the aim of endodontic treatment is to clean , disinfect and shape the root canals with the purpose of enabling easy and appropriate filling , thus restoring the function of the tooth . for this purpose , removing the agents that cause irritation of the pulp and periapical tissue through biomechanical preparation is needed .
all these stages are particularly important , but the sum of all the stages is the key to successful endodontic treatment .
the final stage of endodontic treatment consists in filling the root canal system completely and compactly with materials that have physical - chemical properties , which are capable of securing hermetic sealing , making marginal leakage difficult , preventing re - infection and creating a favorable biological environment in order to enable periapical tissue repair . in several cases , after root canal filling , the tooth is not permanently restored in the same session , jeopardizing the recently filled root canal due to exposure . the same could be said about conventional endodontic therapy , where temporary restorative materials are extensive used to perform root canal sealing between sessions .
therefore , the placement of a temporary restoration with adequate properties is indispensable to prevent marginal microleakage .
thus , the aim of the present study was to assess coronal marginal leakage of different types of temporary restorative materials used in root canals after endodontic treatment .
the null hypothesis tested was that there would be no difference in the performance of the different materials .
a total of 88 single - rooted human teeth from the tooth bank were used , after previous approval from the research ethics committee of the institution .
the teeth were submitted to the pulp chamber access procedure using spherical diamond bur no .
3 ( kg soresen , barueri , sp , brazil ) coupled at high - speed ms 400 ( dabi atlante , ribeiro preto , sp , brazil ) and finishing was performed with a no .
the biomechanical preparation was performed using the crown - down technique and the apical stop was made with k - type file # 40 ( dentsply - maillefer , ballaigues , switzerland ) . at each change of the instrument ,
the canals were irrigated with 1 ml of 2.0% sodium hypochlorite solution ( biodynmica , ibipor , pr , brazil ) using a disposable syringe and navitip needle ( ultradent , south jordan , usa ) .
after , the canals were dried with absorbent paper points and filled using the lateral condensation technique with endofill sealer ( dentsply , petrpolis , rj , brazil ) .
next , the teeth were randomly separated into four groups ( n = 22 ) and stored in individual receptacles .
the temporary sealing materials tested on each group were as follows : 
 group i : clip f temporary sealing material ( voco , cuxhaven , germany)group ii : bioplic temporary sealing material ( biodinmica , ibipor , sp , brazil)group iii : vitremer temporary sealing material ( 3 m espe , sumar , sp , brazil)group iv : ketak n100 temporary sealing material ( 3 m espe , sumar , sp , brazil ) . 
 
group i : clip f temporary sealing material ( voco , cuxhaven , germany ) group ii : bioplic temporary sealing material ( biodinmica , ibipor , sp , brazil ) group iii : vitremer temporary sealing material ( 3 m espe , sumar , sp , brazil ) group iv : ketak n100 temporary sealing material ( 3 m espe , sumar , sp , brazil ) . to perform coronal sealing , 4 mm of the filling material were removed below the root canal entrance using a no .
5 gattes - gliden bur ( dentsply - maillefer ) , but leaving enough space to place the temporary sealing materials that would fill the entire pulp chamber .
after performing coronal sealing , the root surfaces were made impermeable with cyanoacrylate ester ( scotch - bond , 3 m espe , sumar , sp , brazil ) to prevent dye penetration along the root surface .
next , the specimens were immersed in indian ink ( acrilex , so paulo , sp , brazil ) for 30 and 60 days , 10 specimens for each time interval .
after the immersion period , the specimens were washed under running water for 1 h , dried , and the cyanoacrylate was removed from the root surfaces with the aid of a no .
after decalcification , the roots were washed under running water and placed into alcohol ascendant scale ( 70% , 80% , 92% and 100% ) for 1 h in each scale , followed by immersion into methyl salicylate for the clarification process .
the positive control group differed from the other specimens because it did not receive the temporary sealing material . on the other hand ,
after diaphanization , the specimens were placed on a glass slide and taken to the optical microscope all 03 ( alliance , campinas , sp , brazil ) at 12 magnification to assess the depth of coronal leakage .
the values of coronal marginal leakage were measured in millimeters from the root canal entrance up to the most longitudinal point of dye penetration .
the data of all measurements were submitted to the kruskal - wallis statistical test , at a 5% of level significance , using the software graphpad prism 4.0 ( graphpad software , la jolla , ca , eua ) .
the values obtained for the coronal marginal leakage using different sealing materials may be seen in table 1 .
irrespective of the time intervals , bioplic presented the highest mean values of leakage and vitremer the lowest , however , with no statistically significant difference when compared to each other and to the other materials ( p > 0.05 ) [ figure 1 ] .
mean values ( mm ) and standard deviations of coronal marginal leakage linear coronal leakage measurement under optical microscope .
( a ) test specimen from vitremer group ( lowest microleakage mean values ) . ( b )
test specimen from negative control group ( no dye penetration -arrow ) ( left ) and test specimen from bioplic group ( right )
in the present study , coronal marginal leakage of different types of temporary sealing materials used in root canals after endodontic treatment was assessed .
based on the results obtained , it could be affirmed that the tested hypothesis was accepted , since there was no significant difference in the performance of the different materials .
coronal microleakage between tooth surface and temporary restorative materials can be assessed using different methods , being the dye penetration test the most used .
temporary restorative materials are used in the pulp chamber access to seal the root canal system between visits in endodontic office , until a permanent restoration is performed .
such material should effectively seal the root canal entrance from microorganism 's contamination , be dimensionally stable in the presence of moist and have adequate mechanical properties .
moreover , some treatments require temporary restorations for longer periods than others . in such cases , due to the facility of removal between sessions and lower cost ,
studies demonstrated that in the absence of an adequate coronal temporary seal , contamination of root canal system could occur in less than 3 days .
several studies have shown that these materials are incapable of preventing coronal marginal leakage , leading to root canal contamination and inducing the appearance of periapical lesions .
as found in the scientific literature , the present study demonstrated that the materials tested were incapable of preventing coronal marginal microleakage in any of the samples .
although some studies have found statistical significant differences in the performance of temporary sealing materials against coronal marginal leakage , other studies have not and are in agreement with the present study .
the materials that presented the highest microleakage mean values , clip f and bioplic , have a resinous matrix - based composed of bis - gma , silicon dioxide , groups of dimethacrylates and organic filler particles . according to the manufacturer ,
polymerization shrinkage is minimal and it does not influence sealing , however , in addition to possible minimal shrinkage , they do not present any type of dentin adhesion that could avoid marginal leakage . on the other hand , the materials that presented the lowest mean values of marginal leakage , vitremer and ketac n100 , are glass ionomer - based cements .
the use of glass ionomer cements as temporary restorative materials in endodontics has been investigated for years and studies report favorable results .
glass ionomer - based cements have a chemical bonding capacity due to the adhesion between the carboxylic groups of the polyacids and the calcium ions existent in enamel , dentin and cementum .
therefore , it was probably due to this fact that they were less prone to marginal leakage . moreover , srikumar et al .
in a recent study , immersed teeth in 1% indian ink dye after restoration with several temporary restorative materials and submitted them to bleaching and thermo cycling for 7 days .
the results were demonstrated that zinc phosphate and zinc oxide eugenol - based cements were affected by the bleaching agent action and thermo cycling procedure .
however , minimal leakage values were observed for hydrophilic pre - mixed temporary restorative materials under the same conditions .
the hydrophilic characteristics of both materials ( pre - mixed temporary restorative material and glass ionomer - based cements ) could explain the favorable results observed in the different studies . although there is no a temporary restorative material able to completely avoid contamination for a long period , these materials are capable of minimizing such contamination during and after endodontic treatment . furthermore , none of the materials tested in the present study was capable of preventing marginal leakage within the 30 and 60 days period in any of the specimens .
it was observed that coronal marginal leakage progresses over the course of time , however , with no significant differences in the performance of materials after 30 and 60 days .
this fact allow us to conclude that , irrespective of the period of time used , temporary sealing materials must not be kept in the root canals for a long period of time due to the risk of contamination .
despite the limitations of this in vitro study , it could be stated that the glass ionomer - based cements presented the lowest microleakage values . however , none of the tested materials was able to prevent microleakage for a long period of time .
 aim : the aim of this study is to assess the coronal marginal leakage of three temporary restorative materials used for root canal sealing after endodontic treatment.materials and methods : a total of 88 single - rooted teeth were submitted to biomechanical preparation and filled by lateral condensation technique . 
 after obturation process , the teeth were randomly separated into four groups , being two teeth of each group used as positive and negative control . 
 temporary sealing was performed as follows : gi - clip f ( voco ) ; gii - bioplic ( biodinmica ) ; giii - vitremer ( 3 m espe ) and giv - ketak n100 ( 3 m espe ) . 
 next , the specimens were immersed into indian ink for 30 and 60- days , being 10 specimens for each time interval and then submitted to diaphanization to verify the amount of coronal leakage using a measuring microscope.results:leakage mean values within the 30-day period were as follows : vitremer ( 0.3 mm ) , ketak n100 and clip f ( 0.6 mm ) and bioplic ( 1.7 mm ) . within the 60-day period , 
 leakage means were 1.1 mm , 1.5 mm , 2.2 mm and 2.6 mm , respectively.conclusions:none of the materials was capable of preventing marginal leakage within the 30- and 60-day period . in both time intervals , 
 bioplic presented the highest mean of leakage and vitremer the lowest . 
Introduction
Materials and Methods
Results
Discussion
Conclusion