one of goals of root canal obturation is to obtain hermetic sealing of the root canal system , favoring the process of apical and periapical repair after endodontic therapy .
inadequate filling can result in fluid movements into the filling defects , inducing a periapical chronic inflammatory reaction and compromising the treatment success .
other factors lead to failures sometimes not resolvable through the intracanal therapy , such as drilling accidents and root resorptions .
therefore , in some situations , surgical complementation is necessary in order to obtain apical repair .
therefore , several surgical techniques were proposed , including them apicoectomy followed by retrograde filling .
many materials have been proposed for utilization in retrograde fillings as amalgam2,4,11,12,16,17,20,21,23 , calcium hydroxide based cements5,13,14 , zinc oxide and eugenol2,4,13,14,17,21,22,23,27 , mineral trioxide aggregate 1,2,4,7,10,11 , 12,13,14,20,21,22,23,25 , resins13 , and portland cement7,11 .
this new proliferation of materials raised doubts about their use , mainly because until now an ideal material that presents adequate physical - chemical and biological properties , such as easy manipulation , dimensional stability , non toxicity , radiopacity , non resorbability , not being affected by the presence of humidity and able to stimulate the repair of apical tissue3 , has not been achieved in the literature .
the mineral trioxide aggregate ( mta ) has been shown to be better than other retrograde filling materials with regard to citotoxicity14 , sealing25 , marginal adaptation22 and induction of periodontal ligament repair12 .
besides , portland cement has been shown to have similar biological properties compared with mta and calcium hydroxide10 . the objective of this study was to evaluate the apical leakage of root - end preparations filled with portland cement ( concrebrs s / a , montes claros , mg , brazil ) , sealapex ( kerr corporation , orange , california , usa ) with addition of zinc oxide ( odahcam  herpo produtos dentrios ltda , rio de janeiro , rj , brazil ) and mineral trioxide aggregate proroot mta ( dentsply international , johnson city , tn , usa ) .
in this study , forty - two single - rooted human teeth extracted for several reasons and selected according to their external and internal anatomy were used . the teeth were maintained in 10% formalin solution for 24 hours and transferred to saline solution at the time of use .
them , they were cleaned and their crowns cut off close to the cementoenamel junction with a carborundum disc at low speed under water coolant . a k - file # 10 ( maillefer - swiss company )
was inserted into the root canal to locate and unblock the apical foramen . each root canal
was cleaned with 1% naocl and shaped to a # 60 k - file at the working length , using the step - back technique .
then , the root canals were dried with absorbent points ( tanari- ltda- brazil ) and obturated with gutta - percha ( tanari- ltda- brazil ) and sealapex ( kerr corporation - usa ) root canal sealer using lateral condensation technique .
the roots were x - rayed to verify the complete filling of the root canal .
the tip of each root was resected perpendicular to its long axis 3 mm from the apex with diamond bur # 1090 ( kg sorensen , so paulo , sp , brazil ) using a high speed hand piece with water coolant using a proper apparatus ( supports developed by the department of restorative dentistry , unesp , so jos dos campos , sp , brazil ) . then apical cavities with the depth of 3 mm were prepared ultrasonically ( nac plus adiel comercial , ribeiro preto , sp , brazil ) by a df 608 diamond tip ( multisonic s gnatus , satelec system n s12.900  gnatus , ribeiro preto , sp , brazil ) .
the root surfaces were covered with two layers of nail varnish ( risqu , taboo da serra , sp , brazil ) up to 2 mm from the apical foramen and then divided into 3 groups with 14 specimens each , according to retrograde filling material used : group 1 : portland cement ( concrebrs , montes claros , mg , brazil ) .
group 3 : sealapex ( kerr corporation , orange , california , usa ) with zinc oxide added .
( odahcam - herpo produtos dentrios ltda , rio de janeiro , rj , brazil ) .
portland cement was mixed by adding distilled water to the powder at the same proportion recommended by the manufacturer of proroot mta .
the sealapex was prepared by mixing equal parts of the base paste , catalyst and zinc oxide until a homogenous color was obtained .
the zinc oxide was then added until uniformity was obtained using 1:1:1 proportion of base paste , part catalyst and zinc oxide .
all materials were inserted into the apical cavity with spatula # 1 adapted with an amalgam condenser , and the excesses removed with sterile gauze .
the roots were externally covered with a layer of approximately 2 mm of sticky wax except for the apical section . in each group ,
two specimens were used as positive and negative internal controls . for the positive control ,
the external root surface of a specimen was not covered with any varnish or wax . for the negative internal control ,
the roots were immersed in simulated tissue fluid ( chloride of sodium-100 mm of chloride of potassium-4 mm ; chloride of calcium-1 mm ; sulfide of magnesium-1 mm ) , buffered and with ph adjusted at 7.4 , maintained at 37c and 100% relative humidity for 30 days . during this period , the tissue fluid was changed weekly using sterile vats and a laminar - flow chamber ( veco of brazil - marconi laboratory equipments  brazil ) . after this period , the roots were removed from the simulated tissue fluid , rinsed with saline solution and immersed in 0.2% rhodamine b dye .
the dye was applied in a vacuum environment of 20 mm hg maintained by a vacuum pump model cal bf  1725 ( dia pump fanen ltda , so paulo , sp , brazil ) connected to a dehumidifier .
the samples were kept in the vacuum for one hour and then were maintained in the dye at 37c and 100% relative humidity for 24 hours .
after the time elapsed for remaining in the dye , the roots were washed in running water , dried and the external layers of varnish and wax were removed .
the roots were then split up to the middle , in buccolingual direction , obtaining two halves with the path of the root canal especially evident in the apical third .
the samples were mounted individually on glass microscope slides and evaluated on a stereomicroscope ( tecnival carl zeiss - jena - germany ) with micrometric measurement ocular for evaluation of the linear dye penetration at the tooth - materials interface .
statistical analysis of the data was accomplished using non - parametric kruskal - wallis test ( p<0.05 )
the results were analyzed by non - parametric kruskal - wallis test at a significance level of 5% .
although the extent of dye penetration was similar in apical cavities obturated with mta and sealapex + zno ( 0.350  0.189 and 0.350  0.584 , respectively ) and highest in portland group ( 0.750  0.897 ) , there were no statistically significant differences between groups ( p>0.05 ) .
the results of the present study showed that the three experimental materials presented similar marginal sealing ability .
the mineral trioxide aggregate ( mta ) was developed by torabinejad , et al.20,1999 , who verified low leakage in retrograde cavities filled with this material . since then , several studies have shown its excellent capacity of marginal sealing when compared with other materials ( abedi and ingle1 , 1995 ; torabinejad , et al.21 , 1995 ; bates , et al.4 , 1996 ; yatsushiro , et al.25 , 1998 ; torabinejad and chivian20 , 1999 ; wucherpfennig26 , 1999 ; aqrabawi2 , 2000 )
. the main components of mta are tricalcium silicate , tricalcium aluminate , tricalcium oxide and silicate oxide .
the powder is composed of small hydrophilic particles and the hydration of the powder results in a colloidal gel that solidifies in the mineralized structure of the tooth ( torabinejad , et al.22,1993 ) , leading to a marginally satisfactory adaptation due to the possible expansion of this material in a humid environment .
the studies of abedi , et al.1,1995 ; holland , et al . 9 , 1998 ; ;
wucherpfennig26,1999 ; estrela , et al.7 , 2000 ; keiser , et al.12,2000 ; holland , et al.10,11 , 2001 were done in order to evaluate the biological compatibility of mta to the periapical tissues when compared to other retrograde - filling materials . in these studies
it was verified that mta presented lower toxicity than super - eba , amalgam and irm , materials traditionally used for retrograde filling ( keiser , et al.14 , 2000 ; abedi , et al.1,1995 ) , as well as providing a favorable treatment for the periapical tissues with new cement formation around them ( zhu , et al.27 , 2000 ; abedi and ingle1 , 1995 ) .
portland cement has shown very similar antimicrobial properties to mta ( estrela , et al.7 , 2000 ) .
besides estrela , et al.7 , 2000 and funteas , et al.8 , 2003 verified that the components of these two cements are similar , except for the presence of bismuth , used to improve radiopacity of mta .
holland , et al.10,11 , 2001 , observed a very similar behavior between portland cement and mta , both inducing mineralized tissue deposition in dogs ' pulps11 and in the connective tissue of mice10 .
however , we can not compare these results with others in the literature since we are dealing with a recent material for endodontic use and many doubts still exist regarding their composition and behavior .
it was also verified that portland cement was similar to mta with regards to manipulation , time of work , consistence and appearance of the material ( estrela , et al.7 2000 ) .
for utilization in root canal filling , it required addition of zinc oxide to allow adequate consistency for insertion into the cavity .
tanomaru filho , et al.19 1998 , observed in vitro better retrograde sealing with sealapex and sealer 26 compared with zinc oxide and eugenol .
this material showed good antimicrobial activity ( tanomaru , et al18 2003 ) and better tissue tolerance in mouse with the sealapex without zinc oxide ( valera , et al.24 ) .
leonardo , et al.15,1997 , studied the evolution of the apical and periapical repair processes after endodontic treatment with calcium - hydroxide based cements , and sealapex was the cement that allowed larger mineralized tissue deposition at the periapical level , being also the only cement capable of accomplishing complete sealing .
also holland , et al.9,1998 , verified in vital pulpectomies in dogs that sealapex presented excellent results , with biological closing of the apex .
tanomaru filho , et al.17,1998 included sealapex in a study of periapical repair in teeth with periapical chronic periodontitis , and the results of histopathological repair were significantly better compared to zinc oxide and eugenol - based cements .
it should be emphasized that the exact clinical importance of leakage studies is still unknown , requiring the use of materials that promote minimal in vitro leakage in association with the biological properties .
the results of this study showed that all materials tested were unable to avid dye penetration . despite the differences between the mean leakage of portland cement compared with mta and sealapex zinc oxide - added cement , all groups were equally ineffective to avoid dye penetration .
 the objective of this study was to evaluate the apical leakage of retrograde cavities filled with portland cement ( concrebrs s / a - mg - brazil ) , proroot mta ( dentsply international , johnson city , tn , usa ) and sealapex ( kerr corporation , orange , california , usa ) with addition of zinc oxide ( odahcam herpo produtos dentrios ltda , rio de janeiro , rj , brazil ) . 
 forty - two extracted single - rooted human teeth were decoronated and used for this study . 
 the root canals were instrumented at 1.0 mm short of the apical foramen using the step - back technique to an apical iso size 60 . 
 the roots were obturated with gutta - percha points and sealer sealapex ( kerr corporation - usa ) and then 3 mm of each root apex was sectioned at a 90 angle . 
 ultrasonic retrograde preparation was performed with a diamond tip to 3 mm depth and the roots were randomly divided into 3 groups according to the filling material : g1-portland , g2-proroot mta , g3- sealapex zinc oxide - added cement . 
 the root surfaces were covered with nail varnish up to 2 mm from the apical foramen , immersed in simulated tissue fluid for 30 days , and then immersed in 0.2% rhodamine b solution for 24 hours for evaluation of marginal leakage . 
 the results showed mean leakage of 0.75 , 0.35 and 0.35 for groups 1 , 2 and 3 , respectively ; however , kruskal - wallis test revealed that there was no statistically significant difference among the results ( p>0.05 ) . 
INTRODUCTION
MATERIAL AND METHODS
RESULTS
DISCUSSION
CONCLUSION