the advent of computed tomography ( ct ) has started a revolution of information in health 
 studies and has contributed to planning , diagnosis , treatment , and prognosis analysis of 
 several diseases .
cone - beam computed 
 tomography ( cbct ) is a recently developed technology with potential for 
 applications in different areas of research and clinical dentistry . in endodontics ,
conventional radiographic images provide a two - dimensional ( 2d ) rendition of 
 a three - dimensional ( 3d ) structure , which may result in interpretation errors .
periapical lesions of endodontic origin may be present but not visible on conventional 
 2d radiographs .
these lesions 
 are visible more often on cbct images , and new methods using cbct scans to investigate 
 apical periodontitis and root resorption have been developed , as new imaging 
 tools are now used in several endodontic research areas
artifacts can cause low image 
 quality and poor image contrast leading to limited interpretation of the 3d volumes . 

there is a concern with artifacts and the search for beam hardening corrections have 
 been the focus of several studies . according to ketcham and carlson 
 ( 2001 ) beam hardening
beam 
 hardening causes the edges of an object to appear as cupping , streaks , dark bands , or 
 flare artifacts , and is caused by preferential absorption of low - energy photons by 
 absorbing materials with higher atomic numbers ( e.g. metals ) .
( 2006 ) related that the 
 cbct image defects often appeared in images of solid non anatomical objects placed on 
 the dental arch , such as diagnostic stents ( guide splint ) for the accurate positioning 
 of dental implants and rectangular radiopaque reference markers for the assessment of 
 periodontal disease .
this was more frequent when radiopaque materials , such as 
 hydroxyapatite containing resin and aluminum , were used .
it is essential to understand , however , that image artifacts are likely to occur because 
 of the density of several materials used in root canal treatment . alterations from true 
 dimension of rcf may offer false interpretation on real dentin remnants .
thus , 
 evaluating the dimension of endodontic materials on cbct images may warn the clinicians 
 about the potential risks of misdiagnosis .
this study evaluated the discrepancy of rcf 
 measurements obtained from original root specimens and cbct images .
seventy - two human maxillary anterior teeth , extracted for different reasons , were 
 obtained from the dental urgency service of the federal university of gois - school 
 of dentistry , goinia , go , brazil .
this study was approved by the ethics committee of 
 the federal university of gois , brazil .
preoperative radiographs of each tooth were 
 taken to confirm the absence of calcified root canal , internal or external 
 resorption , and the presence of a fully formed apex .
the teeth were removed from storage in 0.2% thymol solution and immersed in 5% sodium 
 hypochlorite ( fitofarma , goinia , go , brazil ) for 30 min to remove external organic 
 tissues .
the crowns were removed to set the remaining tooth length to a standardized 
 13 mm from the root apex . after taking the initial radiographs , standard access 
 cavities were prepared , and the cervical third of each root canal was enlarged using 
 iso # 50 up to # 90 gates - glidden drills ( dentsply / maillefer , ballaigues , switzerland ) . 

teeth were prepared up to an iso#50k - file ( dentsply / maillefer ) 1 mm short of the 
 apical foramen . during instrumentation ,
the root canals were irrigated with 3 ml of 
 1% naocl ( fitofarma ) at each change of files .
root canals were dried and filled with 
 17% edta ( ph 7.2 ) ( biodinmica , ibipor , pr , brazil ) for 3 min to remove the smear 
 layer .
after that , the root canals were irrigated again with 3 ml of 1% naocl , and 
 dried with paper points ( dentsply / maillefer ) .
the teeth were randomly divided into 8 experimental groups with 9 specimens each , 
 according to different sealers : group 1 - sealapex ( sybron endo , 
 glendora , ca , usa ) ; group 2 - sealapex + gutta - percha points 
 ( dentsply / maillefer ) ; group 3 - sealer 26 ( dentsply ind .
, 
 petrpolis , rj , brazil ) ; group 4 - sealer 26+gutta - percha points ; group 5 
 - ah plus ( dentsply / maillefer ) ; group 6 - ah 
 plus+gutta - percha points ; group 7 - grossman sealer ( endofill , 
 dentsply ) ; group 8 - grossman sealer+gutta - percha points .
the chemical composition of sealers used are : sealapex ( calcium oxide , bismuth 
 trioxide , zinc oxide , sub - micron silica , titanium dioxide , zinc stearate , tricalcium 
 phosphate , and blend - ethyl toluene sulfonamide , polymethylenemethylsalicylate 
 resin , isobutyl salicylate and a pigment ) ; sealer 26 ( bismuth trioxide , calcium 
 hydroxide , tetraminehexamethilene , titanium dioxide and bisphenol epoxy resin ) ; ah 
 plus ( paste a - epoxy resins , calcium tungstate , zirconium oxide , silica , iron oxide 
 pigments , and paste b - amines , calcium tungstate , zirconium oxide , silica , silicone 
 oil ) ; grossman sealer ( zinc oxide , hydrogenated resin , bismuth subcarbonate , barium 
 sulfate , sodium borate , eugenol and almond oil ) . after root canal preparation , groups 1 ,
3 , 5 , and 7 were filled with the 
 corresponding sealers prepared according to the manufacturer 's directions and taken 
 using a lentulo spiral . in groups 2 , 4 , 6 , and 8
, teeth were filled with the 
 corresponding sealer and gutta - percha points using the conventional lateral 
 condensation technique .
the teeth were wrapped in wet gauze and placed in an 
 incubator at 37c for 72 h to allow complete set of the root canal filling materials . 

the coronal and the apical portion of the teeth were rendered waterproof with a layer 
 of cyanoacrylate adhesive ( super bonder , itapevi , sp , brazil ) to protect against the 
 influence of the water on materials .
teeth were positioned in the center of a bucket filled with water to simulate soft 
 tissue and supported by a plastic platform , based on the model used in previous 
 studies .
cbct 
 images were acquired with the first generation i - cat cone beam 3d imaging system 
 ( imaging sciences international , hatfield , pa , usa ) .
exposure time was 40 s. after obtaining the cbct scans , the roots of all teeth were carefully sectioned in 
 axial , sagittal or coronal planes using a high - speed endo z bur ( dentsply / maillefer ) 
 under water spray cooling .
the axial cuts were obtained at 6.5 mm from the root apex ; 
 and for sagittal and coronal planes , the roots were sectioned longitudinally , in the 
 center of the root canal ( figure 1 )
. schematic representation of sectioning root method and post length , showing the 
 sagittal , axial , and coronal views all measurements of the sectioned roots were made by two endodontists using a digital 
 caliper accurate to 0.01 mm ( fowler / sylvac ultra - cal mark iv electronic caliper , 
 crissier , switzerland ) .
the calibrated examiners measured all the specimens and cbct 
 images , and assessed rcf dimensions in the directions described below .
all measurements made on the cbct images were acquired by two dental radiology 
 specialists with the scanner 's proprietary software ( xoran version 3.1.62 ; xoran 
 technologies , ann arbor , mi , usa ) in a pc workstation running microsoft windows xp 
 professional sp-2 ( microsoft corp , redmond , wa , usa ) , with processor 
 intelcore 2 duo-6300 1.86 ghz ( intel corporation , usa ) , 
 nvidia geforce 6200 turbo cache videocard ( nvidia corporation , usa ) and monitor eizo 
 - flexscan s2000 , resolution 1600x1200 pixels ( eizo nanao corporation hakusan , 
 japan ) .
all cbct scans were reformatted using 0.2 mm , 0.6 mm , 1.0 mm , 3.0 mm and 5.0 
 mm slice thickness . to determine the discrepancy between the rcf measurements made on the original root 
 specimens and those made on the cbct images , the same sites were evaluated on the 
 cbct scans using the same orientation ( axial , sagittal and coronal ) . in all planes , 

on axial images , the rcf 
 measurement was made in the buccal / palatal direction ; on sagittal images , in the 
 mesial / distal direction ; and on coronal images , in the buccal / palatal direction .
one - way analysis of variance ( anova ) and tukey tests were used for statistical 
 analyses .
seventy - two human maxillary anterior teeth , extracted for different reasons , were 
 obtained from the dental urgency service of the federal university of gois - school 
 of dentistry , goinia , go , brazil .
this study was approved by the ethics committee of 
 the federal university of gois , brazil .
preoperative radiographs of each tooth were 
 taken to confirm the absence of calcified root canal , internal or external 
 resorption , and the presence of a fully formed apex .
the teeth were removed from storage in 0.2% thymol solution and immersed in 5% sodium 
 hypochlorite ( fitofarma , goinia , go , brazil ) for 30 min to remove external organic 
 tissues .
the crowns were removed to set the remaining tooth length to a standardized 
 13 mm from the root apex . after taking the initial radiographs , standard access 
 cavities were prepared , and the cervical third of each root canal was enlarged using 
 iso # 50 up to # 90 gates - glidden drills ( dentsply / maillefer , ballaigues , switzerland ) . 

teeth were prepared up to an iso#50k - file ( dentsply / maillefer ) 1 mm short of the 
 apical foramen . during instrumentation ,
the root canals were irrigated with 3 ml of 
 1% naocl ( fitofarma ) at each change of files .
root canals were dried and filled with 
 17% edta ( ph 7.2 ) ( biodinmica , ibipor , pr , brazil ) for 3 min to remove the smear 
 layer .
after that , the root canals were irrigated again with 3 ml of 1% naocl , and 
 dried with paper points ( dentsply / maillefer ) .
the teeth were randomly divided into 8 experimental groups with 9 specimens each , 
 according to different sealers : group 1 - sealapex ( sybron endo , 
 glendora , ca , usa ) ; group 2 - sealapex + gutta - percha points 
 ( dentsply / maillefer ) ; group 3 - sealer 26 ( dentsply ind .
, 
 petrpolis , rj , brazil ) ; group 4 - sealer 26+gutta - percha points ; group 5 
 - ah plus ( dentsply / maillefer ) ; group 6 - ah 
 plus+gutta - percha points ; group 7 - grossman sealer ( endofill , 
 dentsply ) ; group 8 - grossman sealer+gutta - percha points .
the chemical composition of sealers used are : sealapex ( calcium oxide , bismuth 
 trioxide , zinc oxide , sub - micron silica , titanium dioxide , zinc stearate , tricalcium 
 phosphate , and blend - ethyl toluene sulfonamide , polymethylenemethylsalicylate 
 resin , isobutyl salicylate and a pigment ) ; sealer 26 ( bismuth trioxide , calcium 
 hydroxide , tetraminehexamethilene , titanium dioxide and bisphenol epoxy resin ) ; ah 
 plus ( paste a - epoxy resins , calcium tungstate , zirconium oxide , silica , iron oxide 
 pigments , and paste b - amines , calcium tungstate , zirconium oxide , silica , silicone 
 oil ) ; grossman sealer ( zinc oxide , hydrogenated resin , bismuth subcarbonate , barium 
 sulfate , sodium borate , eugenol and almond oil ) . after root canal preparation , groups 1 ,
3 , 5 , and 7 were filled with the 
 corresponding sealers prepared according to the manufacturer 's directions and taken 
 using a lentulo spiral . in groups 2 , 4 , 6 , and 8
, teeth were filled with the 
 corresponding sealer and gutta - percha points using the conventional lateral 
 condensation technique .
the teeth were wrapped in wet gauze and placed in an 
 incubator at 37c for 72 h to allow complete set of the root canal filling materials . 

the coronal and the apical portion of the teeth were rendered waterproof with a layer 
 of cyanoacrylate adhesive ( super bonder , itapevi , sp , brazil ) to protect against the 
 influence of the water on materials .
teeth were positioned in the center of a bucket filled with water to simulate soft 
 tissue and supported by a plastic platform , based on the model used in previous 
 studies .
cbct 
 images were acquired with the first generation i - cat cone beam 3d imaging system 
 ( imaging sciences international , hatfield , pa , usa ) .
after obtaining the cbct scans , the roots of all teeth were carefully sectioned in 
 axial , sagittal or coronal planes using a high - speed endo z bur ( dentsply / maillefer ) 
 under water spray cooling .
the axial cuts were obtained at 6.5 mm from the root apex ; 
 and for sagittal and coronal planes , the roots were sectioned longitudinally , in the 
 center of the root canal ( figure 1 )
. schematic representation of sectioning root method and post length , showing the 
 sagittal , axial , and coronal views
all measurements of the sectioned roots were made by two endodontists using a digital 
 caliper accurate to 0.01 mm ( fowler / sylvac ultra - cal mark iv electronic caliper , 
 crissier , switzerland ) .
the calibrated examiners measured all the specimens and cbct 
 images , and assessed rcf dimensions in the directions described below .
all measurements made on the cbct images were acquired by two dental radiology 
 specialists with the scanner 's proprietary software ( xoran version 3.1.62 ; xoran 
 technologies , ann arbor , mi , usa ) in a pc workstation running microsoft windows xp 
 professional sp-2 ( microsoft corp , redmond , wa , usa ) , with processor 
 intelcore 2 duo-6300 1.86 ghz ( intel corporation , usa ) , 
 nvidia geforce 6200 turbo cache videocard ( nvidia corporation , usa ) and monitor eizo 
 - flexscan s2000 , resolution 1600x1200 pixels ( eizo nanao corporation hakusan , 
 japan ) .
all cbct scans were reformatted using 0.2 mm , 0.6 mm , 1.0 mm , 3.0 mm and 5.0 
 mm slice thickness . to determine the discrepancy between the rcf measurements made on the original root 
 specimens and those made on the cbct images , the same sites were evaluated on the 
 cbct scans using the same orientation ( axial , sagittal and coronal ) . in all planes , 

on axial images , the rcf 
 measurement was made in the buccal / palatal direction ; on sagittal images , in the 
 mesial / distal direction ; and on coronal images , in the buccal / palatal direction .
one - way analysis of variance ( anova ) and tukey tests were used for statistical 
 analyses .
the variation of rcf dimensions on cbct images 
 ranged from 9% to 100% greater than those measured on the original root specimens .
the 
 lowest rcf dimensions ( percentage values ) corresponded to sealer 26 and sealer 26 plus 
 gutta - percha points .
groups that were filled with sealers alone showed the greatest 
 dimensional values in cbct images when compared with groups filled with sealer and 
 gutta - percha points , with statistically significant difference among the groups . when 
 slice thicknesses varying from 0.2 mm to 5.0 mm were measured , an increase of 46.16% to 
 50.53% in rcf dimensions
the 
 different visualization planes analysis revealed an increase in rcf dimensions ranging 
 from 35.48% ( sagittal slice ) to 59.28% ( axial slice ) ( with statistically significant 
 difference ) .
figures 2 - 3 illustrate the sagittal , axial and coronal views of the rcf using 
 cbct . percentage ( % ) of root canal filling dimension increase from original specimens to 
 cone - beam computed tomography images according to slice thickness and planes for 
 each endodontic material ( =5% ) interaction between type of cut and slice thickness significantly by tukey 
 test .
gpp - gutta - percha points percentage ( % ) of root canal filling dimension increase from original specimens to 
 cone - beam computed tomography images for each group according to sealers , slice 
 thickness and planes , and statistical analysis ( =5% ) different letters in horizontal demonstrate statistically significant 
 difference with p<0.05 .
* p=0.0001 by anova test and p=0.0001 by tukey 
 test ; p=0.647 by anova test and p=0.272 by tukey test ; p=0.0001 by anova test and p=0.0001 by tukey test . gpp - gutta - percha 
 points .
cone - beam computed tomography images of root canal filling with sealapex ( a ) , 
 sealapex+gutta - percha ( b ) , sealer 26 ( c ) , and sealer 26+gutta - percha ( d ) in 
 different slice thickness and planes ( sagittal , axial and coronal ) cone - beam computed tomography images of root canal filling with grossman sealer 
 ( a ) , grossman sealer 26+gutta - percha ( b ) , ah plus ( c ) , and ah plus+gutta - percha 
 ( d ) in different slice thickness and planes ( sagittal , axial and coronal )
a new standard of contemporary endodontics has been created with the advent of 
 cbct . for several 
 years , rcf quality was evaluated in clinical practice according to a 2d image of 3d 
 structures .
the radiographic appearance of the filled root canal 
 space is used to evaluate its sealing quality and to indicate the presence of apical 
 periodontitis .
however , the limitations of a radiographic assessment as a reference and 
 study method have been demonstrated in several studies . there is a possibility of interference from artifact caused by different densities from 
 endodontic materials , which can cause errors of interpretation .
our main purpose was to 
 determine the discrepancy of rcf measurements between original root specimens and cbct 
 images , and our findings showed that measurements obtained from cbct images of rcf with 
 sealers and sealers plus gutta - percha were greater than those obtained on the original 
 root specimens ( tables 1 and 2 ) .
these results bring important implications for 
 the clinical evaluation of rcf and anatomic dental structures .
special attention should 
 be paid depending on the density of the endodontic material and slice 
 thickness / orientation which can lead to misdiagnosis .
( 2008 ) compared the accuracy of cbct and 
 multislice ct for linear jaw bone measurements , and found that both methods were 
 accurate when used to evaluate an ex vivo specimen .
( 2008 ) determined the 
 geometric accuracy of cbct scans in comparison with a multidetector computed tomography 
 ( mdct ) scanner .
their results showed that the cbct devices provide satisfactory 
 information about linear distances and volumes .
mdct scans proved slightly more accurate 
 in both measurement categories , but this difference may be irrelevant for most clinical 
 applications .
recent studies using cbct images detected voids in root filling 
 and incomplete removal of filling material during endodontic retreatment .
( 2007 ) showed that image 
 quality of storage phosphor images was subjectively as good as conventional film images 
 and superior to limited - volume cbct images for the evaluation of both homogeneity and 
 length of root fillings in single - rooted teeth .
( 2009 ) analyzed voids in root fillings 
 using intraoral analogue , intraoral digital and cbct images .
voids larger than 30 m 
 were detected by all imaging techniques . for small void detection , all digital intraoral 
 techniques performed better than intraoral analogue and cbct images .
the difference in density of rcf materials may have affected the results of several 
 studies , and was also found in our specimens .
the endodontic 
 sealers and gutta - percha used in our study have different physical and chemical 
 properties because of different radiopaque substances ( bismuth oxide , barium sulfate , 
 zinc oxide ) .
( 2011 ) 
 evaluated the effect caused by intracanal posts ( glass - fiber post , carbon fiber root 
 canal , pre - fabricated post - metal screws , silver alloy post and gold alloy post ) on the 
 dimensions of cbct images of endodontically treated teeth .
gold alloy and silver alloy 
 post dimensions were greater on cbct scans than on the original root specimens .
cbct reconstructions may show higher rcf dimensional values , as well as lack of image 
 homogeneity and definition .
( 2007 ) conducted an in vitro study about the 
 effect of projection data discontinuity - related artifacts in limited - volume cbct imaging 
 of jaws .
the effects of artifacts were scored as the difference in relative density 
 between the lingual and buccal soft tissue .
the intensity of artifacts increased when 
 more objects were outside the area being imaged .
fewer artifacts were noted in images 
 produced by the particular flat cbct panel detector used in this investigation . 

( 2009 ) analyzed 
 the relationship between density values and cbct volume size using an alphard cbct 
 system capable of providing different - size imaging volumes .
the authors found that the 
 data discontinuity - related effect was different in limited - volume cbct scanning .
considering that the higher density of rcf materials may produce image artifacts , 
 special attention should be paid to the rcf evaluation of endodontically treated teeth . 

any change from true dimension of rct may favor false interpretation on real dentin 
 remnants , and constitute potential risks of misdiagnosis .
the implication of density 
 artifacts on diagnostic procedures seems to be obvious , and different correction methods have been 
 investigated .
( 2008 ) studied the effect of incident radiation energy on the 
 amount and extent of image artifacts over adjacent anatomic structures .
the use of a 
 harder energy beam during scanning appears to result in less extensive artifact 
 formation .
a strong correlation between gray scale values on cbct images and bone densities has 
 been found by haristoy , et al . 

this has implications for potential quantitative radiological approaches to 
 determine bone density from cbct images .
however , given the variation of gray scale 
 values despite normalization , it may be necessary to use calibration phantoms scanned 
 simultaneously with the patient to ensure an accurate determination of bone 
 density . hunter and 
 mcdavid ( 2009 )
showed that 
 additional copper filtration suppresses beam hardening artifacts . in micro - computed 
 tomography scanning based on bone mineral density measurements , the effects of beam 
 hardening - induced cupping artifacts may be also minimized by beam filtration .
cbct provides a three - dimensional image , in which a new plane has been added : depth .
its 
 clinical application results in greater accuracy and may be used in nearly all areas of 
 dentistry : surgery , implants , dentistry , orthodontics , endodontics , periodontics , 
 temporomandibular dysfunction , image diagnosis , and so on .
few studies investigated the dimensional alterations of endodontic materials observed on 
 cbct images , and further studies should include other variables , such as the effect of 
 artifacts on intracanal post alloys .
the evolution of the new softwares certainly can 
 reduce metallic artifact and dimensional alterations in future reconstructions of cbct 
 images .
periapical radiographs should be used as a reference standard , together with 
 cbct image interpretation , when making endodontic diagnoses .
the results of this study showed that rcf dimensions were greater on cbct images than on 
 the original root specimens , especially when only sealer was used .
 objective to evaluate the discrepancy of root canal filling ( rcf ) measurements obtained 
 from original root specimens and cone - beam computed tomography ( cbct ) images . 
 material and methods seventy - two human maxillary anterior teeth were prepared up to an iso # 50 k - file 
 1 mm short of the apical foramen . 
 thus , the teeth were randomly divided into 8 
 groups , according to the root canal filling material : sealapex , 
 sealapex+gutta - percha points , sealer 26 , sealer 
 26+gutta - percha points , ah plustm , ah plustm+gutta - percha points , 
 grossman sealer , and grossman sealer+gutta - percha points . 
 after root canal 
 preparation and rcf , cbct scans were acquired and the specimens were sectioned in 
 axial , sagittal and coronal planes . 
 the rcf measurements were obtained in 
 different planes and thicknesses to determine the discrepancy between the original 
 root specimens ( using a digital caliper ) and the cbct images ( using the scanner 's 
 proprietary software ) . 
 one - way analysis of variance and tukey tests were used for 
 statistical analyses . 
 the significance level was set at =5% . 
 results measurements of the different endodontic filling materials were 9% to 100% 
 greater on the cbct images than on the original root specimens . 
 greater rcf 
 dimensions were found when only sealers were used , with statistically significant 
 difference among the groups . 
 conclusions rcf dimensions were greater on cbct images than on the original root specimens , 
 especially when only sealer was used . 
INTRODUCTION
MATERIAL AND METHODS
Tooth preparation
CBCT image acquisition
Sectioning of roots
Measurement of specimens and CBCT slices
RESULTS
DISCUSSION
CONCLUSIONS