webber et al . ( 1978 ) reported that the sealing ability of temporary fillings decreased over time . realizing this , permanent restorative materials ( glass ionomer or composite resin )
were placed as an additional layer beneath these intermediate restorative materials to seal the pulp chamber floor .
however , the pulp chamber often lacks adequate retention to prevent the dislodgement of the restorative material . it may be due to loss of depth due to caries or fracture of the coronal tooth structure .
the root canal rather than the pulp chamber provides a more logical choice for placement of adequate coronal seal .
this method would offer enough bulk of material to seal the canal appropriately without limiting the thickness and retention of the final restoration .
various temporary restorative materials i.e. , intermediate restorative material ( irm ) , pre - formed ductile preparations ( e.g. , cavit ) , temporary endodontic restorative material ( term ) , and permanent restorative materials like amalgam , composite resin , etc . have been used as intracanal plugs . however
, an ideal intracanal barrier has not been identified yet , or perhaps not even developed .
glass ionomer cement has been advocated as an intracanal barrier in situations where microleakage or recurrent caries are likely because of its cariostatic and adhesive properties .
glass ionomer cement has been shown to provide an acceptable coronal seal for up to 3 months .
mineral trioxide aggregate ( white proroot mta ) has been found to have very good biological properties and also shown to have good sealing properties .
however , minimal attempts have been made to evaluate the effectiveness of mta as an intracanal plug to prevent coronal micro leakage .
the purpose of this study was to compare the sealing ability of mta and gic when used over gutta - percha as intracanal sealing materials .
seventy extracted human non - carious and non - restored mandibular premolars with single canal were taken for this study from individuals amongst 20 - 30 years of age .
the teeth were radiographed from facial and proximal views to confirm the presence of single canal .
after removal of soft tissue and hard aggregations from the root surfaces , teeth were stored in saline until used .
the teeth were decoronated with a tapered fissure carbide bur at high speed to a standardized length of 16 mm .
prior to sample selection , all teeth were inspected clinically under 3.5 magnification using magnifying loupes for fractures or defects that would eliminate them from the study . cleaning and
shaping procedures were executed using step back technique described by mullaney ( 1979 ) . in phase
, rest of the canal was prepared in stepping back procedure in 1 mm increments , no .
the coronal and mid - root preparations were done in refining phase iia using gates glidden drills no . 2 , 3 , and 4 .
each instrument was coated with glyde ( dentsply maillefer , ballaigus , switzerland ) before insertion , and 2 ml of 5% sodium hypochorite ( naocl ) was used after each file size . after instrumentation , final rinse was done with 2.5 ml of 17% ethylene diamine - tetraacetic acid ( edta ) followed by 5 ml of 5% naocl and 5 ml saline .
teeth were randomly divided into experimental groups a and b ( 30 teeth each ) and the control groups c and d ( 5 teeth each ) .
group a : teeth were obturated with gutta - percha and zoe sealer using lateral compaction method .
group b : teeth were obturated with gutta - percha and acroseal ( septodont ) , a calcium hydroxide - based sealer with epoxy resin using lateral compaction method .
teeth were obturated in similar manner as in group a. group d : negative control .
teeth were obturated in similar manner as in group a. gutta percha was cut with a heated spoon excavator and vertically condensed right at the orifice opening of the canals .
teeth were then incubated at 37c for 1 week to allow the sealer to set .
four millimeters of gutta - percha was removed from the coronal part of the teeth by using a hot plugger .
radiographs from facial and proximal views were taken using paralleling technique to verify the reduction of gutta - percha radiographically and also to examine if any gutta - percha or sealer remnants present . experimental groups
a and b were further divided into 2 subgroups each ( a1 , a2 , b1 , b2 ) , depending on the sealing material to be used for the coronal seal .
group a1 and b1 : a conventional chemical cured gic ( fuji ii , gc corporation , tokyo , japan ) , was used as intracanal barrier .
four millimeters of the material was placed into the canal using a spoon excavator and a small plastic instrument ; and then condensed using an endodontic plugger .
one sachet of mta ( white proroot , dentsply - maillefer , ballaigues , switzerland ) was mixed with one drop of distilled water on a sterilized glass slab ( according to manufacturer 's instructions ) .
mta was placed into the canal , using a spoon excavator and a small plastic instrument , and then condensed using endodontic plugger .
all teeth were radiographed to ensure adaptation , length , and consistency of the material over gutta - percha filling . in cases where voids were present or the length of material was not adequate , the material was removed and a new mixture was prepared and condensed into the canal .
teeth were incubated at 37c for 48 hours to ensure that the material had properly set .
preparation and obturation was performed as with the experimental group a. no material was placed over the gutta - percha .
preparation and obturation was performed as with the experimental group a. the entire access was coated with two coats of dental varnish and was restored with amalgam restoration .
all root surfaces of experimental and positive control groups were covered with sticky wax leaving only the access opening uncovered .
teeth were decalcified in 5% nitric and for 72 hours with fresh solution used daily .
teeth were then washed for 4 hours under running water and were dehydrated gradually in ascending percentages of ethanol .
first teeth were immersed in 80% ethanol overnight ; then in 90% ethanol in 2 one - hour washes and then in 100% ethanol in 3 one - hour washes .
the degree of coronal microleakage was determined by measuring the linear extent of dye penetration in millimeters from the coronal end of the preparation , using the calibrated stereomicroscope ( c - ds model , nikon ) under 15 magnification .
statistical analysis of the data was performed using spss ( version 15.0 ; spss inc . ,
kolmogorov - smirnov tests revealed that measurement of the amount of dye leakage was normally distributed .
therefore , one - way anova test followed by post - hoc multiple comparison ( bonferroni ) test at 95% confidence interval was used for intergroup comparison .
the mean percentage extent of microleakage on various surfaces ( buccal , lingual , mesial , and distal ) of the teeth for each group is depicted graphically in figure 1a .
the groups with mta plugs ( group a2 , b2 ) exhibited lower leakage than groups with gic plugs ( group a1 , b1 ) irrespective of the sealer used .
the positive control group c , with no intracanal plug showed almost complete leakage ( 15.8 mm ) , while the negative control group d , with amalgam intracanal plug showed no leakage .
mean micro leakage and standard deviation for all the groups ( a ) bar diagram depicting mean values of micro leakage on various surfaces in various groups .
( b ) bar diagram depicting intergroup comparison of mean microleakage the intergroup comparison of mean microleakage is depicted graphically [ figure 1b ] . amongst the experimental groups , group a1 with zoe sealer and gic plug exhibited the highest leakage .
although the leakage was less than the positive control group c ( with no intracanal plug ) , the difference was statistically insignificant ( p > 0.05 ) . amongst the experimental groups , group b2 with mta plug and
although the leakage was higher in comparison to negative control group d ( with amalgam plug ) , the difference was statistically insignificant ( p < 0.05 ) . amongst the groups with mta plugs , teeth obturated using acroseal sealer exhibited significantly lower leakage than the teeth obturated using zoe sealer .
similarly , amongst the groups with gic plugs , teeth obturated using acroseal sealer exhibited significantly lower leakage than teeth obturated using zoe sealer .
the mean microleakage of group a2 with zoe sealer and mta plug was found to be lower than group b1 with acroseal sealer and gic plug although the results were not statistically significant ( p > 0.05 ) [ table 2 ] .
a complete seal of the root canal system is impossible with currently accepted materials and obturation techniques .
it is , therefore , crucial to protect the canal system from bacterial contamination once endodontic therapy has been completed .
the intracanal barriers provides a second line of defence against the bacterial leakage in obturated canals offering enough bulk of material for sealing without compromising the retention of final restoration .
numerous studies have shown that the use of intraorifice barriers in canals filled with gutta - percha significantly decreases coronal microleakage .
the purpose of this study was to compare the sealing ability of mta and gic when placed over gutta - percha obturated root canals as intracanal plugs .
conventional glass ionomer cement ( fuji ii ) was chosen as an intracanal plug in groups a1 and b1 as it has been found to have better sealing ability than resin - modified glass ionomer cement .
the polymerization shrinkage on curing may have been the reason for inferior sealing ability of the resin ionomer .
mta has several clinical applications due to its adequate physical properties , superior biocompatibility , and good sealing ability . in the present study , white mta ( proroot mta )
was chosen as an intracanal barrier material in groups a2 and b2 due to its improved aesthetics and placement characteristics as compared to the original gray mta .
hand condensation can be done with the help of a plugger , paper point or messing gun . in this in vitro study , mta was condensed in coronal 4 mm of root canal using endodontic plugger .
there was adequate accessibility to this region ; therefore , readily available plastic filling instrument and spoon excavator were used to place the material to the site .
teeth were radiographed to ensure there were no voids and to ensure adaptation , length , and consistency of the material over gutta - percha filling .
amalgam was used as an intracanal barrier in negative control group d as it is time - tested and the most commonly used material for comparison with mta when evaluating its apical sealing ability .
although each technique has its proponents , there is no general consensus in the profession as to which technique(s ) is the best . in this study ,
linear dye penetration method was used as it is most convenient , sensitive , easy to accomplish method that does n't require sophisticated materials or equipments and produces results similar to bacterial leakage method .
methylene blue was used in the current study because it has a low molecular weight and penetrates more deeply than other dyes . the clearing technique recommended by okumura in 1927
was used in this study for leakage evaluation . in this technique , the teeth become transparent after the process of demineralization , dehydration , and immersion in methyl salicylate .
it permitted observation of dye along all the surfaces of the specimen without the loss of dental substance , which is not possible in the techniques in which a tooth is sectioned .
it is simple , fast , performed with substances low in toxins , and does not require complex equipment .
the difference in mean microleakage amongst the various surfaces ( buccal , lingual , mesial , and distal ) in various groups was insignificant . the results clearly show that the technique used for biomechanical preparation and obturation was able to prepare and obturate the teeth equally well in all the dimensions irrespective of the oval cross - section of the canal . in the present study , positive control group where no intracanal plug was used permitted leakage along almost the entire length of the canal [ figure 1e ] , while the amalgam intracanal plug in the negative control group allowed no dye penetration through the canal [ figure 1f ] .
the leakage in group with gic plug and zoe sealer was highest amongst the experimental groups .
although this was lower than positive control group with no intracanal plug , the difference was statistically insignificant .
this may be due to poor sealing ability of both the zoe sealer and gic plug .
the leakage in group with mta plug and acroseal sealer was lowest amongst the experimental groups , and the difference was statistically insignificant ( p < 0.05 ) in comparison to negative control group with amalgam plug .
groups with mta plugs exhibited significantly lower leakage than groups with gic plugs irrespective of the sealer ( acroseal or zoe ) used [ figure 1 ] .
this is in accordance with various other studies that reported mta to have better sealing ability than gic .
its sealing ability has been attributed to its hydrophilic nature and expansion when it sets in moist environment .
gap formation between gic and dentin wall resulted in poor sealing ability of gic , which may have been due to material shrinkage on setting .
daoudi et al . found perforations sealed with mta to leak significantly lesser than vitrebond ( rmgi ) .
the potential for air bubble formation resulting in voids might have been the reason for inferior findings of gic . in the study by barrieshi
 nusair et al . , glass ionomer barrier was not well condensed and homogenous and required replacement in 11 of 30 samples .
mta is a condensable material resulting in lesser porosity compared to conventional gic that might tend to entrap air bubbles within while setting resulting in higher leakage . in cases of retreatment and post - preparation ,
however , the results of the present study are contradictory to those obtained by tselnik et al . and john et al . , who found no significant difference in sealing ability between mta and gic when used as intracanal barriers .
when mta plugs were placed , the mean microleakage in teeth obturated with acroseal sealer was significantly lower than in teeth obturated with zoe sealer .
similar results were seen in groups with gic plugs , and the results were statistically significant .
lower score of microleakage exhibited by teeth in which acroseal was used as a sealer may be due to its significantly better sealing ability than zoe .
this removal of smear layer must have facilitated the diffusion of calcium hydroxide resulting in decreased dentinal permeability , hence decreasing the ability of dye to penetrate through the surrounding canal walls .
acroseal , unlike other calcium hydroxide sealers , has lower solubility ; probably because of its epoxy resin component .
acroseal has lower film thickness ( 9 m ) as compared to 95 m reported for rocanal 4 , a zoe sealer resulting in its better sealing ability .
the results of this study showed that mta when placed as an intracanal plug exhibited lower mean leakage than gic irrespective of the sealer used . also , acroseal sealer exhibited better sealing ability than zinc oxide sealer .
hence , mta and gic as an intracanal barrier and sealer with good sealing ability for obturation may be used to minimize microleakage in endodontically treated teeth . however , further research and clinical trials using larger sample size and well controlled in vivo studies need to be done to correlate the results .
 aims : the purpose of this study was to compare the sealing ability of mineral trioxide aggregate ( mta ) and glass ionomer cement ( gic ) when used over gutta - percha as intracanal sealing materials . 
 the study also evaluated the sealing ability of zinc oxide eugenol ( zoe ) cement and acroseal sealer.materials and methods : teeth were obturated with gutta - percha using sealer zoe ( group a , c , d ) and acroseal ( group b ) . 
 the groups were further divided into 2 subgroups ( 15 premolars each ) on the basis of intracanal sealing material used : gic subgroups ( a1 , b1 ) and mta in subgroups ( a2 , b2 ) . 
 the clearing technique was used in this study for leakage evaluation . 
 seventy mandibular premolars were prepared using step - back technique and divided into experimental groups a and b ( 30 premolars each ) and the positive and negative control groups c and d ( 5 premolars each).statistical analysis used : coronal microleakage was determined under stereomicroscope using 15x magnification . 
 data was statistically analyzed using one - way anova followed by post - hoc multiple comparison ( bonferroni).results : mta group leaked significantly less than gic group ( p < 0.05 ) . acroseal exhibited better sealing ability than zoe sealer . 
 teeth with no intracanal barrier showed almost complete leakage.conclusions:mta may be preferred over gic as an intracanal barrier . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION