Taibah University

Journal of Taibah University Medical Sciences (2015) 10(2), 123e131

Journal of Taibah University Medical Sciences

www.sciencedirect.com

Review Article

Methodologies used in quality assessment of root canal preparation

techniques: Review of the literature

Adnan Asaad Habib, PhD *, Mazen Ibrahim Taha, MS and Elias Michel Farah, MS

Department of Conservative Dentistry, Aleppo University, Syria

Received 20 July 2014; revised 4 November 2014; accepted 8 November 2014; Available online 9 January 2015

صخلملا

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-م١٩٥٠ماعنمةقباسلاتاساردللةفثكموةلماشةعجارمءارجإ:ثحبلاقرطريياعمبقيقدتلاعمةضيرعةيبطتانايبةدعاقلالخنمتاغللالكبم٢٠١٤

لالخنمو،ةيرذجلاةينقألاريضحتمييقتلةمدختسملاصاوخلاداعبتساوءاوتحاهذهيفتمدختسايتلاريياعملاوةيثحبلاقرطلاىلعزيكرتلامتةعجارملاهذه.ةيرذجلاةانقلافيظنتولكشمييقتلتاساردلا

تزجنأيتلاتاساردلاوتالاقملانمريثكلادوجوجئاتنلاترهظأ:ثحبلاجئاتنبلغأو.حساملاينورتكلإلابوكسوركيملامادختسابعوضوملااذهلوحتاساردلانمريبكءزجو.ليكشتلاىلعةردقلاتميق)٪٧١.٩(تاساردلاامك،ةعولقملانانسألاىلعيعاعشلاليلحتللةيربخملاتاقيبطتلانعةروشنملادقعلايفيعطقملاريوصتلابليلحتلامادختسانعةروشنملاتاساردلاددعدادزأ.ريخألا

دعبثدحتيتلاةيلكشلاتاريغتلامييقتلريياعملانمددعمادختسا:تاجاتنتسالادعبةانقلاليكشتىلعتاودألاةردقمييقتنأظحولدقو،ةيرذجلاةينقألاريضحت،ةينقألافيظنتمييقتتاساردعمةنراقمتاساردلامظعمىلعذوحتسااهريضحتيعاعشلايعطقملاريوصتلاةينقتبةريخألاتاونسلايفمامتهالاةدايزظحولامك.قيقدلا

;فيظنتلاةردق;ةانقللةيزكرملاةبسن;ةانقلالقن;ةانقلاةقطنم:ةيحاتفملاتاملكلاليكشتةردق;يجنتارلابلاقلاةينقت;قيقدلايعاعشلايعطقملاريوصتلا;ريضنتلاةانقلا

* Corresponding address: Department of Conservative Dentistry,

Aleppo University, Aleppo, Syria.

E-mail: adnanhabib71@hotmail.com (A.A. Habib)

Peer review under responsibility of Taibah University.

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(http://creativecommons.org/licenses/by-nc-nd/4.0/). http://dx.doi.org/10.10

Abstract

Objectives: To review the dentistry literature regarding

methodologies and parameters used to evaluate the

quality of performance of root canal debridement tech-

niques and instruments.

Methods: An extensive literature search with pre-defined

inclusion and exclusion criteria was undertaken to iden-

tify studies that assessed root canal debridement, meth-

odologies and parameters used to assess shaping and

cleaning ability of root canal debridement and in-

struments. The relevant literature in the field of end-

odontics published from November 1950 to February

2014 was reviewed using PubMed and MEDLINE da-

tabases in all languages.

Results: A large number of studies have assessed the

quality of root canal instrumentation through the eval-

uation of cleaning ability (debris, smear layer) using

histological sections and Scanning Electron Microscopy

(SEM). The majority (71.9%) of studies evaluated the

shaping ability. A body of literature has illustrated in-

vitro applications of extracted teeth in muffle system

and radiographic analysis. Additionally, the majority of

studies have used Schneider angle technique as a random

criterion. Micro-CT analysis has been increasingly used

in the last decade.

Conclusion: Several parameters are employed in the

assessment of the post-operative shape or changes in the

root canal morphology. Shaping ability of the root canal

instrumentation techniques has been more extensively

investigated than the cleaning ability. Additional care

needs to be taken regarding entire angular changes by

combining both Schneider and Canal Access Angel

(CAA) methods and their variants. Finally, more concern

his is an open access article under the CC BY-NC-ND license

16/j.jtumed.2014.11.002

A.A. Habib et al.124

regarding micro-computed tomography technique has

been expressed.

Keywords: Canal area; Canal transportation; Centering ratio;

Debridement; Micro-CT; Muffle system

� 2015 The Authors.

Production and hosting by Elsevier Ltd on behalf of Taibah

University. This is an open access article under the CC BY-

NC-ND license (http://creativecommons.org/licenses/by-nc-

nd/4.0/).

Introduction

The goal of root canal therapy is to eliminate microor-ganisms and necrotic pulp tissue debris, and to shape the rootcanal system to facilitate irrigation and placement of medi-

caments and obturation materials.1

Successful root canal treatments depend on multiplefactors such as adequate cleaning, shaping and filling of the

root canal system. However, root canal instrumentation isone of the most essential therapeutic procedures in anytreatment since it determines the efficacy of all subsequent

procedures, in addition to the fact that it includes me-chanical debridement, creation of space for medicamentdelivery, and optimized canal geometries for adequateobturation.2

The literature is replete with studies on various aspectsof instruments performance such as: cleanliness of root ca-nals after preparation, shaping ability of instruments, and

fracture properties. Several methodologies have beendescribed to evaluate the performance of root canalinstrumentation.

When analyzing the quality of root canal instrumenta-tion created by instruments and techniques, several pa-rameters can be considered, including the cleaning and

shaping ability.

Cleaning ability of instruments and techniques

Cleaning ability of endodontic instruments and prepara-tion techniques is based on the evaluation of the percentageof debris and un-instrumented root canal walls. It was

assessed in many studies by histological sections of humanroot canals (usually curved canals in maxillary andmandibular molars).3,4

This includes histological preparation of specimens,

obtainment of serial cross-sections (mm) and assessment ofremaining pulp tissue using a morphometric approach.4

Other studies have investigated cleaning ability using the

scanning electron microscope.5,6 SEM evaluation includessplitting the specimen into two halves and preparing themost visible section for SEM examination, different

parameters evaluated; smear layer, pulpal debris, inorganicdebris, surface profile.7 The studies demonstrated that evenwith most sophisticated instruments, there might be some

area that cannot be reached, cleaned or instrumented byinstruments or techniques, suggesting that all techniques ofroot canal instrumentation are unable to completelyremove pulpal debris from irregularities such as dentin

grooves and depressions.4,7,8

Shaping ability of instruments and techniques

The aim of root canal instrumentation is to form a

continuously tapered shape with the smallest diameter at theapical foramen and the largest at the orifice to allow effec-tive irrigation and filling.1 This procedure is carried outwithout any deviations from the original trajectory, in

curved and thin canals,9 using techniques and instrumentswhich have the greatest precision and the shortest workingtime.10

The purpose of studies analyzing post-operative root ca-nal shape is to evaluate the conicity, taper and flow of theprepared root canal, and maintenance of the original canal

shape. The ability of an instrument or a technique to allowthe prepared canal to stay centered is seen as a positiveaspect. Conversely, canal transportation and preparation

errors are seen as a negative aspect.11

Canal transportation is defined according to the Glossaryof Endodontic Terms of the American Association of End-odontists as: “Removal of canal wall structure on the outside

curve in the apical half of the canal due to the tendency offiles to restore themselves to their original linear shape duringcanal preparation; may lead to ledge formation and possible

perforation”.12

Various undesirable apical preparation outcomes such asdamage to the apical foramen,13 elbow formation,14 and zip

formation and perforation,11 have been described as possibleresults of canal transportation.

Many methodologies were mentioned to assess thechanges after instrumentation of root canal; these include

silicone impressions of instrumented canals which assessflow, taper, and smoothness of the walls,15,16 superimposingradiographs before and after shaping17,18 and computer

manipulation for comparative analysis19,20 via using specialsoftware programs like AutoCad21 or Photoshop.22

One of the most popular methods of in-vitro evaluation is

the “muffle system”. Bramante et al. were the first to developthis method to evaluate changes in canal diameter.23 TheMuffle system provides a plaster block around a resin-

indexed experimental tooth. The block can be custom-machined and sectioned in various planes to allow exactrepositioning of the complete block or sectioned parts of thetooth. Simultaneous evaluation and measurement of

numerous parameters are possible such as canal area, shapedform, and centering ability. Furthermore, Data can begathered both pre- and post-operatively, and can be

compared and statistically contrasted.24

The quantification of post-instrumentation root canaldeviation can be measured by “centering ratio” method,25,26

modified formulas to calculate transportation or centeringratio26,27 or by measuring pre- and post-instrumentationdentine thickness.24,28 Alternatively, it can be directlycalculated by Pythagorean theorem.19,29

Superimposing radiographs before and after shaping,17,18

Digital subtraction radiography images, and computermanipulation19,20 are useful methods to evaluate centering

ratio. Centering ratio can be calculated using the followingformula: (X1-X2/Y), X1 represents the maximum extent ofcanal movement in one direction, X2 is movement in the

opposite direction and Y is the diameter of final canalpreparation.25

Parameters used to evaluate root canal preparation 125

Other parameters, such as root-canal diameter, workingsafety (instrument fractures, perforations, apical blockages,

loss of working length -WL-), and working time, wereconsidered when investigating the performance of root canalinstrumentation created by instruments and techniques.30e32

Many of the parameters mentioned above (canal trans-portation, centering ratio, postoperative root-canal diam-eter, loss of working length, and measurements of dentine

thickness pre- and post-instrumentation) could be assessedby a non-destructive technology such as micro-computedtomography (micro-CT).

In 1995, Nielsen et al.33 found that micro-CT accurately

reproduced internal and external tooth morphology withouttooth destruction and demonstrated surface and volumechanges after instrumentation and obturation in extracted

maxillary molars. Thus, this technology has been advocatedfor the comparison of pre- and post-instrumentation images.Micro computed tomography can render cross-sectional

(cutplane) and 3D images that are highly accurate andquantifiable.2,24,34,35

Recently, Micro computed tomography technique hasbeen used in assessing accumulated hard-tissue debris after

preparation procedures specifically in fins, isthmus, irregu-larities, and ramifications-using free software for imageprocessing and analysis.36

It is well known that when curvatures are present, end-odontic preparation becomes more difficult, and there is atendency for all preparation techniques to divert the pre-

pared canal away from the original axis.37

The morphology of a curved root canal is of greatimportance to the outcome of root canal instrumentation,

with several studies being conducted to describe thecurvature.38

In 1971, Schneider et al.39 performed pioneering work onmeasuring canal angulation. Subsequently, Weine40

developed an alternative method for determining canalangulation. A third method known as the long-axis (LA)technique was first described by Hankins et al.41 In contrast,

Kyomen et al. introduced a linear parameter described as themaximum curvature height, which differs from the angularmeasurement techniques.42 Likewise, Pruett et al.

introduced a new parameter described as the “curvatureradius” for measuring root canal curvature.43

In 2005, Gunday et al. introduced the term CAA and two

new curvature parameters pertaining to the coronal zone ofcurved root canals: the curvature starting distance (y) and thecurvature height (x). They compared the new technique withSchneider method and reported that CAA evaluates the root

canal curvature more effectively.38

The Schneider method involves first drawing a line par-allel to the long axis of the canal, in the coronal third; a

second line is then drawn from the apical foramen to inter-sect the point where the first line left the long axis of thecanal. The Schneider angle is the intersection of these lines.38

In the Weine technique, a straight line is drawn from theorifice through the coronal portion of the curve, and a secondline is drawn from the apex through the apical portion of thecurve. Weine angle is the intersection of these lines. The LA

technique involves drawing a line passing through the apicalone-third of the canal, the angle formed by the intersection ofthat line with the long axis of the tooth is known as the LA

angle (Figure 1a).38

Canal access angle (CAA) was described and comparedwith Schneider angle technique. The canal orifice (A) and apex

(B) points were connected with a line. The angle formed by theintersection between this line (AB) and one drawn parallel tothe long axis of the canal from the coronal part (AC) (used in

the Schneider method), is defined as the CAA (Figure 1b). Atthe point (C) where the parallel line described in the Schneidermethod leaves the root canal a perpendicular linewas drawn to

AB. The point that the perpendicular line intersects AB is D.CD gives the curvature height (x), and the distance from Ato point D is the curvature distance (AD/y).38

Most studies that evaluated the quality of canal prepa-

ration techniques have been conducted in-vitro. The Prepa-ration of root canals may be evaluated using extractedteeth2,4,44 or simulated root canals in resin blocks.45,46

The aim of this study is to highlight the most importantmethodologies and parameters for assessing the quality of in-struments and techniques used in root canal instrumentation.

Materials and Methods

A literature search for relevant published articles onmethodologies used in the assessment of the quality of root

canal instrumentation in the context of endodontics betweenNovember 195047 and February 201436 in all languages usingPubMed and MEDLINE database searches.

The search was performed using different keywords

(‘preparation of root canal’, ‘root canal instrumentation’,‘root canal debridement’, ‘cleaning ability of instruments andtechniques’, ‘shaping ability of instruments and techniques‘,

‘changes in root canal diameters’, ‘canal transportation‘ or‘centering ratio of root canal’).

Peer-reviewed studies of the quality of preparation and

endodontic instruments have been identified throughPubMed. Articles in which keywords do not match the subjectof the search and case reports and non-English language

studies have been excluded. After removing duplicates, theremaining papers were retrieved, and their reference listschecked to identify any other articles/textbooks relevant tothe topic, which might have provided additional information.

The data have been analyzed, and weighted averages havebeen determined for each of the following: shaping ability,root canal debridement, simulated canals and extracted teeth.

Results

The search through PubMed has shown primarily a hugenumber of articles (3855). After exclusion of duplicates, ar-

ticles in which key words do not match the subject of thesearch, case reports and non-English language studies 528published papers relevant on instrumentation of root canals

were checked.380 (71.9%) studies evaluated shaping abilityand 148 (28.1%) studies assessed cleaning ability.

- The majority of studies/492 (95.2%)/used extracted teethwhile/36 (6.8%)/studies used simulated root canals in resinblocks.

In addition to the studies that have been retrieved,there are several methodologies and parameters used

to evaluate the performance of root canal instrumentation.

Figure 1: Techniques to measure the angulation of root canals. a. Schnieder(S), canal access angle (CAA), Weine(W), and Long Axsis

(LA) angles. b. CAA variables, (x) height and (y) starting distance of the root canal curvature. c.&d. Root canal curvature can have same

(S) and different CAA.

A.A. Habib et al.126

- The methodologies used to evaluate the performance ofroot canal instrumentation in most studies are:

� For cleaning ability: histological sections, scanningelectron microscope, and micro computed tomographytechnique.

� For shaping ability: silicone impressions. Radiographs

and images and computer analysis, muffle system,

modified formulas, and micro-computed tomographytechnique and its breakthroughs.

- The parameters used to evaluate the performance of rootcanal instrumentation in most studies are:� For cleaning ability: percentage of debris (pulpal debris,inorganic debris,), un-instrumented root canal walls,

smear layer, surface profile, and apically extruded debris.

Table 1: In vitro studies evaluating the cleaning ability of instrumentation using extracted teeth.

Reference

(chronologic order)

Type of study

in-vitro, ex-vivo, clinical

Samples Methodology/parameters

Walton 19763 in-vitro extracted teeth histological sections (debris)

Moodnik et al. 19765 in-vitro extracted teeth SEM (debris)

Conningham et al. 198248 in-vitro extracted teeth histological sections (debris)

Mandel et al. 199049 in-vitro extracted teeth SEM (debris)

Myers and ontgomery 199150 in-vitro extracted teeth assessment of apically extruded debris

Hulsmann et al.199751 in-vitro extracted teeth SEM (debris)

Prati et al. 20047 in-vitro extracted teeth SEM (debris, smeer layer)

Zmener et al. 200552 in-vitro extracted teeth SEM (debris)

Liu et al. 200653 in-vitro extracted teeth SEM (debris)

De-Deus et al. 201054 in-vitro extracted teeth assessment of apically

extruded debris

Taha et al. 201055 in-vitro extracted teeth histological sections (debris)

Fornari et al. 201056 in-vitro extracted teeth histological sections (debris)

Arya et al. 201157 in-vitro extracted teeth histological sections (debris)

Burklein and Schafer 201258 in-vitro extracted teeth assessment of apically extruded debris

Chandra et al. 201359 in-vitro extracted teeth SEM (debris)

De-Deus et al. 201436 in-vitro extracted teeth micro-CT (debris)

Parameters used to evaluate root canal preparation 127

� For shaping ability: flow, taper, smoothness of the walls,original canal shape, changes in curvature angulation,

apical transportation, canal area, centering ratio, thick-ness of remaining root structure, working time, fracturedinstruments, aberrations and working length.

Table 1 shows in-vitro studies evaluating the cleaning

ability of instrumentation using extracted teeth:Table 2 shows studies evaluating the shaping ability of

instrumentation:

Discussion

The understanding of endodontic therapy concepts leadsto great advance in instruments and techniques, which is the

reason why, many studies to assess the performance andquality of these instruments and techniques have beenundertaken.

It has been noted that studies using extracted teeth toevaluate the quality of root canal instrumentation were morethan their counterparts using simulated canals in resin blocks.

The major advantage of extracted human teeth is toreproduce the clinical situation. However, it is difficult tostandardize some variables such as root canal length andwidth, dentine hardness, calcification and pulp stones, loca-

tion and nature of canal curvatures.13

On the other hand, simulated resin root canals allowstandardization of degree, location and radius of root canal

curvature in three dimensions as well as the tissue hardnessand the width of the root canals.

Superimposition techniques of pre- and post-operative

root canal outlines can be easily applied to these models,thus facilitating measurement of deviations at any point ofthe root canals using PC-based measurement (comparison

among parameters recorded as data in computer) or sub-traction radiography. This model guarantees a high degree ofreproducibility and standardization of the experimentaldesign.77 It has been suggested that the results of such studies

may be transferred to human teeth.77

Nevertheless, some concern has been expressed regardingthe differences in hardness between dentine and resin.Microhardness of dentine has been measured as 35e40 kg/mm2 near the pulp space, while the hardness of resin mate-

rials used for simulated root canals is estimated to rangefrom 20 to 22 kg/mm2 depending on the material used.78,79

For the removal of natural dentine, double the force had

to be applied than that for resin.77 Additionally, criticsreported that the size of resin chips and natural dentinechips may not be identical, resulting in frequent blockages

of the apical root canal space and difficulties to remove thedebris in resin canals.77 In consequence, data on workingtime and working safety from studies using resin blocks

may not be transferable to the clinical situation.13

Most studies on post-operative root canal shape orchanges in root canal morphology, have been performed inmesial root canals of mandibular molars,24,30,32,67,73,74 as

these teeth in most cases show a curvature at least in themesioedistal plane.80 On the other hand, other studiesused mandibular premolars,52,55,57,66 mandibularincisors,18

maxillary incisors50 or maxillary molars.81,82

The studies on root canal curvature have shown thatseveral techniques were conducted to describe canal curva-

tures. Schneider angle was routinely used. Schneider tech-nique mainly emphasizes the canal curvature in the apicalregion, and Weine technique considers the apical region, andthe LA technique considers only the apical curvature of the

canal and does not evaluate the overall root canal curvature.CAA together with height and distance of curvature providemore information about the coronal geometry of root canal

curvatures.38 Few studies have used Schneider angle incombination with the radius of curvature.83e85 Othersclaimed that the shape of root canal curve is more

accurately described using Schneider in combination withCAA and the related parameters including radius, length,distance and height of curvature. This combination

provides more accurate guidelines for both coronal andapical parts of canal curvature.86

Lately, many investigators have been more concernedwith micro-computed tomography technique and its

Table 2: Studies evaluating the shaping ability of instrumentation.

Reference

(chronologic order)

Type of study

in-vitro, ex-vivo,

clinical

Samples Methodology/parameters

Schneider 197139 in-vitro extracted teeth cross sections (shaped form)

Jungmann et al. 197560 in-vitro extracted teeth cross sections (shaped form)

Abou-Rass et al. 198261 in-vitro extracted teeth silicone impressions (apical design, aberration removal, flow, taper,

uniformity, and smoothness of preparation)

Stadler et al. 198662 clinical patients radiographic analysis (breakage, lateral deviation, overfilling, root

perforation, Loss in working length).

Southard et al. 198763 in-vitro extracted teeth drawings and projected radiographic images (original canal shape)

Luiten et al. 199517 in-vitro extracted teeth Radiographs and computer analysis (Canal enlargement, apical

transportation)

Deplazes et al. 200126 in-vitro extracted teeth muffle system (canal area, centering ratio)

Gluskin et al. (2001)24 in-vitro extracted teeth CT scans Image analysis (canal area, canal transportation thickness

of remaining root structure, working time)

Schafer &

Lohmann 200264in-vitro simulated canals images and computer analysis (working time, canal transportation,

fractured instruments)

Song et al. 200465 in-vitro extracted teeth muffle system, modified formulas (centering ratio)

Guelzow et al. 200566 in-vitro extracted teeth muffle system, computer analysis (degree of curvature, working

length, straightening of curved root canals, working time, time for

changing the instruments)

Veltri et al. 200567 in-vitro extracted teeth radiographic analysis/Wiene, angle (shaping ability, working time,

canal form, working safety)

Mahran &

AboEl-Fotouh 20082in-vitro extracted teeth micro-CT (cervical dentin thickness, Canal volume)

Cheung & Cheung 200835 in-vitro extracted teeth micro-CT (canal diameter, remaining thickness of the dentin wall)

Vahid et al. 200968 ex-vitro extracted teeth radiographic analysis/Schneider’s angle (working time, canal

curvature, working length)

Moore et al. 200969 in-vitro extracted teeth micro-CT (amount of dentine removed, canal roundness,

transportation correlation between prepared apical root canal and

final instrument used)

Unal et al. 200970 in-vitro extracted teeth muffle system, images and radiographic analysis/Schneider’s angle,

formulas (dentine removed, transportation, working time, amount

of dentin removed, working length)

Ersev et al. 201022 in-vitro simulated canals images and computer analysis (amount of material removal, canal

transportation, centering ratio, aberrations)

Plotino et al. 201071 in-vitro simulated canals images analysis (angle and radius of the curvature, position of the

center of the curvature)

Hartmann et al. 201172 in-vitro extracted teeth micro-CT (canal transportation)

Alves Vde 201273 in-vitro extracted teeth Radiographs and computer analysis (canal aberration, apical

transportation)

Hashem et al. 201274 in-vitro extracted teeth CT scans Image analysis (canal transportation, centering ratio)

Ba-Hattab et al. 201375 in-vitro simulated canals images and computer analysis (working time canal transportation,

amount of removal resin)

Celik et al. 201376 in-vitro extracted teeth Radiographs and computer analysis (working length, canal

transportation)

A.A. Habib et al.128

breakthroughs (multislice computed tomography, cone-

beam computed tomography). A major factor for thisconcern is that the radiographs are two-dimensional repre-sentations for three-dimensional structures causing certainanatomical features not to be reflected in radiographic

changes. In the late 1980s, radiographs were digitized toprovide control over the quality of the film and reduce theradiation dosage. These digitized radiographs have an

advantage of controlling contrast and brightness by theoperator,87 although they still provide a 2-dimentional pic-ture. Conversely, micro-CT provides a 3-dimentional pic-

ture. It allows pre-instrumentation and post-instrumentationmeasuring of several parameters to evaluate the quality ofroot canal instrumentation techniques without using

complicated procedures, destructive sectioning of the speci-

mens, or loss of the root material during sectioning. Thereare no instrumentation problems passing through sections oraround curvatures that could affect the instrumentationoutcomes. Also, CT scans allow easy measurement of canal

changes, because each image has an accurate scale,decreasing the potential of a radiographic orphotographictransfer error.88 However, a cone-beam computed tomog-

raphy scan can expose the patient to two to eight times moreradiation than that of a panoramic radiograph and aboutone third of a full mouth radiographic series.89 It should also

be noted that cone-beam computed tomography scanningneeds complex devices,90 and is more expensive thanperiapical and panoramic radiography.

Parameters used to evaluate root canal preparation 129

Conclusion

1) Deep understanding of the phase of root canal instru-mentation leads to the use of several parameters to assess

post-operative shape or changes in root canalmorphology.

2) Shaping ability of the root canal instrumentation tech-niques has captured more researches compared with

cleaning ability.3) More attention must betaken regarding entire angular

changes by combining both Schneider and CAA methods

and their variabilities.4) More concern regarding micro-computed tomography

technique has been expressed as, this non-destructive

technique provides a 3-dimentional picture, and allowspre- and post-instrumentation measuring of several pa-rameters. We, therefore, conclude that, currently, themicro-computed tomography technique is a superior

methodology to evaluate the quality of root canalinstrumentation techniques.

Authors’ contributions

All authors contributed in collecting and classficating

papers. Dr. Adnan Asaad Habib wrote the text of the paperand was the corresponding author. Dr. Mazen Ibrahim Tahadesigned the figures.

Conflict of interest

The authors have no conflict of interest to declare.

Acknowledgment

The staff of Aleppo University, faculty of dentistry.

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