avaliou - se a infiltrao marginal apical em caninos superiores , obturados com quatro tipos diferentes de cimento , os quais foram imersos em tinta nanquim e mantidos a uma temperatura de 37 c por 96 horas , descalcificados em soluo de cido clordrico a 5% , desidratados em srie crescente de lcoois e diafanizados em salicilato de metila .
para isto , 64 dentes de estoque foram instrumentados pela tcnica " crown - down " , irrigados com soluo de hipoclorito de sdio a 0,5% e divididos em dois grupos experimentais .
os dentes do grupo i foram subdivididos em quatro sub - grupos de oito elementos e obturados cada um deles com os cimentos endofill , n - rickert , sealapex e sealer 26 .
os dentes do grupo ii receberam aplicao adicional de laser er : yag , tendo seus canais radiculares obturados como aqueles do grupo i.
0,01 ) , nos dentes obturados com o cimento endofill , em relao  infiltrao ocorrida nos dentes obturados com os cimentos n - rickert , sealapex e sealer 26 . no houve diferena estatstica significante ( p > 0,05 ) , quanto  infiltrao marginal apical , nos dentes do grupo i , preparados somente com a soluo de hipoclorito de sdio a 0,5% , e naqueles do grupo ii , que foram irradiados com laser er : yag .
a irradiao de laser er : yag aplicada nas paredes do canal radicular no foi capaz de prevenir a infiltrao marginal apical .
this step consists of sealing the entire root canal system with biologically tolerated materials with good physicochemical properties , resistant to microleakage and capable of creating an appropriate environment for tissue regeneration5 so far , however , no material has shown all these desired properties .
thus , to a greater or lesser extent , apical microleakage has continued to occur in endodontic seals7,6,4,2,1,13 .
fachin , et al.6 ( 1995 ) determined the sealing ability of fillcanal , sealer 26 and n - rickert endodontic cements in teeth filled by the lateral gutta - percha condensation technique .
apical microleakage was identified after the treated teeth were immersed in indian ink for 72 hours and then cleaned .
the lowest levels of apical microleakage were observed when the fillcanal cement had been used , followed by the n - rickert and sealer 26 cements .
apical microleakage is characterized by the flow of tissue fluids through the interface between root canal walls and filler materials , which allows for bacterial proliferation and , consequently , leads to irritation of the tooth - supporting tissues . in turn , this causes inflammation especially in the periapical region13 . among the chemical solutions used nowadays
as biomechanical primers in root canals , different concentrations of sodium hypochlorite are the most commonly used .
worldwide , the product is valued for its clearing , organic tissue dissolution , and saponifying properties ; as well as for its capacity to transform amines into chloramines , and to work as a deodorant and an antibacterial agent .
senia , et al.11 ( 1971 ) showed that 5% sodium hypochlorite is efficient in cleaning root canals , except for the apical three millimeters .
takeda et al.17 ( 1998 ) used scanning electron microscopy to study the efficiency of er : yag laser to debride previously instrumented root canal walls .
the authors tested the laser at 1 and 2 w powers and a third , non - irradiated group of teeth was used as control .
the results showed that the laser application at both power levels debrided the root canals and left the dentinal canaliculi open .
in contrast , smear layers were found at all canal levels in the control group , which obstructed the dentinal canaliculi .
the aim of the present study was to determine the effect of er : yag laser irradiation onto the dentinal walls on apical microleakage of root canals filled with different types of sealers by the lateral condensation technique .
sixty - four intact human maxillary canines kept by the dental research laboratory of university of ribeiro preto were used in this study .
the teeth were immersed in 0.1% thymol at 9c , and then washed under running water for 24 hours to remove traces of the thymol solution .
the teeth were cross - sectioned along their axes , leaving a root remnant of 14 mm .
10 k - files ( dentsply , maillefer , ballaigues , switzerland ) inside the root canal until their tip could be seen in the apical foramen , followed by a 1 mm withdrawal , and the measurement of its actual length .
the root canals were irrigated with 0.5% sodium hypochlorite at each instrument change . following the biomechanical preparation of the root canals
teeth in group i were submitted to final irrigation with 10 ml deionized distilled water .
group ii teeth were further subjected to the application of er : yag laser rays ( 7-hz frequency , 200 mj , 300 pulses and 60 j total energy ) and were then irrigated with deionized distilled water .
the canals in each subgroup were filled with the following cements : endofill ( dentsply , herpo , petrplis , rj ) , consisting of zinc oxide and eugenol ; n - rickert ( inodon , porto alegre , rs ) consisting of zinc oxide and eugenol ; sealapex ( kerr , romulus , usa ) , consisting of calcium hydroxide ; and sealer 26 ( dentsply - brasil , petrpolis , rj ) , consisting of epoxy resin .
all teeth were filled using the lateral gutta - percha condensation technique . after being sealed ,
the teeth were immersed in distilled water and incubated at 37c for a period equivalent to three times the time required to harden the cement according to the manufacturer .
the external surfaces of teeth were rendered impermeable through the application of two layers of cyanoacrylate ester , except for the apical two millimeters .
after the coating had dried , the teeth were immersed in indian ink and kept at 37c for 96 hours .
the teeth were immersed in a 5% hcl solution for debridement , and the solution was changed at every 6 hours .
the teeth were dehydrated in increasingly stronger alcohols ( 70 , 85 , 96 and 100% ) for 4 hours each .
apical microleakage was assessed them under a 2.5x magnification optical microscope ( measuroscope , nikon , japan ) using software scion image for windows .
the data on apical microleakage for the teeth treated with 0.5% sodium hypochlorite ( group i ) , and with 0.5% sodium hypochlorite plus er : yag laser irradiation ( group ii ) before root canals were filled with the endofill , n - rickert , sealapex and sealer 26 cements are shown in tables 1 and 2 .
variance analysis revealed a significant difference ( p < 0.01 ) between the various cements used , but not between root canal treatments prior to sealing ( p > 0.05 ) .
no significant differences in apical microleakage were observed between n - rickert , sealapex and sealer 26 ( p > 0.01 ) , while significantly higher leakage was found when endofill cement was used ( p < 0.01 ) .
none of the cements used , nor any of the treatments applied to the root canal walls , was able to prevent apical microleakage totally .
the clearance method was used in this study to analyze apical sealing as determined by microleakage .
this is a simple , easy and inexpensive technique , which allows , according to hasselgren and tronstad 7 ( 1975 ) , three - dimensional viewing of the tooth . like in other studies ,
some factors were taken into account to prevent leakage of the marker agent between dental structures , such as the coating of the external root surfaces with cyanoacrylate ester for proofing .
indian ink was used to show the level of microleakage because it is resistant to acids , alcohols and methyl salicylate .
apical microleakage in the root canal is a complex phenomenon due to the interplay of numerous factors such as the anatomy of the root canal , properties of the irrigating solution , physicochemical characteristics of sealants , and different sealing techniques13 .
since no ideal filling material is currently available , special attention should be paid to the biomechanical preparation of the tooth , for which different irrigating solutions are recommended and new devices enter the endodontic arsenal , all of which are used as support .
it is the interdependence of one treatment step on another that has to be attended to in order for the final results to be optimal .
almost half a century after the discovery of laser beams , their use has become the focus of frequent studies .
laser application combined with irrigating solutions permits the removal of smear layer from the dentinal walls 9,10 , thereby enhancing the adhesion of epoxy resin cements .
however , the results obtained in this study show no significant statistical difference between the two types of treatment applied to the dentinal walls ( 0.5% sodium hypochlorite and 0.5% sodium hypochlorite plus final irradiation with er : yag laser ) .
although sousa - neto14 ( 2005 ) has reported that smear layer removal with er : yag laser increased the adhesion of epoxy resin cements , no decrease in microleakage was reported in teeth filled with sealer 26 cement in the present study . on the other hand , pcora ,
et al.9 ( 1999 ) obtained better permeability results when er : yag laser was applied in combination with distilled water in comparison to the use of a 1% sodium hypochlorite solution , as also reported in the study of sousa - neto , et al .
the two types of root canal wall treatment were prone to apical microleakage , as determined by indian ink penetration in vitro .
the er : yag laser application using the parameters indicated in this study did not reduce apical microleakage when compared to 0.5% sodium hypochlorite .
analyses using tukey 's test revealed the superiority of the n - rickert , sealapex and sealer 26 cements over endofill to provide apical seals .
the er : yag laser irradiation applied to the root canal walls was not able to prevent apical microleakage .
 objectives : the aim of this study was to determine the effect of er : yag laser irradiation used to clean dentinal walls on the apical sealing of root canals filled with different types of sealers.background data : laser application to the dentinal walls removed debris , rendering the root canals free of smear layers and leaving the dentinal canaliculi open.methods:sixty-four maxillary canines obtained from laboratory files were instrumented with k - files ( dentsply , maillefer , ballaigues , switzerland ) using the crown - down technique , and irrigated with a 0.5% sodium hypochlorite solution . 
 the specimens were divided into two groups of 32 teeth each . in group 
 i , the teeth were instrumented and irrigated with sodium hypochlorite solution , and divided into four subgroups to be sealed with the different materials ( endofill , n - rickert , sealapex and sealer 26 ) . in group ii , the root canals were subjected to er : yag laser irradiation ( 200 mj , 7 hz and 60 j total energy ) , followed by root canal sealing as in group i.results:the data showed lower levels of apical microleakage in the teeth filled with n - rickert , sealapex and sealer 26 cements than in those sealed with endofill ( p < 0.01 ) . no significant difference in microleakage was observed between teeth irrigated only with 0.5% sodium hypochlorite and those submitted to er : yag laser application ( p > 0.05).conclusions : the er : yag laser irradiation applied to the root canal walls was not able to prevent apical microleakage . 
Objetivos:
Mtodos:
Resultados:
Concluses:
INTRODUCTION
MATERIAL AND METHODS
RESULTS
DISCUSSION
CONCLUSION