the goal of endodontic treatment is to eliminate diseased pulpal tissue and to create an 
 environment that allows periapical tissues to heal and to prevent the development of 
 apical periodontitis .
affected teeth are retained by removing diseased tissue , sealing 
 the canal system , and subsequently restoring the coronal tooth structure .
although many factors of technical order 
 are involved in the failure of endodontic treatment , the emergence of bacteria that 
 resist therapy and proliferate in the root canal , or that contaminate the canal after 
 endodontic treatment through coronal microleakage , is primarily responsible for 
 unsuccessful treatment .
frequently , the success of endodontic treatment is associated with an appropriate apical 
 sealing .
however , the coronal seal reached using restorations 
 has been considered important . in certain situations
, the filling can be exposed to the 
 oral environment , as in the case of failures or losses of restorations , fractures of the 
 dental structure or the restorative material , or during the intraradicular preparation 
 for post placement .
furthermore , the prosthetic crown may come off , 
 exposing the intracanal post to the buccal environment .
theoretically , any bacteria present in the oral cavity can invade the root canal and 
 participate in the installation of an infectious process . 

enterococcus faecalis , bacterium species frequently isolated in root 
 canals with endodontic failure , represent a small 
 portion of the initial microbiota of teeth with pulp necrosis and periradicular 
 lesions .
this bacterium demonstrates resistance to endodontic 
 disinfection procedures during chemical - mechanic preparation and the 
 capacity to survive in root canals as a single species without the need for a 
 cooperative relationship with other bacteria . despite not simulating some conditions of the oral cavity , as the temperature changes , 

the influence of the diet and saliva flow and the use of human saliva remain the most 
 simulating in a real clinical situation .
the dental literature is increasingly recognizing the importance of the coronal 
 seal . in this context , the 
 importance of an adequate coronal seal in endodontically treated teeth is clear during 
 therapeutic sessions , after filling the root canals , or after placement of the 
 intracanal post and its prosthetic crown .
therefore , the objective of this study was to investigate the recontamination of root 
 canals of endodontically treated teeth prepared to receive an intracanal post , and those 
 with an intracanal post but without a prosthetic crown and exposed to fresh human 
 saliva .
the null hypothesis accepted in this study was that the root canals with 
 intracanal post but without a prosthetic crown can be recontaminated when exposed to 
 fresh human saliva .
these specimens 
 were obtained from the teeth bank of the pelotas dental school ( federal university of 
 pelotas , brazil , rs ) after the ethics committee approved this study ( document no . 

the teeth were stored in 0.9% saline and kept moist at 37c throughout the 
 experiment .
the 
 crowns were removed with a diamond disk in a low - speed handpiece at the level of the 
 enamel - cement junction , except for the teeth in the negative control group , which stayed 
 intact .
a mechanical - chemical preparation 
 following the step - back technique was carried out on the 30 extracted single - rooted 
 human teeth .
the working length was measured by introducing a # 10 k - file ( maillefer , 
 dentsply maillefer ind .
petrpolis , rj , brazil ) into the root canal and 
 establishing it 1 mm from the root apex .
all canals where then instrumented to a size 
 # 20 file at working length . to standardize the diameter of the apical foramen ,
the coronal portion of the canal was prepared with gates - glidden burs # 2 and # 3 . 

1 ml of 1% of hypochlorite ( naocl ) ( wirath indstria e comrcio ltda , so paulo , sp , 
 brazil ) , followed by 1 ml of 17% of ethylenediaminetetraacetic acid ( edta ) ( iodontosul , 
 souza e leonardi ltda .
, porto alegre , rs , brazil ) were used to irrigate the canals 
 between each file to remove organic and inorganic debris . then , 1 ml of sterile saline 
 solution was used ( basa , indstria farmacutica basa ltda .
, caxias do sul , rs , brazil ) 
 to remove tissular debris , complemented by irrigating solutions ( naocl and edta ) .
, baro de 
 angra , paraba do sul , rj , brazil ) previously sterilized to the diameter of the last 
 file size ( # 40 ) .
the root canals were obturated using a lateral condensation technique 
 with gutta - percha cones of size 40 ( as the main cone ) previously disinfected with 1% 
 naocl for 30 minutes and endodontic cement .
, petrpolis , rj , brazil ) , prepared to the appropriate 
 consistency following the manufacturer 's instructions , and was introduced into the canal 
 together with the main and accessory gutta - percha points ( dentsply ind .
when the obturation was concluded , the excess material was removed with a heated paiva 
 condenser along with part of the obturation up to two - thirds of the working length . 

x - rays were taken ( kodak 
 ltda . , so jos dos campos , sp , brazil ) to verify the quality of the filling and the 
 space for the intracanal post and x - ray images were taken of the root filling ( dabi 
 atlante , ribeiro preto , sp , brazil ) with a radiation exposure time of 0.5 s.
the 
 radiographic film was aligned parallel to the long axis of the tooth , and the central 
 beam was directed along the buccal - lingual plane perpendicular to the film .
the teeth were randomly divided into five groups as follows : group 1 ( g1)=10 
 endodontically treated root canals prepared to receive an intracanal post and group 2 
 ( g2)=10 endodontically treated root canals cemented with a prefabricated intracanal post 
 without a prosthetic crown .
five teeth with instrumented root canals , opened access 
 cavities , and not obturated served as positive control group 1 ( pc1 ) , five teeth with no 
 instrumented root canals and access cavities opened served as positive control group 2 
 ( pc2 ) , and five intact ( without endodontic treatment ) teeth served as the negative 
 control group ( nc ) ( figure 1 ) .
flowchart of the experimental groups the root canals of g2 were etched with 37% phosphoric acid ( dentaltec ltda . ,
joinville , 
 sc , brazil ) for 15 s , washed with physiological solution , and dried with sterile 
 absorbent paper points . following conditioning of the root canal dentin , the prime & 
 bond 2.1 adhesive system ( dentsply ind .
ltda . , petrpolis , rj , brazil ) was 
 applied according to the manufacturer 's instructions .
then , carbon fiber posts ( angelus 
 indstria de produtos odontolgicos s / a , londrina , pr , brazil ) were cemented using resin 
 cement ( cement - post , angelus indstria de produtos odontolgicos ltda .
, londrina , pr , 
 brazil ) also according to the manufacturer 's instructions .
all the teeth were kept at 
 37c and in 100% relative humidity for 2 weeks to allow the endodontic cement in groups 
 1 and 2 and the control groups ( pc 1 , pc 2 , and nc ) to reach completely cure .
all 
 samples were sterilized with radiation using a cobalt 60 machine ( embrarad empr .
, et al . ( 2000 ) . a glass tube 
 with rubber stoppers was adjusted for use in this experiment . using a heated 
 instrument ,
a perforation was made in the center of every rubber stopper and one 
 tooth was inserted under pressure up to its cement - enamel junction , to ensure that 
 its crown was outside the vial and its root was within the vial .
cylinders prepared 
 from 10 ml sterile plastic syringes were adapted on the external surface of the 
 stoppers to create a chamber around the crown of the tooth .
then , the glass tube was 
 filled with brain heart infusion ( bhi , acumedia manufacturers , inc . ,
lansing , mi , 
 usa ) sterile broth and the root apex was immersed in the broth .
, itapevi , sp , brazil ) was 
 applied in the interface between the tooth and the stopper to prevent the saliva from 
 penetrating through this space into the bhi broth .
one ml of sterile methylene blue 
 ( 1% ) was placed inside every chamber mounted in adapted plastic syringes to assure 
 the efficiency of the sealing of the cyanoacrylate .
if the medium becomes blue , then the sealing was 
 ineffective and the specimen needs to be discarded .
a parafilm ( american national can , chicago , il , usa ) was used to block the interface 
 flask - stopper of the apparatus .
thirty ml of human saliva was collected from a volunteer at 8:00 a.m. every day of 
 the experiment .
the volunteer did not engage in oral hygiene for at least 12 hours 
 before the saliva collection .
the volunteer chewed a piece of parafilm ( 1 g ) to 
 stimulate salivation .
the saliva was stored in a brown 100 ml glass screw - top 
 container , according to magura , et al .
the chamber of each apparatus was filled with 3 ml of 
 human saliva mixed in bhi broth in a 3:1 ( v / v ) ratio and with 1 ml of the methylene 
 blue dye solution added .
human saliva was changed every 3 days to ensure that the 
 microorganisms did not lack nutrients .
the entire apparatus was aerobically incubated at 37c and 100% relative air 
 humidity , and the appearance of turbidity in the bhi broth was checked daily for the 
 40 days .
the number of days it took for bacterial growth to appear was indicative of 
 the total recontamination of the root canal by bacteria from saliva .
the turbidity 
 was measured visually with the mcfarland scale , trying to approximate the turbidity 
 of inocula to the concentration of cells in a suspension .
care was taken with the 
 evaporation of the bhi broth to keep the roots totally immersed in the medium inside 
 the apparatus during the experiment .
every 48 hours , 4 ml of liquid mixture inside 
 the apparatus chamber were removed and replaced with another 4 ml of sterile bhi 
 broth to avoid saturating the bacterial medium .
data were statistically analyzed using the kaplan - meier survival analysis test and 
 the holm - sidak method .
the apparatus used to evaluate the microleakage was prepared according to siqueira 
 jr . , et al .
a glass tube 
 with rubber stoppers was adjusted for use in this experiment . using a heated 
 instrument ,
a perforation was made in the center of every rubber stopper and one 
 tooth was inserted under pressure up to its cement - enamel junction , to ensure that 
 its crown was outside the vial and its root was within the vial .
cylinders prepared 
 from 10 ml sterile plastic syringes were adapted on the external surface of the 
 stoppers to create a chamber around the crown of the tooth .
then , the glass tube was 
 filled with brain heart infusion ( bhi , acumedia manufacturers , inc . ,
lansing , mi , 
 usa ) sterile broth and the root apex was immersed in the broth .
cyanoacrylate ( super 
 bonder , henkel loctite adesivos ltda . , itapevi , sp , brazil ) was 
 applied in the interface between the tooth and the stopper to prevent the saliva from 
 penetrating through this space into the bhi broth .
one ml of sterile methylene blue 
 ( 1% ) was placed inside every chamber mounted in adapted plastic syringes to assure 
 the efficiency of the sealing of the cyanoacrylate .
if the medium becomes blue , then the sealing was 
 ineffective and the specimen needs to be discarded .
a parafilm ( american national can , chicago , il , usa ) was used to block the interface 
 flask - stopper of the apparatus .
thirty ml of human saliva was collected from a volunteer at 8:00 a.m. every day of 
 the experiment .
the volunteer did not engage in oral hygiene for at least 12 hours 
 before the saliva collection .
the volunteer chewed a piece of parafilm ( 1 g ) to 
 stimulate salivation .
the saliva was stored in a brown 100 ml glass screw - top 
 container , according to magura , et al .
the chamber of each apparatus was filled with 3 ml of 
 human saliva mixed in bhi broth in a 3:1 ( v / v ) ratio and with 1 ml of the methylene 
 blue dye solution added .
human saliva was changed every 3 days to ensure that the 
 microorganisms did not lack nutrients .
the entire apparatus was aerobically incubated at 37c and 100% relative air 
 humidity , and the appearance of turbidity in the bhi broth was checked daily for the 
 40 days .
the number of days it took for bacterial growth to appear was indicative of 
 the total recontamination of the root canal by bacteria from saliva .
the turbidity 
 was measured visually with the mcfarland scale , trying to approximate the turbidity 
 of inocula to the concentration of cells in a suspension .
care was taken with the 
 evaporation of the bhi broth to keep the roots totally immersed in the medium inside 
 the apparatus during the experiment .
every 48 hours , 4 ml of liquid mixture inside 
 the apparatus chamber were removed and replaced with another 4 ml of sterile bhi 
 broth to avoid saturating the bacterial medium .
data were statistically analyzed using the kaplan - meier survival analysis test and 
 the holm - sidak method .
regarding the possibility of recontamination of the root canals , a statistically 
 significant difference was observed among the groups through the kaplan - meier survival 
 analysis test ( p<0.001 ) ( figure 2 ) .
possibility of recontamination of the root canals - kaplan - meier survival analysis 
 test ( p < 0.001 ) this analysis was complemented by the holm - sidak method ( p=0.05 ) , which showed 
 differences among the groups nc and g1 , pc1 and pc2 , and pc1 and g2 .
an analysis of the statistical average of the recontamination time of each group using 
 the kaplan - meier survival analysis test verified that no recontamination occurred during 
 the 40 days of the study in the group of intact teeth ( nc ) . in the group of open teeth 
 and
not instrumented ( pc2 ) , contamination occurred on an average of 1.6 days . in the 
 group of instrumented root canals and
not obturated ( pc1 ) , contamination occurred on 
 average once a day . in the group of teeth prepared to receive an intracanal post ( g1 ) , 
 recontamination occurred on average on 4.9 days , and in the group of root canals that 
 received intracanal posts cemented with resinous cement ( g2 ) but without a prosthetic 
 crown , contamination occurred on an average of 22.4 days ( table 1 ) .
distribution of root canals exhibiting bacterial microleakage after 40 days the root canals instrumented , filed , and prepared to receive an intracanal post and 
 later exposed to fresh human saliva ( g1 ) had an index of 90% ( n=9 ) leakage during a 
 period of 24 hours .
the group of teeth that received an intracanal post cemented with 
 resinous cement and exposed to fresh human saliva ( g2 ) showed that 20% of the samples 
 were recontaminated in 24 hours and 30% in 48 hours ; however , after 14 days , only one 
 more sample showed recontamination . at the end of the 40 days ,
based on the literature , the presence of recontamination of the root canals exposed to 
 human saliva was typically observed , 
 showing the importance of restoration in teeth with a prefabricated intracanal post . 

furthermore , the exposure of endodontically treated teeth to the buccal environment may 
 necessitate endodontic retreatment .
the microorganisms in human saliva can quickly cross the root canal in 
 the absence of coronal sealing , reaching the root apex , and provoking infectious and 
 inflammatory processes in the periradicular tissues .
the group of opened and instrumented root canals used as a positive 
 group ( pc1 ) was penetrated by human saliva microorganisms during a period of 24 h and , 
 as expected , proved that root canals exposed to the oral cavity are infected in a short 
 period . in the group with open teeth and not instrumented ( pc2 ) , the time requested for the 
 apical contamination was longer than for the group with open teeth and instrumented 
 ( pc1 ) .
this result may have been from the instrumentation that provided a more open root 
 canal with the removal of smear - layer and debris , promoting a wider road for the arrival 
 of microorganisms to the root apex without interference , as in teeth not 
 instrumented .
the g1 teeth had an index of 90% of root canal microleakage during a period of 24 h , 
 demonstrating that the 4 mm of remaining filling material did not represent a barrier 
 for the bacterial coronal leakage .
the indicative time of turbidity of the bhi broth for 
 g1 was practically the same as that for instrumented root canals without fillings ( pc1 ) . 
 according to timpawat , amornchat and trisuwan ( 2001 ) ,
most of the endodontic cements have an antibacterial 
 effect that can limit the entrance of bacteria .
certain new sealers , such as epiphany 
 and guttaflow with primer , along with apexit , showed better resistance to bacterial 
 penetration than other new or traditional sealers tested . however , this phenomenon is not in accordance with the 
 results of this study .
( 1991 ) suggested that the presence of zinc in gutta - percha and the 
 endodontic cement used in their study might have inhibited bacterial penetration and 
 growth .
the root canals that received carbon fiber posts cemented with resinous cement 
 experienced a small percentage of bacterial microleakage in the first 24 and 48 hours 
 ( 20% and 30% sample leakage , respectively ) . otherwise , technical failures and 
 microcracks might have helped with this recontamination .
the use of resinous cement 
 could not have prevented the leakage but helped to slow it .
furthermore , in 30% of the 
 samples , complete recontamination of the root canals was not evident during the 40 days 
 of the experiment . despite the advantages of using resinous cements
, the procedure is 
 very sensitive to mistakes such as allowing filling material remnants to stay in the 
 pulp chamber , which would create a difficult acid condition for adhesion . in this study , 

autopolymerized resinous cement was used to guarantee polymerization in the entire 
 extension of the root canal because passing light through the canal is known to be 
 difficult .
definitive restoration should be done preferably as soon as possible , except 
 when the treatment requires a longer period . in this case ,
an adequate temporary 
 restoration should be done and the root canal should be dressed with an antimicrobial 
 material to reduce bacterial penetration .
additionally , the root canal dressing prevents 
 the presence and proliferation of microorganisms that resist the chemical - mechanic 
 preparation of the root canal and protects the periapex .
the findings of this in vitro study show that the contamination of a 
 root canal exposed to fresh human saliva is rapid .
they affirmed that 
 root canals directly exposed to saliva could be quickly recontaminated from the 
 solubilization of the endodontic cement and the permeability of the filling .
however , 
 they could not define when the bacterial leakage provokes an event of periradicular 
 infection , because such an event depends on other factors , including the virulence of 
 microorganisms , defense capacity of periradicular tissues , nutrition , and bacterial 
 interactions .
however , the presence of microorganisms in the periapex indicates that 
 chronic or sharp lesions can grow . despite the limitations of the in vitro leakage tests
the use of human saliva has an 
 advantage because it is faithfully closer to the real clinical situation .
however , it 
 does not simulate similar variables that exist in the buccal environment given 
 temperature changes , the influence of the diet , and salivary flow .
further studies are necessary to 
 investigate the relationship between the leakage of root fillings and the reactions of 
 periradicular tissues .
( 1991 ) evaluated root 
 canals filled and exposed to the oral environment for three months and suggested 
 retreatment of the root canals .
this result is in accordance with the results of the 
 present study , in which the recontamination of root canals without the protection of a 
 coronal restoration and complete filling of the root canal occurred in less than one 
 week .
furthermore , 70% of the root canals that received an intracanal post cemented with 
 resin cement experienced recontamination after 29 days .
however , clinically determining 
 whether contact between saliva and the periradicular tissues continues to contraindicate 
 the definitive dental restoration of a tooth whose root canals remained exposed to the 
 oral cavity for a short period remains impossible .
hence , new studies are extremely important to estimate when a 
 retreatment is necessary for teeth exposed to the buccal cavity .
this study showed that root canals with an intracanal post become recontaminated when 
 exposed to fresh human saliva in a short period .
 objectivethe aim of this study was to investigate the coronal microleakage of 
 endodontically treated teeth prepared to receive an intracanal post and teeth with 
 an intracanal post but without a prosthetic crown and exposed to contamination by 
 fresh human saliva.material and methodsa mechanical - chemical preparation following the step - back technique was carried 
 out in 35 extracted single - rooted human teeth . 
 the teeth were randomly divided 
 into five groups : g1=root canals instrumented , obturated , and prepared to receive 
 an intracanal post ( n=10 ) ; g2=root canals with cemented posts but without coronal 
 sealing ( n=10 ) ; pc1=positive control root canals instrumented and open ( n=5 ) ; 
 pc2=positive control 2 root canals without instrumentation and open ( n=5 ) ; and 
 nc = negative control healthy teeth ( n=5 ) . 
 the crowns were removed except for the 
 control group of intact teeth . 
 the root canals were obturated and sterilized with 
 cobalt 60 gamma irradiation and were then adapted in an apparatus using a brain 
 heart infusion ( bhi ) medium and fresh human saliva for contamination . 
 microbial 
 growth was indicated by the presence of turbidity in the bhi liquid medium.resultsdata were submitted to the kaplan - meier survival analysis and the holm - sidak 
 statistic method , which observed an index of 90% of microleakage in root canals 
 after 24 hours for g1 and 70% of microleakage in samples at the end of 40 days for 
 g2.conclusionthe results show that root canals with an intracanal post but without a prosthetic 
 crown can be recontaminated when exposed to fresh human saliva in a short 
 period . 
INTRODUCTION
MATERIAL AND METHODS
Test of coronal microleakage
Statistical analysis
RESULTS
DISCUSSION
CONCLUSION