it is generally accepted that microleakage between the filling materials and root canal 
 walls might adversely affect the outcome of root canal treatment . therefore , it is critical the complete 
 sealing of the root canal system after cleaning and shaping in order to avoid the 
 bacterial penetration and re - infection of the root and periapical tissues . the association of gutta - percha cones 
 and root canal sealer has been traditionally used for this purpose . however , in the last 
 decade , the dentin adhesive technology has been incorporated into the root canal filling 
 techniques to reduce apical and coronal leakage by bonding to root canal walls . etch - and - rinse adhesives have been 
 tested with resin cements and the 
 combination of a dentin - bonding agent and an epoxy resin - based root canal sealer 
 significantly reduced apical leakage . in restorative dentistry , the self - etch adhesive systems have shown less technique 
 sensitivity , with reliable long - term performance of a two - step mild self - etch 
 adhesive . following this trend , pentron clinical technologies 
 ( wallingford , ct , usa ) has developed the epiphany system , which contains a self - etch 
 primer , a dual - cured composite resin sealer and a polyester - based thermoplastic 
 root - filling material ( resilon ; resilon research llc , madison , ct , usa ) . 
 according to shipper , et al . ( 2004 ) 
 this material has been shown to be more resistant to bacterial leakage than epoxy 
 resin - based sealers for filling root canals . in endodontics , the controversy about the performance of adhesive systems inside the 
 root canal remains . despite that , 
 other possibility is combining epiphany primer with ah plus in an attempt to add the 
 hybridization capacity to the gold standard endodontic sealer . the reason for this is 
 that the removal of the smear layer with ethylenediamine tetraacetic acid ( edta ) does 
 not provide the same etching pattern usually associated with the hybrid layer , which is 
 considered an important factor for dentin bonding . the majority of studies have evaluated apical or coronal microleakage , and few have 
 focused gap formation at the dentin / sealer interface . so far , no correlation between microleakage and gap 
 formation has been established in the literature . thus , it is reasonable to believe that 
 the association of both methods would provide a more precise evaluation of the adhesive 
 interface . the aim of this study was to compare the apical sealing and gap formation of ah 
 plus / gutta - percha with epiphany system . in addition , the opportunity was taken to assess 
 the effect of the association of epiphany primer and ah plus / gutta - percha on apical 
 sealing and gap formation . the null hypotheses tested were as follows : ( 1 ) there is no 
 difference in apical microleakage or ( 2 ) apical gap formation among the experimental 
 groups and ( 3 ) there is no correspondence between apical microleakage and the presence 
 of gaps . thirty - nine lower single - rooted human premolars with straight root canals and fully 
 developed apices ( local ethics committee approval 177/05 ) were cleaned and submitted 
 to 18.5 kgy gamacell radiation ( nuclear energy research institute , so paulo , 
 sp , brazil ) , and stored in saline solution at 4c . after endodontic access , 
 the real working length ( rwl ) was established 1 mm short of the apical foramen . a 
 crown - down technique was used ( up to k - file # 50 ) under constant irrigation with 0.5% 
 naocl . the smear layer was removed with 17% edta ( 5 ml ) and 0.5% naocl ( 5 
 ml ) followed by saline 
 solution ( 15 ml ) . three coats of nail polish were applied to 
 external root surfaces except for the apical 2 mm . the teeth were randomly ( http://www.random.org ) divided into 
 3 experimental groups ( n=11 ) . the endodontic sealers were 
 prepared according to the manufacturer 's instructions and the cold lateral 
 condensation filling technique ( lc ) was used according with the following 
 description : an iso # 50 master gutta - percha cone was lightly coated with ah plus sealer ( ah 
 plus ; dentsply detrey , konstanz , germany ) and placed into the 
 canal to rwl . a size b finger spreader ( dentsply maillefer , ballaigues , switzerland ) 
 was then inserted into the canal to a level approximately 1 mm short of rwl . lc with 
 accessory gutta - percha cones was performed until the entirely filled root canal . the 
 excess gutta - percha was removed with a heated plugger and then compacted 
 vertically . adhesive - modified technique was used for bonding ah plus to intraradicular dentin . a 
 paper point soaked with epiphany primer was used to etch dentin ( 30 s ) and the excess 
 was removed with paper points . the coronal surface of the root filling was 
 light - cured for 40 s ( 600 mw / cm ) . the positive controls ( n=3 ) were left unfilled and coated as described earlier . the 
 negative controls ( n=3 ) were filled and totally coated , including the apical 
 foramina . the openings were sealed ( cavit w , 3 m espe , st paul , mn , usa ) , and 
 stored in a chamber held at 100% humidity and 37c for 7 days . next , all teeth 
 were immersed in a 50-wt% aqueous silver nitrate solution ( agno3 , ph7.0 ) 
 in the darkness that was buffered using naoh 0.1 n for 24 h at 37c . the silver - impregnated teeth 
 were rinsed and placed in photodeveloper ( 8 h ) in fluorescence light to reduce the 
 silver ions into metallic silver . lake bluff , 
 il , usa ) , longitudinally sectioned in an isomet 1000 precision saw ( buehler ) at low 
 speed ( 200 rpm ) with a water - cooled diamond blade . the interfaces were etched with a 
 35% phosphoric acid solution ( 5 s ) , rinsed with distilled water ( 30 s ) and gently 
 air - dried . then , specimen preparation followed the protocol 1 for apical microleakage 
 analysis using scanning electron microscopy / energy dispersive spectroscopy ( sem / eds ) ; 
 or the protocol 2 for gaps analysis using sem according to the following 
 description : specimens were fixed , dehydrated in ascending grades of ethanol and final chemical 
 drying in hmds ( hexamethyldisilazane , sigma - aldrich inc . , louis , mo , usa ) for 10 
 min , and covered with 
 carbon ( sputter coater scd 050 , bal - tec ag , balzers , liechtenstein ) . the apical 5 mm 
 of the root canal filling were divided into 5 regions of 1 mm to evaluate 
 microleakage by sem leo stereoscan 440 ( leo electron microscopy ltd . , cambridge , 
 england ) using back scattered electrons ( bse ) mode ( figure 1a ) . the eds ( inca software , oxford , uk , england ) was performed in 
 lower magnification within a pre - determined area ( 300 m ) ( figure 1b ) , and in a higher magnification , the 
 identification of silver was made punctually to determine its exact location ( figure 1c ) . each 1 mm region was classified 
 according to the following scores : 0 ( absence of leakage in both interfaces ) and 1 
 ( presence of leakage in at least one of the interfaces ) . in figures 1d and 1e scanning electron microscopy ( sem ) micrographs using back scattered electrons 
 ( bse ) mode and corresponding energy dispersive spectroscopy ( eds ) spectrum of 
 agno3 leakage : ( a ) - the apical 5 mm of the root canal filling 
 divided into 1 mm - regions . pointer at the detected metallic silver ; ( b )  area 
 ( 300 m ) scanned for the existence of silver and 
 respective eds spectrum ( arrow ) and ( c ) - in detail , punctual eds confirmation 
 of its exact location . gp = gutta - percha ; d = dentin impressions of polyvinyl siloxane ( aquasil , ulv , dentsply detrey ) were 
 made of the interfaces and the surfaces replicated with epoxy resin 
 ( epon - thin , buhler ) . the replicas were covered with carbon to 
 investigate the presence of gaps at the dentin / sealer and sealer / cone interfaces , as 
 described previously , using secondary electrons ( se ) mode . as the gaps were not 
 continuous , for each 1 mm - region , two interfaces were analyzed ( figure 2a ) and classified as : type 0 : both interfaces were 
 gap - free , type 1 : gap at dentin / sealer interface ( figure 2b ) , type 2 : gap at sealer / cone interface ( figure 2c ) , and type 3 : both types of gaps present . therefore , 
 for each experimental group , 11 replicas were prepared ; 55 regions were evaluated and 
 accordingly classified . scanning electron microscopy ( sem ) micrographs using secondary electrons ( se ) 
 and back scattered electrons ( bse ) mode of the replica and the section of the 
 same specimen , respectively . ( a ) - the apical 5 mm of the root canal filling 
 divided into 1 mmregions . classification of the types of gaps : ( b )  type 1 : 
 gap between dentin / sealer ( pointer ) ; air voids were present within the sealer 
 ( open arrow ) ; ( b ' ) - silver penetration was evident along the dentin / sealer 
 interface , into dentinal tubules in a reticular form and granular aspect on the 
 dentin surface ( arrowhead ) ; ( c )  type 2 : gap between sealer / cone ( pointer ) - 
 cohesive fracture of the sealer ( open arrow ) ; ( c ' ) - the area marked in figure 
 c at higher magnification : silver deposition into the dentinal tubules in a 
 reticular form and granular aspect within the sealer layer ( arrowhead ) could be 
 seen ; ( the sealer thickness was indicated between black / white arrowheads . gp = gutta - percha ; d = dentin ; r = resilon ) the data obtained for apical microleakage and types of gaps were statistically 
 analyzed ( =0.05 ) using the ordinal logistic regression model and correspondence analysis in the minitab statistical software 
 program ( minitab inc . the counting of regions analyzed for gaps was also computed and adjusted in a 
 generalized linear model with poisson distribution and logarithmic link function . the 
 sealers groups ( ah plus , ah primer and epiphany ) and the type of gap were considered 
 as explanatory variables and ah plus and the type 0 as references . thirty - nine lower single - rooted human premolars with straight root canals and fully 
 developed apices ( local ethics committee approval 177/05 ) were cleaned and submitted 
 to 18.5 kgy gamacell radiation ( nuclear energy research institute , so paulo , 
 sp , brazil ) , and stored in saline solution at 4c . after endodontic access , 
 the real working length ( rwl ) was established 1 mm short of the apical foramen . a 
 crown - down technique was used ( up to k - file # 50 ) under constant irrigation with 0.5% 
 naocl . the smear layer was removed with 17% edta ( 5 ml ) and 0.5% naocl ( 5 
 ml ) followed by saline 
 solution ( 15 ml ) . three coats of nail polish were applied to 
 external root surfaces except for the apical 2 mm . the teeth were randomly ( http://www.random.org ) divided into 
 3 experimental groups ( n=11 ) . the endodontic sealers were 
 prepared according to the manufacturer 's instructions and the cold lateral 
 condensation filling technique ( lc ) was used according with the following 
 description : an iso # 50 master gutta - percha cone was lightly coated with ah plus sealer ( ah 
 plus ; dentsply detrey , konstanz , germany ) and placed into the 
 canal to rwl . a size b finger spreader ( dentsply maillefer , ballaigues , switzerland ) 
 was then inserted into the canal to a level approximately 1 mm short of rwl . lc with 
 accessory gutta - percha cones was performed until the entirely filled root canal . the 
 excess gutta - percha was removed with a heated plugger and then compacted 
 vertically . adhesive - modified technique was used for bonding ah plus to intraradicular dentin . a 
 paper point soaked with epiphany primer was used to etch dentin ( 30 s ) and the excess 
 was removed with paper points . the coronal surface of the root filling was 
 light - cured for 40 s ( 600 mw / cm ) . the positive controls ( n=3 ) were left unfilled and coated as described earlier . the 
 negative controls ( n=3 ) were filled and totally coated , including the apical 
 foramina . the openings were sealed ( cavit w , 3 m espe , st paul , mn , usa ) , and 
 stored in a chamber held at 100% humidity and 37c for 7 days . next , all teeth 
 were immersed in a 50-wt% aqueous silver nitrate solution ( agno3 , ph7.0 ) 
 in the darkness that was buffered using naoh 0.1 n for 24 h at 37c . the silver - impregnated teeth 
 were rinsed and placed in photodeveloper ( 8 h ) in fluorescence light to reduce the 
 silver ions into metallic silver . lake bluff , 
 il , usa ) , longitudinally sectioned in an isomet 1000 precision saw ( buehler ) at low 
 speed ( 200 rpm ) with a water - cooled diamond blade . the interfaces were etched with a 
 35% phosphoric acid solution ( 5 s ) , rinsed with distilled water ( 30 s ) and gently 
 air - dried . then , specimen preparation followed the protocol 1 for apical microleakage 
 analysis using scanning electron microscopy / energy dispersive spectroscopy ( sem / eds ) ; 
 or the protocol 2 for gaps analysis using sem according to the following 
 description : specimens were fixed , dehydrated in ascending grades of ethanol and final chemical 
 drying in hmds ( hexamethyldisilazane , sigma - aldrich inc . , st . louis , mo , usa ) for 10 
 min , and covered with 
 carbon ( sputter coater scd 050 , bal - tec ag , balzers , liechtenstein ) . the apical 5 mm 
 of the root canal filling were divided into 5 regions of 1 mm to evaluate 
 microleakage by sem leo stereoscan 440 ( leo electron microscopy ltd . , cambridge , 
 england ) using back scattered electrons ( bse ) mode ( figure 1a ) . the eds ( inca software , oxford , uk , england ) was performed in 
 lower magnification within a pre - determined area ( 300 m ) ( figure 1b ) , and in a higher magnification , the 
 identification of silver was made punctually to determine its exact location ( figure 1c ) . each 1 mm region was classified 
 according to the following scores : 0 ( absence of leakage in both interfaces ) and 1 
 ( presence of leakage in at least one of the interfaces ) . in figures 1d and 1e scanning electron microscopy ( sem ) micrographs using back scattered electrons 
 ( bse ) mode and corresponding energy dispersive spectroscopy ( eds ) spectrum of 
 agno3 leakage : ( a ) - the apical 5 mm of the root canal filling 
 divided into 1 mm - regions . pointer at the detected metallic silver ; ( b )  area 
 ( 300 m ) scanned for the existence of silver and 
 respective eds spectrum ( arrow ) and ( c ) - in detail , punctual eds confirmation 
 of its exact location . impressions of polyvinyl siloxane ( aquasil , ulv , dentsply detrey ) were 
 made of the interfaces and the surfaces replicated with epoxy resin 
 ( epon - thin , buhler ) . the replicas were covered with carbon to 
 investigate the presence of gaps at the dentin / sealer and sealer / cone interfaces , as 
 described previously , using secondary electrons ( se ) mode . as the gaps were not 
 continuous , for each 1 mm - region , two interfaces were analyzed ( figure 2a ) and classified as : type 0 : both interfaces were 
 gap - free , type 1 : gap at dentin / sealer interface ( figure 2b ) , type 2 : gap at sealer / cone interface ( figure 2c ) , and type 3 : both types of gaps present . therefore , 
 for each experimental group , 11 replicas were prepared ; 55 regions were evaluated and 
 accordingly classified . scanning electron microscopy ( sem ) micrographs using secondary electrons ( se ) 
 and back scattered electrons ( bse ) mode of the replica and the section of the 
 same specimen , respectively . ( a ) - the apical 5 mm of the root canal filling 
 divided into 1 mmregions . classification of the types of gaps : ( b )  type 1 : 
 gap between dentin / sealer ( pointer ) ; air voids were present within the sealer 
 ( open arrow ) ; ( b ' ) - silver penetration was evident along the dentin / sealer 
 interface , into dentinal tubules in a reticular form and granular aspect on the 
 dentin surface ( arrowhead ) ; ( c )  type 2 : gap between sealer / cone ( pointer ) - 
 cohesive fracture of the sealer ( open arrow ) ; ( c ' ) - the area marked in figure 
 c at higher magnification : silver deposition into the dentinal tubules in a 
 reticular form and granular aspect within the sealer layer ( arrowhead ) could be 
 seen ; ( the sealer thickness was indicated between black / white arrowheads . gp = gutta - percha ; d = dentin ; r = resilon ) the data obtained for apical microleakage and types of gaps were statistically 
 analyzed ( =0.05 ) using the ordinal logistic regression model and correspondence analysis in the minitab statistical software 
 program ( minitab inc . the counting of regions analyzed for gaps was also computed and adjusted in a 
 generalized linear model with poisson distribution and logarithmic link function . the 
 sealers groups ( ah plus , ah primer and epiphany ) and the type of gap were considered 
 as explanatory variables and ah plus and the type 0 as references . the ordinal logistic regression analysis demonstrated that there was no statistically 
 significant difference ( p>0.05 ) among the groups tested and types of gaps over 
 the logit of microleakage . the model was adjusted to identify the 
 effect of the type of gap on microleakage . the type 3 data were not considered isolated 
 in the analysis ( very few regions ) but joined with type 2 data ( figure 2c ; table 1 ) . the 
 adjustment tests of the model presented high p - values for pearson 's test ( p=0.900 ) and 
 deviance ( p=0.852 ) . the adjusted model demonstrated that the effect of the type of gap 
 on the logit of microleakage is significant when compared to the 
 presence of types 1 and 2 ( figure 2b and 2c , respectively ) of gap with the absence of gap 
 ( p=0.047 ) . the correspondence analysis also showed the association between microleakage 
 and both types of apical gaps ( figure 3 ) . correspondence analysis of microleakage vs. type of gap : ( inf.0 ) - absence of 
 leakage ; ( inf.1 ) - leakage up to the 1 millimeter ; ( inf.2 ) leakage 
 up to the 2 mm ; ( inf.3 )  leakage up to the 3 
 millimeter ; ( inf.5 )  leakage up to the 5 millimeter ; ( f.0 )  absence 
 of gaps ; ( f.1 )  gaps type 1 ; ( f.2 ) - gaps types 1 and 2 . the absence of leakage 
 is associated with the absence of gap ; leakage up to the 1 millimeter 
 is associated with type 1 ; and more extensive leakage is associated with types 1 
 and 2 frequency and type of gaps in the apical 5 mm of root canal fillings percentage of regions with gaps . type 0 : absence of gaps ; type 1 : gaps between 
 dentin and sealer ; type 2 gaps between sealer and cone the generalized linear model with poisson distribution ( table 1 ) found no difference between ah plus and ah primer ( p=0.497 ) in 
 distribution of each type of gap , but they presented more type 0 regions 
 ( p<0.001 ) . there was a significant interaction between epiphany and the type of 
 gap ( p<0.003 ) and for this group , there were more type 1 regions . based on the findings of this study , the first null hypothesis could not be rejected . recently some studies have shown similar results between ah plus and epiphany on apical 
 sealing ability using the fluid filtration method . consistent with these 
 studies , our results indicate that the epiphany system is as effective as ah 
 plus / gutta - percha in preventing microleakage based on the chemical tracer penetration 
 analysis by sem and the use of epiphany primer does not reduce the microleakage of ah 
 plus . nevertheless , other researches pointed out that the epiphany system provided the 
 greatest resistance to the movement of fluids or dye leakage 
 test , when compared to epoxy 
 resin - based root canal sealers , but others have just indicated the opposite . these apparent discrepancies can perhaps be explained by the 
 methodology used and their variables . these results agree with those of previous studies in which , microleakage markers were 
 used to evaluate apical sealing of the same endodontic sealers . the tracer 
 selected was agno3 , which may penetrate into dentinal tubules due to their 
 physical and chemical characteristics including : concentration , smaller molecular size , 
 its neutral ph , diffusion coefficient and service life up to 168 h post - preparation time of 
 solution . another reason for 
 this choice is that metallic silver deposits may be observed by sem using back scattered 
 electrons ( bse ) mode . on the other hand , the results of the current study disagree with the findings of 
 shipper , et al . an 
 explanation for this would be that their studies have evaluated coronal and not apical 
 bacterial leakage . indeed , coronal seal might be favorably influenced by photoactivation 
 of the material which is unlikely to occur in the apical third . furthermore , it is speculated that in in 
 vivo studies ( dogs ) , the high release of calcium hydroxide ( 41.46 mg / l ) that 
 would occur during the process of epiphany sealer solubilization , would make the medium 
 alkaline , resulting in acceleration of the periapical tissue repair process . this study has shown that the presence of apical gaps at the sealer / dentin or 
 sealer / cone interfaces had an effect on apical microleakage . the epiphany group 
 presented more type 1 gaps than the other groups ( table 
 1 ) , rejecting the second null hypothesis . these results corroborate with 
 previous observation of gaps in the apical 4 mm of epiphany or ah plus - filled root 
 canals . stress generated 
 during the polymerization shrinkage of epiphany sealer has probably influenced the 
 integrity loss at the sealer / dentin interface . in addition , the cavity configuration factor ( c - factor ) is 
 highly unfavorable for adhesion inside root canals . moreover , it is known that analysis of gap formation of 
 vertically sectioned root filled teeth hides the risk of artifacts during sectioning . therefore , in this study , the sections were made at low speed under water cooling . the 
 resin - epoxy replicas at the dentin / sealer and sealer / cone interfaces were made before 
 the specimens had been prepared for sem examination in order to differentiate genuine 
 gaps from artifactual gaps created after vacuum desiccation in conventional scanning 
 electron microscopes . few studies have focused on apical sealing from two separate perspectives , such as 
 microleakage and apical gap formation . sem was used to evaluate these perspectives , but it was restricted to a descriptive 
 approach . a systematization of the observations , complemented by a statistical analysis , such as 
 the one performed in this study , could provide greater methodological accuracy and 
 impartiality for comparing the experimental groups . the correspondence of analysis 
 between the types of gaps and linear extent of agno3 leakage ( fig . 3 ) confirms the effect of gaps on apical 
 microleakage , expressed by the silver deposition into gaps that extended deeply inside 
 dentinal tubules ( fig . regarding to statistical analysis , the ordinal logistic regression analysis model was 
 used due to microleakage was considered categorized ordinal response variable ( ranging 
 from 0 - no leakage to 5 - leakage up to the fifth millimeter ) . the correspondence 
 analysis is a method that leads to visualize the association between two categorical 
 variables , in this case microleakage and the type of gap . the generalized linear model 
 with poisson which is an extension of usual regression model was performed to quantify 
 the distribution of types of gaps . this result could be explained by two hypotheses : ( 1 ) 
 the low degree of conversion of the epiphany sealer and ( 2 ) the formation of hydrogel at the bond interface resulting 
 from the incomplete evaporation of the epiphany primer solvent . the second hypothesis could also explain the inefficacy 
 of epiphany primer in improving the sealing capacity of ah plus . moreover , there is a 
 chemical incompatibility between these two materials , since the epoxy resin sealers do 
 not copolymerize with methacrylate resin - based adhesives . other studies should be carried out to clarify the 
 sealing ability of the root - filled materials studied . it may be concluded that none of the tested materials completely sealed the apical 5 mm . the presence 
 of gaps had an effect on apical microleakage for all materials . comparing the materials , 
 epiphany system presented more regions containing gaps between the dentin and the sealer 
 ( type 1 ) . in view of these findings , clinically , it can be suggested that ah plus would 
 provide a better apical seal . this study was partially supported by capes ( coordenao de 
 aperfeioamento de pessoal de nvel superior)/institutional 
 qualification program ( pqi n : 0090/03 - 4 ) .
objectivethe aim of this study was to compare the correspondence between gap formation and 
 apical microleakage in root canals filled with epoxy resin - based ( ah plus ) 
 combined or not with resinous primer or with a dimethacrylate - based root canal 
 sealer ( epiphany ) . 
 material and methodsthirty - nine lower single - rooted human premolars were filled by the lateral 
 condensation technique ( lc ) and immersed in a 50-wt% aqueous silver nitrate 
 solution at 37c ( 24 h ) . 
 after longitudinal sectioning , epoxy resin 
 replicas were made from the tooth specimens . 
 both the replicas and the specimens 
 were prepared for scanning electron microscopy ( sem ) . 
 the gaps were observed in 
 the replicas . 
 apical microleakage was detected in the specimens by sem / energy 
 dispersive spectroscopy ( sem / eds ) . 
 the data were analyzed statistically using an 
 ordinal logistic regression model and analysis of correspondence ( =0.05 ) . 
 resultsepiphany presented more regions containing gaps between dentin and sealer 
 ( p<0.05 ) . 
 there was correspondence between the presence of gaps and 
 microleakage ( p<0.05 ) . 
 microleakage was similar among the root - filling 
 materials ( p>0.05 ) . 
 conclusionsthe resinous primer did not improve the sealing ability of ah plus sealer and the 
 presence of gaps had an effect on apical microleakage for all materials .