the assessment of root canal therapy in order to determine whether retreatment is needed 
 constitutes a frequent and difficult task for clinicians , especially when patient 's 
 signs and symptoms are not evident .
conventional periapical radiography is the most commonly used method for evaluating the 
 technical quality of filled root canals .
buccolingual radiographs are generally accepted to have limited 
 value for root canal quality assessments .
nevertheless , since 
 this is the only objective non - invasive method for assessing root canal fillings , 
 current evidence on endodontic treatment outcome is solely derived from follow - up 
 studies that rely basically on this method .
root canal fillings can be distinguished on radiographs because the sealing materials 
 must have some degree of radiopacity , provided that it is above that of dentin and 
 bone .
as the sealer is used together with gutta - percha for root canal 
 filling , its type and thickness may have a significant effect on the radiographic 
 appearance of the obturated canal .
it is postulated that the use of a 
 sealer with greater radiopacity might give the impression of a compact filling , despite 
 the presence of gross imperfections . on the other hand ,
a less radiopaque material might 
 be judged absent in areas where it is actually present in small amounts . 
 among the resin - based sealers
commercially available , results from recent in 
 vitro investigations indicate that ah plus is twice as radiopaque as 
 acroseal .
radiographic void detection is clinically important for prognosis determination since 
 cross - sectional investigations have correlated the presence of filling voids with apical 
 periodontitis .
therefore , this study aimed to investigate if any of 
 two radiopaque resin - based sealers blurred the observers ' ability to detect root canal 
 filling voids during radiographic analysis .
for this study , 48 permanent maxillary canines with single straight or slightly 
 curved root canals ( 252 mm ) were selected and stored in 0.5% saline solution after 
 approval of the research project by the university of so paulo 's research ethics 
 committee ( protocol # 153/2005 ) . after standard access ,
root canal lengths were 
 assessed by placing a size 15 k file ( dentisly , dentsply / maillefer , ballaigues , 
 switzerland ) inside the canal until the tip perforated through the apical foramen . 

all canals were 
 instrumented using a push - pull filing technique up to file size 55 . after every 
 instrument withdrawal from the root canal , full irrigation with 1% sodium 
 hypochlorite was performed .
apical foramen enlargement was done with a 25 k file . after a 3-min final irrigation 
 with 17% edta ( biodinmica , biodinmica qumica e farmacutica ltda . ,
ibipor , pr , 
 brazil ) , the root canals were rinsed with 0.5% saline and dried thoroughly with paper 
 points .
the samples were divided into three groups , and each group was laterally condensed 
 with one of the following epoxy resin - based sealers : ah plus ( dentsply , 
 dentsply detrey gmbh , konstanz , germany ) , acroseal(septodont , specialits 
 septodont , saint - maur - des - fosss , france ) and an experimental non - radiopaque sealer 
 ( nrs ) used as a control . ah plus and acroseal were measured and mixed at a ratio of 
 1:1 paste / paste , according to the manufacturer 's recommendations . for the 
 experimental nrs , 1 part of catalyst ( resin hardener )
was added to 2 parts of 
 resinous base ( epoxy resin and polyurethane polyol ) , and then the mixture was 
 homogenized for 15 s. before being filled with lateral condensation , a radiolucent nylon fishing line ( 0.25 
 mm in diameter and 20 cm in length ) ( tople on , tople , hong kong , china ) 
 was inserted into the root canal of half of the specimens of each group ( n=8 ) . both 
 ends of the string were tied in alignment to a device , such that moving the tooth 
 distally would put the stretched fishing line into contact with the mesial wall of 
 the root canal through the entire filling procedure .
the sealer was taken to the root canals by coating the appropriate master 
 gutta - percha cone .
a # 30 master cone was used in root canals that received the nylon 
 thread , whereas a # 55 master cone was inserted into the remaining root canals .
the 
 master cone was laterally condensed with a and b finger spreaders ( dentsply , 
 dentsply - maillefer , ballaigues , switzerland ) , and 7 - 9 accessory cones ( tanari r7 , 
 tanari , manacapuru , am , brazil ) were added .
all filling 
 procedures were conducted by a single operator with five years of clinical experience 
 in endodontics .
radiographs of each canine were obtained in the buccolingual direction using the 
 paralleling technique .
the tooth was fixed into the canine bone alveolus of a phantom 
 built from a dry human maxilla acrylic - coated for soft tissue simulation .
each 
 periapical e film ( insight ; kodak co. , rochester , ny , usa ) was maintained in a 
 constant position during radiographic exposure through insertion in the acrylic slot 
 shaped in the vault of the palate .
the phantom was positioned in front of the x - ray tube with a specifically designed 
 resinous device .
all radiographic exposures were completed with a dental x - ray unit 
 ( x 70 ; dabi atlante , ribeiro preto , sp , brazil ) at 70 kvp and 8 ma .
the exposure 
 time was 0.5 s , the focus - object distance was 40 cm and the object - to - receptor 
 distance was 2 cm . in a darkened room with temperature set at 21c the exposed films were immersed 
 together in the developer solution for 3 min at 21c and then rinsed with water for 
 10 s before being submerged in the fixer solution for 8 min .
the developed films were 
 subsequently washed with running water for 10 min and allowed to dry in a dust - free 
 atmosphere . to assure the same position of the fishing line for all teeth ,
the roots were 
 sectioned transversely with a 0.3-mm - thick diamond saw ( isomet 15hc , buehler , 
 buehler , lake bluff , illinois , usa ) at 300 rpm and the three resulting sections 
 observed under magnification to confirm the mesial position of the nylon string 
 ( figure 1 ) and the absence of major voids in 
 those teeth without artificial defect .
nine sectioned specimens in which the fishing 
 line was not in the expected position or presented major inherent voids were 
 replaced .  
apical cross section of the root canal filling showing the nylon thread used to 
 simulate the void ( arrow ) prior to image interpretation , a radiologist and an endodontist , who had not 
 performed any of the fillings , received written instructions about the test .
the 
 examiners were asked to scrutinize radiographic images for the presence of voids in 
 the mesial , middle and distal aspects of the root canal fillings , which were divided 
 imaginatively and equally into coronal , medium and apical thirds for organizational 
 purposes .
no information on filling preparation was provided , and examiners were 
 instructed to ignore the distance of fillings to the apex or any radiolucent area in 
 contact with the root . immediately after , a pair of radiographs with non - defective and defective fillings 
 served as models to demonstrate the appearance of voids to the examiners .
all radiographic assessments were performed with the aid of an ethyl - vinyl - acetate 
 mask positioned over a fluorescent cold lightbox ( medalight lp-400 , hong kong , china ) 
 in the same light - controlled room .
the 48 radiographs were numbered , mounted in a 
 random order and individually interpreted ( figure 
 2 ) .
the observers had no knowledge of the extent , location or distribution 
 of the voids .
representative radiographic images of defective root canal fillings assessed by 
 the examiners ( a  ah plus ; b  acroseal ; c  
 non - radiopaque sealer ) . note the appearance of simulated voids ( arrows ) analyses of images were recorded in a proper form , and the viewing time was 
 unlimited .
sensitivity refers to the proportion of root canal fillings correctly identified as 
 having a defect among a group of fillings that really had a simulated defect . to 
 calculate sensitivity ,
the mean number of defective fillings correctly identified for 
 each group in both evaluations was divided by the mean number of defective fillings 
 correctly identified ( true positives ) plus the mean number of false negative 
 results .
specificity refers to the proportion of root canal fillings correctly detected as not 
 having a defect among a group of fillings that did not have simulated defects . 

specificity of each group was determined by the mean number of non - defective fillings 
 correctly identified divided by the mean number of non - defective fillings correctly 
 identified ( true negative ) plus false positive results .
the differences in sensitivity and specificity values between groups and examiners 
 were compared using fisher 's exact and mcnemar 's tests , respectively , which were both 
 adjusted to the 95% confidence interval .
statistical evaluation for all tests was performed with 
 spss database software ( spss v.110 , spss inc . ,
for this study , 48 permanent maxillary canines with single straight or slightly 
 curved root canals ( 252 mm ) were selected and stored in 0.5% saline solution after 
 approval of the research project by the university of so paulo 's research ethics 
 committee ( protocol # 153/2005 ) . after standard access ,
root canal lengths were 
 assessed by placing a size 15 k file ( dentisly , dentsply / maillefer , ballaigues , 
 switzerland ) inside the canal until the tip perforated through the apical foramen . 

all canals were 
 instrumented using a push - pull filing technique up to file size 55 . after every 
 instrument withdrawal from the root canal , full irrigation with 1% sodium 
 hypochlorite was performed .
apical foramen enlargement was done with a 25 k file . after a 3-min final irrigation 
 with 17% edta ( biodinmica , biodinmica qumica e farmacutica ltda . ,
ibipor , pr , 
 brazil ) , the root canals were rinsed with 0.5% saline and dried thoroughly with paper 
 points .
the samples were divided into three groups , and each group was laterally condensed 
 with one of the following epoxy resin - based sealers : ah plus ( dentsply , 
 dentsply detrey gmbh , konstanz , germany ) , acroseal(septodont , specialits 
 septodont , saint - maur - des - fosss , france ) and an experimental non - radiopaque sealer 
 ( nrs ) used as a control . ah plus and acroseal were measured and mixed at a ratio of 
 1:1 paste / paste , according to the manufacturer 's recommendations . for the 
 experimental nrs , 1 part of catalyst ( resin hardener )
was added to 2 parts of 
 resinous base ( epoxy resin and polyurethane polyol ) , and then the mixture was 
 homogenized for 15 s. before being filled with lateral condensation , a radiolucent nylon fishing line ( 0.25 
 mm in diameter and 20 cm in length ) ( tople on , tople , hong kong , china ) 
 was inserted into the root canal of half of the specimens of each group ( n=8 ) . both 
 ends of the string were tied in alignment to a device , such that moving the tooth 
 distally would put the stretched fishing line into contact with the mesial wall of 
 the root canal through the entire filling procedure .
the sealer was taken to the root canals by coating the appropriate master 
 gutta - percha cone .
a # 30 master cone was used in root canals that received the nylon 
 thread , whereas a # 55 master cone was inserted into the remaining root canals .
the 
 master cone was laterally condensed with a and b finger spreaders ( dentsply , 
 dentsply - maillefer , ballaigues , switzerland ) , and 7 - 9 accessory cones ( tanari r7 , 
 tanari , manacapuru , am , brazil ) were added .
all filling 
 procedures were conducted by a single operator with five years of clinical experience 
 in endodontics .
radiographs of each canine were obtained in the buccolingual direction using the 
 paralleling technique .
the tooth was fixed into the canine bone alveolus of a phantom 
 built from a dry human maxilla acrylic - coated for soft tissue simulation .
each 
 periapical e film ( insight ; kodak co. , rochester , ny , usa ) was maintained in a 
 constant position during radiographic exposure through insertion in the acrylic slot 
 shaped in the vault of the palate .
the phantom was positioned in front of the x - ray tube with a specifically designed 
 resinous device .
all radiographic exposures were completed with a dental x - ray unit 
 ( x 70 ; dabi atlante , ribeiro preto , sp , brazil ) at 70 kvp and 8 ma .
the exposure 
 time was 0.5 s , the focus - object distance was 40 cm and the object - to - receptor 
 distance was 2 cm . in a darkened room with temperature set at 21c the exposed films were immersed 
 together in the developer solution for 3 min at 21c and then rinsed with water for 
 10 s before being submerged in the fixer solution for 8 min .
the developed films were 
 subsequently washed with running water for 10 min and allowed to dry in a dust - free 
 atmosphere . to assure the same position of the fishing line for all teeth ,
the roots were 
 sectioned transversely with a 0.3-mm - thick diamond saw ( isomet 15hc , buehler , 
 buehler , lake bluff , illinois , usa ) at 300 rpm and the three resulting sections 
 observed under magnification to confirm the mesial position of the nylon string 
 ( figure 1 ) and the absence of major voids in 
 those teeth without artificial defect .
nine sectioned specimens in which the fishing 
 line was not in the expected position or presented major inherent voids were 
 replaced .  
apical cross section of the root canal filling showing the nylon thread used to 
 simulate the void ( arrow )
prior to image interpretation , a radiologist and an endodontist , who had not 
 performed any of the fillings , received written instructions about the test .
the 
 examiners were asked to scrutinize radiographic images for the presence of voids in 
 the mesial , middle and distal aspects of the root canal fillings , which were divided 
 imaginatively and equally into coronal , medium and apical thirds for organizational 
 purposes .
no information on filling preparation was provided , and examiners were 
 instructed to ignore the distance of fillings to the apex or any radiolucent area in 
 contact with the root . immediately after , a pair of radiographs with non - defective and defective fillings 
 served as models to demonstrate the appearance of voids to the examiners .
all radiographic assessments were performed with the aid of an ethyl - vinyl - acetate 
 mask positioned over a fluorescent cold lightbox ( medalight lp-400 , hong kong , china ) 
 in the same light - controlled room .
the 48 radiographs were numbered , mounted in a 
 random order and individually interpreted ( figure 
 2 ) .
the observers had no knowledge of the extent , location or distribution 
 of the voids .
representative radiographic images of defective root canal fillings assessed by 
 the examiners ( a  ah plus ; b  acroseal ; c  
 non - radiopaque sealer ) .
note the appearance of simulated voids ( arrows ) analyses of images were recorded in a proper form , and the viewing time was 
 unlimited .
sensitivity refers to the proportion of root canal fillings correctly identified as 
 having a defect among a group of fillings that really had a simulated defect . to 
 calculate sensitivity ,
the mean number of defective fillings correctly identified for 
 each group in both evaluations was divided by the mean number of defective fillings 
 correctly identified ( true positives ) plus the mean number of false negative 
 results .
specificity refers to the proportion of root canal fillings correctly detected as not 
 having a defect among a group of fillings that did not have simulated defects . 

specificity of each group was determined by the mean number of non - defective fillings 
 correctly identified divided by the mean number of non - defective fillings correctly 
 identified ( true negative ) plus false positive results .
the differences in sensitivity and specificity values between groups and examiners 
 were compared using fisher 's exact and mcnemar 's tests , respectively , which were both 
 adjusted to the 95% confidence interval .
statistical evaluation for all tests was performed with 
 spss database software ( spss v.110 , spss inc . ,
in the assessment by the endodontist , the experimental groups had significantly lower 
 sensitivity values ( p<0.05 ) than the nrs group ( control ) at the coronal third of 
 the root canal fillings ( table 1 ) .
the 
 coronal portion of ah plus and acrosealfillings exhibited 
 significantly lower sensitivity values ( p<0.05 ) than the apical portion for both 
 examiners . in the control group , this difference was only observed in the assessment 
 by the radiologist . in comparison with the radiologist 's examination , significantly 
 higher sensitivity values ( p<0.05 ) for the endodontist 's evaluation of the nrs 
 ( cervical portion ) and ah plus ( middle portion ) groups were noted .
the sensitivity 
 values obtained in the middle portion of the root canal fillings were not 
 significantly different from those obtained in the coronal and apical portions 
 ( p>0.05 ) .
mean values and ranges of sensitivity in each third of the fillings assessed by 
 the examiners ( same letters indicate statistically significant difference at 
 5% ) in the radiologist 's evaluation , the coronal and apical portions of acroseal fillings 
 exhibited significantly higher values of specificity ( p<0.05 ) than the nrs group 
 ( control ) , whereas the endodontist 's assessment revealed significant differences 
 ( p<0.05 ) only for the apical portion ( table 
 2 ) . for all groups ,
the differences in specificity between the coronal and 
 apical portions of the root canal fillings were not statistically significant 
 ( p>0.05 ) , nor were the specificity values obtained in the middle portion in 
 comparison to the coronal and apical thirds ( p>0.05 ) .
mean values and ranges of specificity in each third of the fillings assessed by 
 the examiners ( same letters indicates statistically significant difference at 
 5% ) the intraobserver kappa values were 0.71 for the radiologist and 0.77 for the 
 endodontist .
in the assessment by the endodontist , the experimental groups had significantly lower 
 sensitivity values ( p<0.05 ) than the nrs group ( control ) at the coronal third of 
 the root canal fillings ( table 1 ) .
the 
 coronal portion of ah plus and acrosealfillings exhibited 
 significantly lower sensitivity values ( p<0.05 ) than the apical portion for both 
 examiners . in the control group , this difference was only observed in the assessment 
 by the radiologist . in comparison with the radiologist 's examination , significantly 
 higher sensitivity values ( p<0.05 ) for the endodontist 's evaluation of the nrs 
 ( cervical portion ) and ah plus ( middle portion ) groups were noted .
the sensitivity 
 values obtained in the middle portion of the root canal fillings were not 
 significantly different from those obtained in the coronal and apical portions 
 ( p>0.05 ) .
mean values and ranges of sensitivity in each third of the fillings assessed by 
 the examiners ( same letters indicate statistically significant difference at 
 5% )
in the radiologist 's evaluation , the coronal and apical portions of acroseal fillings 
 exhibited significantly higher values of specificity ( p<0.05 ) than the nrs group 
 ( control ) , whereas the endodontist 's assessment revealed significant differences 
 ( p<0.05 ) only for the apical portion ( table 
 2 ) .
for all groups , the differences in specificity between the coronal and 
 apical portions of the root canal fillings were not statistically significant 
 ( p>0.05 ) , nor were the specificity values obtained in the middle portion in 
 comparison to the coronal and apical thirds ( p>0.05 ) .
mean values and ranges of specificity in each third of the fillings assessed by 
 the examiners ( same letters indicates statistically significant difference at 
 5% )
the intraobserver kappa values were 0.71 for the radiologist and 0.77 for the 
 endodontist .
the present study is the first to investigate the radiographic sensitivity and 
 specificity of laterally condensed root canal fillings . the use of a nylon string to 
 simulate an empty space inside half of the root canals from each group permitted some 
 standardization of the thickness , position and even apical extension of the void through 
 the entire filling , which is a characteristic nearly impossible to control in clinical 
 studies . given that a long radiolucent line is not a usual 
 pattern of laterally condensed root canal filling defects , different results should be 
 expected when a more realistic void simulation method is developed .
the thickness of 0.25 mm for the simulated void was chosen on the basis of prior 
 investigations in which this diameter was considered the threshold to decide whether a 
 root canal obturation was well or poorly condensed .
huybrechts , et 
 al.(2009 ) observed that 
 analogue intraoral radiographs were ineffective for the detection of voids 0.20 mm in 
 diameter . given the large number of simulated defects correctly identified in this 
 study , it could be inferred that the thinnest detectable diameter for filling voids in 
 canine teeth is between 0.20 and 0.25 mm , at least with this imaging technique . because a thin and long radiolucent line is not a usual pattern in radiological images 
 of obturated root canals ,
viewers might have not perceived it as a void despite prior 
 training with defective and non - defective models .
in addition , since the simulated 
 defect was , at most , close to the mesial root canal wall , it is possible that the 
 similarities between the low radiographic densities of control group fillings and dentin 
 at the interface may have smothered the radiolucent void appearance and therefore misled 
 the observers ( background density effect ) .
these circumstances could justify the large number of false 
 negative results and consequently the low sensitivity levels for the radiologist during 
 assessment of the coronal and middle portions of artificial defective fillings . in the radiographic assessment of laterally condensed root canal fillings ,
some false 
 positive results may originate from visualization of multiple voids either inherent to 
 lateral condensation or caused by imperfections in the filling procedure . to estimate this bias ,
a non - radiopaque 
 sealer was used to complete the fillings , and the mean specificity value obtained ( 0.73 ) 
 was comparable to that described by kositbowornchai , et al .
although the 
 examiners of both studies were experienced radiologists , the radiographic 
 superimposition caused by the mineralized maxillary trabeculae ( reproduced in this 
 study ) may have impaired the identification of procedural voids . moreover , in the experimental fillings 
 devoid of simulated defects , the abrupt changes in optical densities between the filling 
 and the dentin may have generated the illusion of lateral radiolucent longitudinal lines 
 that were possibly misdiagnosed as voids by the examiners ( mach band 
 phenomenon ) and , thus , may 
 account for some of the false positive results observed . according to our data ,
the use of both radiopaque sealers caused an equivalent reduction 
 of radiographic sensitivity that was significant in the coronal portion of the fillings 
 and , to a less extent , in the middle third as well ( table 1 ) .
it is possible that the simulated void was hidden by radiographic 
 superimposition resulting from the thicker mass of gutta - percha in addition to sealer 
 accumulation in the wide and 
 oval coronal part of the root canals ; this is an inherent characteristic of the lateral 
 condensation technique . in the apical portion of the fillings ,
the highest sensitivity levels were independent 
 of the sealer applied , a result that corroborate the findings of huybrechts , et 
 al .
the lower 
 gutta - percha and sealer content at this point of the tapered canal as well as the thick 
 diameter of the simulated void may have resulted in easier detection of defects , a 
 phenomenon that may also have contributed to the absence of statistical difference 
 between groups .
the identification of voids in the apical portion of fillings using 
 radiography is important because the apex may harbor bacteria that grow when they 
 receive nutrients from the periapical region or lateral canals , thus compromising the 
 entire treatment . in this study , root canal fillings performed with the sealer of lower radiopacity 
 ( acroseal )
were regarded as having better quality ( high specificity ) 
 compared with fillings performed with the more radiopaque sealer ( ah plus ) 
 . as a potential explanation of this inconsistency ,
this property affects the functional thickness of the 
 sealer and may permit better accumulation between the gutta - percha cones , thus increasing the overall radiopacity 
 of root canal fillings and satisfying 
 examiner expectations regarding filling quality . in this sense , the patterns of sealer 
 distribution through the root canal may depend not only on the physical properties of 
 the sealer , but also on the filling technique applied . in this sense , 
 physical properties other than radiopacity seemed to influence , in a different way , the 
 radiographic perception of defective or adequate root canal fillings performed with 
 lateral condensation .
given that only 
 two commercial root canal sealers were tested in this study , the adoption of other 
 sealers with different physical characteristics could generate stronger evidence about 
 the unique influence of radiopacity on the radiographic detection of root canal filling 
 defects .
the result mentioned above provides evidence that radiopacity levels ranked in 
 vitro are not directly related to quality perceptions of laterally condensed 
 fillings on radiographs .
furthermore , the previous assumption that a more radiopaque 
 sealer might yield a better impression of a compact filling does not appear 
 to have scientific support in these cases .
in addition to the unsuspected radiographic 
 superimposition caused by gutta - percha , the sealer film formed among gutta - percha points 
 may be thinner than that commonly adopted for in vitro tests .
the selection of one radiologist and one endodontist as examiners for this research was 
 based on their radiographic assessment knowledge and on the adoption of the same type of 
 specialists in previous studies .
until now , no dissonance between endodontists and radiologists in the 
 radiographic judgment of root canal fillings has been reported . in the present study , a difference in sensitivity 
 between these specialists was detected in the assessment of control group fillings 
 ( table 1 ) . since only one endodontist was 
 compared to one radiologist , it should be clear that this result is not scientifically 
 or statistically powerful .
we believe that the radiographic view of minor undesirable 
 voids , which were not superimposed by the nonradiopaque sealer , generated uncertainty in 
 the final decision regarding the presence or absence of empty spaces in the fillings . 
 this uncertainty coupled with poor calibration of examiners before the analysis of 
 images allowed their personal experience and subjective knowledge to guide the 
 diagnostic decision , as reported in other investigations .
the perception of filling defects by means of radiographic analysis is important but 
 does not necessarily compromise treatment .
voids can be very short or 
 cul - de - sac in nature , therefore not providing pathways for bacteria 
 and toxins that leak from the root canal third . in this way
, the identification of filling defects per 
 se does not substantiate the need for retreatment , especially when no other 
 signs or clinical symptoms indicate endodontic failure . finally , small filling voids or voids located in buccolingual sites may not be 
 identifiable on periapical radiography .
thus , the results provided in this study suggest 
 that the absence of radiographically identifiable voids in root canal fillings does not 
 ensure they do not exist . for this reason ,
such evidence should not prohibit treatment 
 revision when signs and symptoms of failure are evident .
within the limitations of this ex vivo study , it was concluded that the 
 type of sealer can affect the observers ' ability to detect root canal filling voids 
 during radiographic analysis of upper single - rooted teeth .
in addition , this effect 
 seemed not to be related to the in vitro radiopacity of sealers .
cassia maria fisher rubira and daniela silva who 
 kindly performed the radiographic evaluations and dr jos roberto lauris for 
 statistical advice .
 objectivethis study compared the influence of three epoxy resin - based sealers with distinct 
 radiopacities on the observers ' ability to detect root canal filling voids during 
 radiographic analysis . 
 material and methodsthe root canals of 48 extracted maxillary canines were prepared and divided into 
 three groups . 
 each group was laterally condensed with one sealer ( ah 
 plustm , acroseal or a non - radiopaque sealer ) , and a 
 longitudinal void was simulated in half of the specimens from each group ( n=8 ) . 
 
 buccolingual radiographs were obtained and randomly interpreted for voids by a 
 radiologist and an endodontist in a blinded fashion . 
 teeth were cut and inspected 
 under a microscope to confirm the position of void . 
 differences in sensitivity and 
 specificity between groups and examiners were compared using the fisher 's exact 
 and mcnemar tests , respectively ( =0.05).resultssignificantly lower sensitivity levels ( p<0.05 ) were observed in the coronal 
 portion of fillings performed with both radiopaque sealers . 
 specificity values for 
 acroseal were significantly higher ( p<0.05 ) in the coronal and 
 apical portions of fillings.conclusionsthe type of root canal sealer can affect the observers ' ability to detect root 
 canal filling voids during radiographic analysis of upper single - rooted teeth . 
INTRODUCTION
MATERIAL AND METHODS
Tooth preparation
Radiographic procedure
Image evaluation
Statistical analysis
RESULTS
Sensitivity
Specificity
Intraobserver agreement
DISCUSSION
CONCLUSIONS
ACKNOWLEDGEMENTS