings summarized and is their

relevance indicated? 0.4 0.2 0

20 Are the limitations of the performed systemic _{review discussed?} 0.4 0.2 0 21 Does author present the interpretation of the _results? 0.4 0.2 0

22 _Conclusions

(0.5 points)

Do the conclusions reflect the topic, aim and tasks

of the Master’s thesis? 0.2 0.1 0

23 Are the conclusions based on the analysed material? 0.2 0.1 0

24 Are the conclusions clear and laconic? 0.1 0.1 0

25

References (1 point)

Is the references list formed according to the

requirements? 0.4 0.2 0

26

Are the links of the references to the text correct? Are the literature sources cited correctly and precisely? 0.2 0.1 0 27 Is the scientific level of references suitable for _{Master’s thesis?} 0.2 0.1 0

28 Do the cited sources not older than 10 years old form at least 70% of sources, and the not older than 5 years – at least 40%?

0.2 0.1 0

Additional sections, which may increase the collected number of points

29 Annexes Do the presented annexes help to understand the _{analysed topic?} +0.2 +0.1 0

30

Practical recommen- dations

Are the practical recommendations suggested and are they related to the received results?

+0.4 +0.2 0 31

Were additional methods of data analysis and their results used and described (sensitivity analyses, meta-regression)? +1 +0.5 0

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of each meta-analysis presented?

General requirements, non-compliance with which reduce the number of points

Is the thesis volume sufficient 15-20 <15

33 pages (-2 pages (-5

(excluding annexes)?

points) points)

34 Is the thesis volume increased -2 -1 point

artificially? points

35 Does the thesis structure satisfy the -1 point -2 points requirements of Master’s thesis?

Is the thesis written in correct

36 language, scientifically, logically -0.5 point -1 points

and laconically?

37 Are there any grammatical, style or -2 -1 points computer literacy-related mistakes? points

Is text consistent, integral, and are _-0.5 38 the volumes of its structural parts -0.2 point

General balanced? points

require-

>20%

39 ments Amount of plagiarism in the thesis.

(not evaluated)

Is the content (names of sections

40 and sub-sections and enumeration -0.2 point -0.5

of pages) in compliance with the points

thesis structure and aims?

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*In total (maximum 10 points):

*Remark: the amount of collected points may exceed 10 points. Reviewer’s comments:

Reviewer’s name and surname Reviewer’s signature  Are the names of the thesis parts in

compliance with the text? Are the

-0.5 titles of sections and sub-sections -0.2 point

points distinguished logically and

correctly?

Are there explanations of the key

-0.2 point

-0.5

terms and abbreviations (if needed)? points

Is the quality of the thesis

-0.5 typography (quality of printing, -0.2 point

points visual aids, binding) good?

41

42

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ABSTRACT

Objectives: To review the current literature on the applications, limitations, and, clinical

recommendations for the use of Magnetic Resonance Imaging in endodontics.

Search Methods and Strategy: A literature search was performed in Medline (Pub Med), Cochrane

Library, and Google Scholar databases from 2000 to December 2019 for studies evaluating the Magnetic Resonance Imaging (MRI) applications and limitations in the various aspects of Endodontics. The search strategy was limited in English language publications using the following terms in the search strategy: Magnetic Resonance Imaging, dentistry, endodontic diagnosis, periapical lesion, radiographic. The level of the studies was assessed by one reviewer.

Results: The search identified 9 publications that fulfilled the inclusion criteria. Two articles were

hand-searched in the International Endodontic Journal. The analysis demonstrated that MRI can provide a well-defined image of the hard tissue such as the dentin and enamel, also to recognize and display an image of the soft tissues like the pulp as well as dental pathologies. The literature revealed that advancements in MRI techniques allow the differentiation of cystic and periapical lesions. Newer MRI coils and systems of dental sequencing made the use of MRI more feasible in clinical practice.

Conclusion: This systemic review concluded that MRI could be used as an alternative or in

conjunction with conventional radiographs or CBCT in the future endodontic. The newer techniques of MRI that have a faster scanning time and advanced coil systems make it feasible for clinical use.

Key Words:

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ABBREVIATIONS

• MRI – Magnetic Resonance Imaging

• CBCT – Cone Beam Computed Tomography • ZTE – Zero Echo Time

• UTE – Ultrashort Echo Time

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1. INTRODUCTION

In endodontic, for accurate pathology diagnosis and treatment planning, appropriate imaging is needed for a full visualization [1]. In the clinical use the imaging technique is required to be fast, convenient, and as comfortable as possible for the patient while also providing high-quality detailed images of anatomical structures. The need for excellent imaging which meets all the requirements has lead to impressive advancements in the field.

Magnetic Resonance Imaging (MRI) is a nondestructive and noninvasive imaging technique that allows for visualization of the pulp and surrounding tissues for a confident diagnosis, without the risk of ionizing radiation [2]. The current use of MRI in medicine is mainly focused on the diagnosis of torn ligaments, tumors, and visualization of brains and spinal cord injuries. In dentistry, MRI is currently being used in oral surgery in the diagnosis of soft tissue lesions in the salivary glands, tumor staging, and examining the temporomandibular joint (TMJ) [3]. MRI can provide excellent imaging of tissues in great detail which can help clinicians in the diagnosis and treatment planning of periapical pathologies and determine the vitality of pulp [3]. Conventional MRI techniques have the ability to produce images only of soft tissue, pulp, and attached periodontal membrane and are often very time consuming which has meant that it is not suitable for clinical application [4]. However, the newer techniques (UTE, ZTE, and SWIFT) allow the visualization of the dental surface anatomy as well as the contrast between soft tissue and hard tissue. The newer techniques also allow a faster imaging time which means MRI has a better chance of being applied clinically.

Currently, in clinical endodontic practice, periapical radiographs are the most common and widely used imaging technique. Periapical radiographs are quick and easy to use and provide practical information on radicular tooth anatomy, nearby anatomical structures, and any presence of periapical pathologies. Conventional radiographs allow for a satisfactory two-dimensional imaging, but often give a distorted geometrical view with anatomical noise which can lead to an inaccurate diagnosis or miss diagnosis due to the angle the radiograph was taken [3]. This leads to the taking of several intraoral radiographs for correct diagnosis which increases patient discomfort and increased radiation exposure [3]. However, even after this, there is no assurance that all anatomical structures of relevance and pathologies will be in view. Due to these considerations the use of CBCT in endodontic practice has been on the rise as it gives a three-dimensional view with one sweep of the scanner, which rotates around the patient head capturing a cylindrical volume of data which allows for correct clinical diagnosis [3]. Many studies have been conducted recently and the use of CBCT in endodontic practice has been proven to have higher accuracy rates for correct diagnosis when compared to conventional radiographs. CBCT dominates conventional radiographs when assessing dental pulp anatomy, the

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12 number of root canals, and periapical changes after root therapy [5]. Despite this, CBCT has its drawbacks in that it has a higher radiation exposure than that of panoramic radiography. Patel S et al. [6] compared the effective dosages of different dental imaging and found CBCT to be around 7.3 µSv to 134.8 µSv which is higher than that of panoramic radiography which is about 6.3 µSv or periapical radiograph which is about 5 µSv [6]. CBCT radiation dose has a wide range due to the different factors such as the voxel sizes used for scanning, the field of view, and imaging detector used. CBCT is unable to produce images with the same resolution as conventional radiographs [6]. New MRI techniques (UTE, ZTE, and SWIFT) are being developed to produce similar imaging as that of CBCT with the added advantage of having no radiation exposure [5].

MRI technology performs a three-dimensional imaging which shows a cross-section of an organ with high spatial resolution due to an exceptional soft-tissue contrast. MRI is extensively used as a diagnostic tool for the imaging of soft tissues but the imaging of hard tissues remains troublesome with conventional techniques. The new MRI techniques with optimal sequences can deliver successful imaging of pulp morphology while being able to also visualize the vitality and inflammation processes of the pulp without contrast agents [5, 7]. MRI is even able to recognize teeth directly after trauma due to low signal output, the reason being due to lack of perfusion.

UTE and ZTE are able to image enamel and dentin by using an inverted image, but the time taken to acquire these images are not clinically practical. However, SWIFT has a sufficient short scan time and produces images by obtaining a hard tissue signal by radiofrequency excitation and simultaneous signal acquisition.

Assaf et al. [8] suggested that MRI be used in the follow-up appointment in trauma situations. This can prevent any unnecessary root canal treatment, where the tooth’s pulp is removed, cleaned, and sealed to prevent infection.

Newer advancements in MRI will make it possible to conduct diagnosis, treatment planning, and follow up in endodontics. This review aims to present the literature highlighting the applications and limitations of MRI in the various aspects of endodontics.

1.1 Aim

To analyze the applicability, feasibility, and clinical considerations of MRI in endodontic.

1.2 Tasks

• Determine if an MRI can be used clinically in the field of endodontics.

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2. SEARCH METHODS AND STRATEGY

Bioethics Approval Code- BEC-OF(U)-125

2.1 Focus question

The systematic review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The focus question, “Is MRI technique feasible and applicable in clinical endodontics?” was proposed by following the PICO principle.

Table 1. PICO table

Components Description

Population (P) In vitro and in vivo studies.

Intervention (I) MRI use in the diagnosis of pulp vitality and periapical

pathologies.

Comparison (C) MRI vs. conventional radiograph and CBCT in Endodontics.

Outcome (O) Evaluation of MRI in the field of Endodontics.

2.2 Types of Publications

Literature sources for this systematic review

The systematic review is based on an identification and selection of main information sources and literature studies conducted from electronic databases. A comprehensive search was restricted to English language articles.

2.3 Data Collection

Information and articles were gathered from the following electronic databases: Medline (Pub Med), Google Scholar, and Cochrane Library. Citations were read and verified. Articles related to the theme were qualified.

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2.4 Literature search and screening

To detect studies, a thorough electronic search was carried out according to PRISMA guidelines within Medline (Pub Med), Google Scholar, and Cochrane Library using different combinations of the following keywords in Table 2.

Table 2. Summary of keyword combinations.

2.5 Selection of articles

The studies were selected in several stages. The first stage included all the studies matched by keyword combinations. According to the exclusion criteria, filters were applied. Then filters were applied excluding the search based on the exclusion criteria. Duplicated articles and full-content publications that were not accessible without purchasing were excluded. The articles were further reviewed, including abstracts of articles. At the last stage, after a full-text analysis, evaluating their relevance according to selection criteria, they were included in this systematic analysis.

2.6 Inclusion and exclusion criteria

The final stage of screening involved full-text articles review and reading to certify study eligibility upon inclusion and exclusion criteria presented in Table 3.

Table 3: Inclusion and exclusion criteria Inclusion criteria

Studies in vivo Studies in vitro

Article written in the English language Articles published in the last 20 years

Exclusion criteria

Abstracts

Name of Database and last search dates

Keywords used Results

Medline (Pub Med) 05/09/2020

mri dentistry endodontics 49 Google Scholar

05/09/2020 mri dentistry endodontics periapical pulp vitality 333 Cochrane Library

12/09/2020

magnetic resonance imaging dentistry

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15 Practice guidelines

Commentaries

Figure 1. PRISMA flow diagram

Records identified through database searching (Medline (Pub med), Google Scholar, and

Cochrane Library) (n =385) Sc re eni ng In cl u d ed E li gi b il it y Id en ti fi ca ti on

Additional records identified through other sources

(n = 2)

Records after duplicates removed (n = 334)

Records screened (n = 22)

Records excluded- non-relevant title and abstract, different languages, instruments.

(n =2)

Full-text articles assessed for eligibility

(n =20) _{Full-text articles}

excluded- Practice guidelines, Different instruments and tasks

(n = 11) Studies included in

qualitative synthesis (n = 9)

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2.7Assessment Risk of Bias

The Cochrane risk of bias tool [20] was used to assess the studies included. Two studies [8,11] were

categorized as ‘Low Risk of Bias’. Four studies [4, 12, 18, 19] demonstrated “Some Concern’, and three studies [13, 16, 17] were classified as ‘High Risk of Bias’.

Table 5. Assessment Risk of Bias table.

Study Random Sequence generation Concealment of allocation Outcome blinding Missing outcom e data Reporting selective outcome data Risk of bias judgement Hovner et al. 2012[4] N N NI N N Some Concern Sinibaldi R et al. 2018[8] Y Y Y N N Low Risk of Bias Bracher et al. 2011[11] Y Y Y N N Low Risk of Bias Idiyatulli n et al. 2007[12] PN PN NI PN PN Some Concern Idiyatulli n et al. 2011[13] N N N N N High Risk of Bias Flugge et al. 2016[16] N N N N N High Risk of Bias Ploder et al. 2001[17] N N N N N High Risk of Bias Kress et al. 2004[18] N N Y N N Some Concern

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17 Juerchott et al. 2008[19] N N Y N N Some Concern

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3. RESULTS

Table 5. Summary of MRI sequences and image findings.

Authors Year Reference Resolution Sequence Subject Image

Findings Hovner et al. 2012 4 600 µm UTE,TSE, ZTE Extracted teeth+ in vivo Contrast of soft and solid

components Sinibaldi R et al. 2018 8 18 x 18 µm2 Multi _Slice Multi Echo sequence 3 patients extracted jawbone cores, ex vivo Able to distinguish new bone from calcified Bracher et al. 2011 11 392 _µm2 _{3D UTE 12 Patients} in vivo Identified carious lesions in high sensitivity Idiyatullin

et al. 2007 12 100 µm SWIFT Mandible in vivo and extracted teeth in vitro Visualise soft and hard tissue with short relaxation time Idiyatullin

et al. 2011 13 100 µm SWIFT 3 in vitro teeth and in vivo of 1 patient 3D imaging of soft and hard tissue Flugge et al. 2016 16 200 µm Fast low angle shot FLASH 1 dissected mandible Imaging 3D morphology of pulp Ploder et al. 2001 17 - TSE 23 teeth with complete and incomplete root formation Reperfusion seen by means of dMRI Kress et

al. 2004 18 100 µm TSE 211 teeth evaluate Able to pulpal perfusion in

vivo Juerchott

et al. 2018 19 - ECHO 11 patients characteristics Six identified to differentiate periapical

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19 cyst and

granuloma.

*- Not described

Overall the articles included demonstrated that MRI can show a detailed image of dental anatomy like enamel, dentin, pulp, and periodontal tissue. MRI is also able to recognise pulpal perfusion before the clinical cold test was able to do it. Dental MRI can recognise and show detailed imaging of pathologies which allow for differentiation of cysts and granulomas. Microcracks and necrotic pulp tissue and decay is also observable.

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4. DISCUSSION

4.1 MRI Techniques

MRI can produce images by the reaction of hydrogen nuclei of the human body to strong magnets; hydrogen nuclei in the human body have their magnetic field and are randomly orientated. When placed in a strong magnetic field they all align with the magnetic field like the motion of a rotation axis of a rigid body like a spinning top. Next a radiofrequency coil is applied to administer a radiofrequency pulse to the patient in the magnet. This radiofrequency pulse allows for all the hydrogen nuclei that were previously aligned to the magnetic field, to realign their direction to that of the radiofrequency pulse. The radiofrequency pulse is turned on for fluctuating amounts of time to create different degrees of realignment with the radiofrequency pulse. While realigning occurs the hydrogen nuclei’s all incur various amounts of energy. This energy is recorded and collected by the radiofrequency coil before the hydrogen nuclei relax and return to the original magnet field of the MRI unit [7].

„When hydrogen nuclei “relax” back to precession in alignment with the primary magnetic field of the unit, they do so with primarily two characteristic properties: T1 and T2”.

T1 sequences are commonly known as the „anatomic“ images, in a pure T1 image the signal is high so is represented in greyscale pixel as bright. T2 signals are usually pathological or functional due to the increased water content in these types of tissues. Conventional MRI techniques are unable to visualize hard tissues because the signal from hard mineralized tissue decays faster which means the MRI is unable to detect them [3].

However, recently the new ultrashort T2 sequences (UTE and SWIFT) can image tissues with shorter T2 relaxation time and lower water content which enables a visualization of hard mineralized tissue [5, 9]. UTE is able to visualise dentin and enamel however, the time taken for acquiring these images is very long as seen in vivo and in vitro applications hence unable to apply clinically [10,11]. In contrast SWIFT has a much shorter scanning timing. Idiyatullin et al. [12] was able to take 3D images with SWIFT in 10 minutes in vitro. In vivo study, SWIFT was able to acquire an imaging resolution of 400 lms in 10 minutes with an intracoil device. The author believed that the resolution was not sufficient for clinical use but with further improvements in resolution, clinical use will be possible in the future [3, 5, 12]. SWIFT in endodontics has the potential to evaluate the pulp and root structures regeneration. SWIFT technique has the capability to establish the extent of a carious lesion while also assessing pulp tissue which can significantly help in diagnosing irreversible and reversible pulpitis [13].

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4.2 Gradient Coils

MRI in medicine allows for visualisation of all soft tissue throughout the body, this is not needed in dentistry. In dentistry, for high resolution of the images, and the field of view to be focused around the teeth, the use of gradient coils is needed [14,15]. Standard head and neck coils that are used can be very uncomfortable for the patient. The patients head is usually positioned tilted back extending the neck while also bringing the jaw as close as possible to the elements of the standard head and neck coil. Standard coils often do not have suitable openings for the mouth and exert uncomfortable pressure on the patient [14]. In addition, the standard coils are placed extra orally so the image often contains signals from tissues that are not important i.e. fat tissue of the cheek. Intraoral gradient coils give a better resolution in the images and decrease the field of view to the important structures but can be very unpleasant for the patient. This is due to the placement of the intraoral gradient coils being hindered by anatomic structures in the mouth such as the frenula and torus mandibularis [15]. Idiyatullin et al. [12] suggested a loop coil that has a similar shape to an impression tray and can be inserted into a patient’s mouth easily and sits in between the arches. Sedlacik et al. [14] designed a study to test patient comfort while using a multielement receive coil array and position system. High patient comfort was reported, there was no uncomfortable pressure or extension of the neck and positioning of the coil was easy to duplicate. Pathological conditions relating to the soft tissues were imaged clearly, there was also great visibility of the pulp chamber allowing for diagnosis on the vitality of the pulp. The newer coil designs are help implement MRI into the clinical setting as previously it would have been impractical and highly uncomfortable for the patient.

4.3 Anatomy

MRI gives the ability to obtain 3D images of the soft and hard tissues of the teeth and the root canal system. MRI provides a reconstructed image that allows a better understanding of the anatomy and the physical changes that happen during inflammation, narrowing of the root canals, and of any obstructions [15]. Fluge et al. [16] investigated the differences in reconstruction with MRI technique and CBCT. It was found that MRI was able to show a reconstructed image in more detail including structures like alveolar bone, cancellous bone, vestibule and lip, periodontium, pulp, and the inferior alveolar nerve both in vivo and ex vivo. MRI was also able to show the individual branches of the inferior alveolar nerve coming from the canal and projecting into teeth. In comparison, CBCT was not able to display the mucosa or gingiva, the inferior alveolar canal was seen due to being outlined

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22 by the surrounding bone. The pulp also, in the same way was seen because of the surrounding dentin and enamel.

When UTE technique was used it effectively showed the margins between the carious part of the tooth and the calcified parts, however, the sequencing time was 25mins for a single tooth which makes it a significant obstacle clinically [16].

Fluge et al. [16] also found that when comparing imaging produced from CBCT and MRI to histological measurements, MRI was revealed to have more accurate measurements. However, when displaying hard tissue MRI is still inferior to CBCT. MRI showed more potential in imaging of inflammation or pathology of the periodontium and bone.

Ploder et al. [17] conducted a study to find the pulpal perfusion in auto transplanted teeth with MRI. The MRI allowed for viewing of the inside of the transplanted tooth without x-ray exposure to evaluate the level of reperfusion. The results concluded that it is possible for a transplanted tooth to be vital as long as there is an intact blood supply even without re-innervation. Clinically, without the use of MRI, these teeth may have had a positive reaction to the cold test thus incorrectly showing that the pulp is nonvital.

4.4 Inflammation and Pathology

A base-level dental exam always includes a tooth vitality test. This test supplies the clinician with information about the pulpal perfusion. The stimuli like cold or electricity is applied to the tooth, if the patient is unable to feel it then the tooth is considered non-vital [7,18]. However, this method is not always accurate and in some cases a tooth may be incorrectly diagnosed as non-vital. MRI has shown to be able to visualise the neurovascular bundle and produce imaging in vivo of the dental pulp with the use of contrast agents. Kress et al. [18] found that using only T1 sequencing and contrast agent there was a significant difference between the vital and non-vital teeth. However, in this study the author does state that some of the measurements taken of vital and non-vital teeth did overlap, and further studies of clinically vital teeth that have no perfusion using MRI and histological samples need to be conducted.

Juerchott et al. [19] conducted a pilot study to evaluate whether periapical cysts can be differentiated from periapical granulomas in vivo using MRI. It had been established that granulomas and cysts cannot be separated by assessing the size on radiographs. Studies using CBCT showed good results and high sensitivity to identifying periapical lesions when compared to radiographs. However, when comparing CBCT with histological slides, CBCT was found to be only moderately accurate. Using fat-saturated T2 weighted images and non-contrast enhanced T1 weighted images Juerchott et al. [19] found that MRI showed a clear difference between periapical cysts and periapical granulomas. This

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23 has a high clinical impact on endodontist as 85% of all periapical lesions are granulomas and it can be treated with non-surgical root canal treatment. Hence, the results indicate that MRI can be a dependable non-invasive diagnostic tool in apical pathology. However, it must be taken into account that this was a pilot study and the number of cases evaluated was very small. In the future there should be more studies conducted in order to investigate the results of the pilot study.

In the future we need more reliable studies to confirm the applicability of MRI in dentistry, with low risk of bias.

5. MRI IN THE FUTURE OF ENDODONTICS AND RECOMMENDATIONS

The use of MRI in endodontics in the future could become a common investigative and diagnostic tool clinically. Traditional radiograph and CBCT are perhaps the go to imaging devices for hard tissue however, MRI is better at visualisation of the soft tissues and may become the method of choice especially in endodontics. MRI is able to visualise the remnants of pulp tissue which could be a helpful tool in the future of root canal treatment. The downside to MRI is that it is very expensive, this factor may hinder the use of MRI broadly in dentistry. MRI could also be used as a tool for 3D visualisation of the root canals using imaging analysis and, in the future, may lead to automatic 3D modelling of the inner anatomy of the root canal system using computer-aided designs. In the future MRI may assist traditional radiographs in diagnostics or replace them completely as MRI is able to differentiate periapical pathologies and assess perfusion and vitality of soft pulpal tissue [6,15]. With the newer advancements of MRI, scanning times and higher resolution of imaging MRI can be recommended to be of use as one of the main imaging techniques in dentistry.

6. CONCLUSION

In conclusion, this review of the use of MRI in endodontics suggests that it is a promising alternative imaging technique of the dental pulp and periapical pathologies. MRI’s greatest advantage is that it is a non-invasive and non-ionising method of imaging. The use of new MRI techniques like SWIFT can be recommended in the clinical situation due to short scanning time with the newer gradient coil designs which allow for patient comfort.

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Magnetic Resonance Imaging in Endodontics: A Literature Review and Clinical Considerations

Nikita Tommy