it has been described as a protection against bacteriological diffusion and penetration into the dentinal tubules8,10 .
other authors9,12 consider that the presence of smear layer may prevent the endodontic filling material from penetrating into dentinal tubules and compromise its adhesion to the canal walls .
the importance of smear layer removal in achieving better root canal seal has been extensively investigated .
vivacqua - gomes , et al.17 ( 2002 ) observed the influence of irrigants on the coronal microleakage of laterally condensed gutta - percha root fillings , and the best results occurred when 1% naocl and 17% edta were used . on the other hand ,
madison and krell5 ( 1984 ) compared the effects of smear layer removal on the apical sealing of endodontically treated teeth and found no statistically significant differences between the groups irrigated with redta and naocl .
furthermore , saleh , et al.12 ( 2008 ) observed that the removal of smear layer did not prevent bacterial penetration along the root canal fillings .
clearly , few studies correlate accessory canal filling to the presence or absence of smear layer .
goldberg , et al.3 ( 1986 ) evaluated in vitro the effects of different solutions ( 15% edta , 5% naocl and distilled water  control ) used for root canal irrigation on the filling of lateral canals and observed that more lateral canals could be filled when 15% edta was used , with statistically significant difference when this group was compared to the other two . with the purpose of evaluating the filling of accessory canals after different final irrigation regimens ,
villegas , et al.16 ( 2002 ) examined cleared teeth obturated with either system b or obtura ii .
the results showed no differences between the use of 6% naocl alone and a 15% edta/6% naocl combination .
more recently , bertacci , et al.2 ( 2007 ) compared different solutions used for irrigation regarding their influence on root canal system filling .
there were no statistically significant differences regarding number , length and diameter of filled ramifications .
the smear layer did not prevent the sealing of lateral canals . considering the lack of studies discussing this subject , the aim of this study was to evaluate in vitro the influence of smear layer removal on the filling of lateral canals , secondary canals and apical deltas in teeth prepared either using or not edta as a final irrigant and filled with lateral condensation of gutta - percha and an epoxy resin root canal sealer ( ah plus ) .
teeth with apical curvatures , resorption , more than one root or canal , and previous endodontically treated teeth were discarded .
the teeth were immersed in 1% naocl for 12 h to eliminate root - adhered organic debris and calculi , immediately washed in running water , dried with absorbent paper and stored in glass vials numbered 1 to 80 containing saline . before canal shaping , the teeth were decoronated at the cementoenamel junction to eliminate possible variations during the surgical phase of canal access and instrumentation . after this
, the teeth were randomly assigned to two groups of 40 roots each , according to the irrigation regimen used : group i was irrigated with 1% naocl and group ii was irrigated with 1% naocl followed by irrigation with 17% edta .
the solutions used for irrigation ( 1% naocl and 17% edta ) were delivered from 1.8 ml sterile plastic tubes in order to standardize the solution volume used in each root canal .
the root canals were emptied and explored using k- files # 10 ( maillefer instruments s.a , ballaigues , switzerland ) . for canal
the working length was established 1 mm short of the point at which a # 10 k- file exited the apical foramen , in order to obtain an apical stop .
the step - back technique was used for root canal shaping . the thinnest file that would shorten the canal walls to the previously determined extent
the file for recapitulation was standardized using a # 30 k - flexofile file and the final file was a # 55 k - file . during instrumentation , in both groups , the canals were copiously irrigated with 1% naocl . in group ii , after shaping , the canals were also irrigated with 17% edta , followed by a final flush with naocl . after irrigation , the canals of both groups were dried using paper points 15 - 40 ( dentisply ind
ltda , petrpolis , rj , brazil ) and finally obturated with lateral condensation of gutta - percha and ah plus sealer ( dentsply / detrey , konstanz , germany ) beyond the apical stop . for each canal , a standardized gutta - percha cone ( dentisply ind
ltda ) was selected according to the root canal length and diameter , preventing passage of the accessory gutta - percha points .
the sealer was introduced into the root canals with a # 30 k - flexofile file , and the standardized gutta - percha cone coated with sealer was fitted as a master cone .
lateral compaction was performed with # 25 and # 30 finger spreaders ( dyna , bourges , france ) , and b7 and b8 accessory cones ( tanari , manacapuru , am , brazil ) were introduced to fill the root canal .
excess gutta - percha was removed with a heated instrument and cold pluggers were used to vertically condense the coronal gutta - percha .
clearing was proposed by robertson , et al.11 ( 1980 ) to allow a three - dimensional visualization of the internal tooth structure .
the specimens were then dehydrated in 80 ethanol for 12 h , followed by 1 h in 90 ethanol and 1 h in 96 ethanol .
the specimens were then allowed to dry naturally for 10 min and were put into glass vials with methyl salicylate ( c8h8o3 ) .
lateral canals , secondary canals and apical deltas were observed under a stereomicroscope at 40x magnification ( meiji techno co. , ltd . ,
the microscopic analysis identified the presence as well as the type of canal ramifications in both groups of teeth and allowed for their classification .
the outcomes of the influence of smear layer removal on the obturation of root canal ramifications were evaluated with a two- proportion binomial test in order to compare two irrigation regimes ( with and without edta ) .
the sample consists of 80 teeth , divided into 2 groups of 40 teeth each .
group i was irrigated with 1% naocl and group ii with 1% naocl followed by a final irrigation with 17% edta . 

table 1 presents ramifications observed in the groups , showing that smear layer removal does not interfere on the root canal ramifications obturation . in group
i ( no edta ) , 5 apical deltas were found ( figure 1a ) , while in group ii ( treated with edta ) , 3 apical deltas could be visualized . as to secondary canals ,
7 ramifications were found in group i and 8 in group ii ( figure 1b ) . on the other hand , when lateral canals were analyzed ,
figure 2 shows the number of ramifications and their percentiles for groups i and ii . in group
i , 45% of the teeth had at least one filled ramification ( 18 teeth ) .
in group ii the occurrence of filled root canal ramifications was 37.5% of the sample ( 15 teeth ) . according to the chi - square test
, there were no statistically significant differences in the obturation of root canal ramifications between groups i and ii ( p = 0.32 ) .
it has been widely used for smear layer removal and is the most frequently used substance in studies that compare smear - covered and smear - free surfaces in achieving good root canal seal6,7,15 .
white , et al . 18 ( 1984 ) observed more effective results for smear layer removal when edta was used as a final irrigant .
vivacqua - gomes , et al.17 ( 2002 ) observed lower infiltration as well as better apical seal for teeth irrigated with edta .
those findings support the advantages of removing the smear layer and indicate that edta is an efficient substance for this purpose .
however , in the present study , the use of 17% edta and naocl as final irrigants after root canal shaping did not affect root canal ramification filling .
the obturation of root canal ramifications can establish a connection between the main root canal and the periodontal ligament , as well as the apical foramen .
therefore , periodontal problems might be associated with necrotic and infected root canal ramifications , highlighting the importance of the capacity of the endodontic sealer to flow into these irregularities1 .
although a complete seal can not be achieved1,14 , the physical presence of the sealer and its antimicrobial property might eliminate or inhibit the growth of microorganisms in the root canal system13 . according to data available in the literature
, one may infer that smear layer removal from the root canal walls is effective , clearing the entrance of the dentinal tubules and canal ramifications . however , edta did not act upon the depth of the dentinal material .
in addition , a perfect adaptation could be observed between the cement and the filling material in the inner diameter space of the root canal in those specimens where edta was applied .
no statistically significant difference was found in the filling of ramifications between groups i and ii . our findings agree with those of villegas , et al.16 ( 2002 ) and bertacci , et al.2 ( 2007 )
. their results did not show differences between the filling of root canal ramifications in teeth irrigated or not with edta . in those studies
, the canals were obturated using warm gutta - percha obturation systems , while the present study used the lateral condensation technique .
it may be inferred that , despite the obturation technique used , lateral canals and apical deltas can be obturated without using decalcification solutions . on the other hand ,
however , those authors used radiographic images instead of clearing of the specimens and , according to almeida , et al.1 ( 2007 ) , the radiographic analysis can fail to demonstrate filled lateral and accessory canals .
smear layer removal may be important in achieving better apical seal as well as providing a better adjustment of the filling material to the dentin walls .
however , based on the results of the present study , we can not assign to edta the capacity to increase the number of ramifications filled during root canal obturation .
another issue that deserves attention is the high percentage of obturated ramifications shown in the present study .
given that a total of 33 ramifications with filling material could be observed ( 41.2% of the sample ) , two points should be highlighted : ( 1 ) the high prevalence of such ramifications in the root canal system ; and ( 2 ) the possibility of obturating these ramifications using simple techniques that are readily available to the general dentist , such as guttapercha lateral condensation , provided that certain principles of endodontic treatment are observed , although gutta - percha thermoplastic techniques are more efficient in filling lateral canals ( goldberg , et al.4 2001 ) .
it was also seen that the internal morphology of the canines used in this study presented a larger number of secondary canals when compared to lateral canals and apical deltas . moreover , if one were to add apical deltas to secondary canals as observed in the sample , it could be verified that the apical third is the section that presents the largest number of ramifications .
given that the apical third is the most technically challenging region of the root canal , it is mandatory to proceed with careful instrumentation using abundant irrigation and use of intracanal medication that will act on the areas that are not accessible to instrumentation .
according to the present study , the use of edta as a final irrigant after root canal shaping does not optimize the filling of lateral canals , secondary canals and apical deltas when gutta - percha lateral condensation was the technique employed for root canal filling .
there were no significant differences regarding the filling of canal ramifications when comparing irrigation with 1% naocl and irrigation with 1% naocl followed by irrigation with 17% edta and a final flush with naocl .
 objective : this study evaluated whether smear layer removal has any influence on the filling of the root canal system , by examining the obturation of lateral canals , secondary canals and apical deltas.material and methods : eighty maxillary and mandibular canines were randomly divided into two groups , according to their irrigation regimen . both groups were irrigated with 1% naocl during canal shaping , but only the teeth in group ii received a final irrigation with 17% edta for smear layer removal . 
 the root canals were obturated with lateral condensation of gutta - percha and the specimens were cleared , allowing for observation under the microscope.results:in groups i and ii , 42.5% and 37.5% of the teeth , respectively , presented at least one filled canal ramification . 
 although a larger number of obturated ramifications was found in group i , there were no statistically significant differences between the two groups ( p = 0.4957).conclusion : smear layer removal under the conditions tested in this study did not affect the obturation of root canal ramifications when lateral condensation of gutta - percha was the technique used for root canal filling . 
INTRODUCTION
MATERIAL AND METHODS
RESULTS
DISCUSSION
CONCLUSIONS