cervical lesions are very often caused by incorrect toothbrushing and dental caries , and usually have little or no enamel at the cervical margin .
flowable composite resins are widely used in clinical practice and are the most common resin materials that recommend for restoring these lesions instead of conventional resin composites .
these materials have good aesthetic properties , and because of low viscosity,[24 ] are easier to place and more self - adaptable compared to stiffer restorative materials .
also , flowable materials may act as a stress - breaker ; therefore , they have been advocated as a gingival liner in class ii composite resin restorations .
the flowable composite resins due to their lower filler content have higher polymerization shrinkage , coefficient of thermal expansion , and inferior mechanical properties .
stresses from shrinkage create forces that compete with the adhesive bond , and this may disrupt the bond to cavity walls , which is still one of the main causes of marginal failure and subsequent microleakage.[911 ] moreover , in cervical lesions , the lack of enamel at the gingival margin aggravates the situation .
however , the importance of perfect seal for success and longevity of class v resin restorations must be considered at the time of restorative treatment .
miyasaka and colleagues found that the shrinkage ratio was less than 1.5% in the conventional composites , but more than 2.0% in the flowable ones .
nevertheless , some studies showed that flowable composite resins produced polymerization contraction stress similar to the hybrid composite . with passing of time ,
new materials and techniques have been developed for tooth restoration to facilitate the daily practice of clinicians .
this material is an alternative to the time - consuming procedure used with traditional materials .
the embrace wetbond ( pulpdent corporation , ma , usa ) is a flowable composite resin and the first moist - bonding restorative resin specifically designed for cervical restorations , where it is often difficult to achieve perfect isolation from moisture .
it is formulated with an advanced , hydrophilic , resin acid - integrating network ( r.a.i.n . ) , and self - adhesive , forming chemical and micromechanical bonds to the tooth structure .
it releases fluoride and has a translucent quality providing excellent aesthetics in the vast majority of situations .
the current flowable composite resins are used along with acid etching and bonding agent routinely . since
cervical lesions are extended to different bonding substrates , enamel at the occlusal and dentin at the gingival margins , bonding of resins to dentin is more difficult and less predictable than bonding to enamel . hence , complete penetration into the entire depth of the demineralized zone and obtaining a reliable bonding is essential to prevent bacterial microleakage and recurrent caries , although some researchers concluded that there was no difference in occlusal or cervical microleakage of cavities restored with flowable or hybrid composite resins .
thus , if a new resin material can be substituted in the application of acid etching and the bonding agent achieves a strong and durable cohesive bond with enamel and dentin , it will be a new change in esthetic dentistry .
to the best of our knowledge , there is limited documentation regarding embrace wetbond . considering the seriousness of the case
, the present study was conducted with the aim of evaluating and comparing the microleakage of class v cavities restored with new self - adhesive flowable composite resin versus different flowable materials and the null hypothesis was that these materials have no difference effect on microleakage .
a total of 70 freshly human maxillary first premolars without decay , cracks or previous restorations extracted for orthodontic purposes were selected , thoroughly cleaned , and stored in physiological saline solution at room temperature for less than 3 months before use . a standard class v cavity ( 3 mm mesiodistal width , 3 mm occlusogingival height , and 1.5 mm axial depth ) was prepared at the cementoenamel junction ( cej ) on the facial surface of each tooth with a 0.5 mm wide 45 beveled enamel margin and a 90 cervical margin ; the gingival margin was placed 1.0 mm below the cej .
utsunomiya , japan ) in a water - cooled high - speed handpiece by the one operator .
the specimens were randomly divided into five groups ( n = 14 ) and restored with different flowable composite resins : groups i and ii with embrace wetbond ( pulpdent corporation ) with and without acid etching and bonding agent , respectively ; group iii flowable compomer ( dyract flow , dentsply , detrey , gmbh , konstanz , germany ) , and groups iv and v with microhybrid ( tetric flow , ivoclar vivadent ag .
schaan , liechtenstein ) and nanofilled ( premise flowable , kerr corporation , orange , ca , usa ) flowable composites , respectively . for all groups except group
ii , the cavities were rinsed with water , etched with 37.5% phosphoric acid etching gel ( kerr gel etchant , kerr corporation ) for 15 seconds , and rinsed with a water jet for 20 seconds ; groups iii , iv , and v were gently air dried to leave the surfaces wet . in group
there was no pooling of water on the cavity , so that slightly moist surfaces were appearing shiny or glossy .
the ethanol - based adhesive system ( optibond solo plus , kerr corporation ) was applied to the cavities for 15 seconds ; after adhesive application and solvent evaporation with gentle air spraying for 3 seconds , it was cured with a light - emitting diode unit ( kerr corporation , middleton , wi , usa ) for 20 seconds according to the manufacturer 's instruction .
group ii was prepared without acid etching and bonding agents , rinsed like group i. flowable materials were placed in a single increment of shade a2 according to the manufacturers instructions and the light curing unit was placed to the buccal surfaces at a close range ( 0 - 1 mm ) and activated at 1000 mw / cm for 20 seconds .
the restorations were finished using water - cooled microfine diamond finishing burs ( d+z , diamant gmbh , lemgo , germany ) for contouring and removal of excess restorative material , and polished with aluminum oxide polisher ( hiluster polishing system , kerrhawe , bioggio , switzerland ) immediately after filling .
the teeth were stored in distilled water at 37c for 1 month , thermocycled for 1500 cycles from 5 to 55c with a 30-second dwell time and a transfer time of 3 seconds .
the root apices of specimens were sealed with sticky wax ; all external surfaces were covered with two layers of nail varnish except for 1.0 mm around the restorations and then immersed in a 0.5% basic fuchsin dye solution for 24 hours .
the teeth were sectioned faciolingually with a low speed diamond saw ( d+z , diamant gmbh ) under water spray .
the dye penetration depth along the cavity wall ( including both occlusal and gingival margins ) was measured with a stereomicroscope ( nikon eclips e600 , tokyo , japan ) at20 magnification .
two independent precalibrated investigators blindly scored dye penetration ( microleakage ) along the tooth - restoration interface and consensus was forced when disagreements occurred .
the microleakage score was recorded separately for both occlusal and cervecal margins on a nonparametric ordinal scale from 0 to 3 as 0 = no microleakage ; 1 = dye penetration less than  of axial wall ; 2 = dye penetration more than  of axial wall ; 3 = dye penetration spreading along the axial wall .
data were analyzed using kruskall - wallis analysis of variance and mann - whitney u - test for comparing the restorative materials ; also occlusal and cervical margins were compared with each other with wilcoxon signed rank test at a 0.05 significant level .
the frequency , mean , and standard deviations of the microleakage scores obtained from the experimental groups for the occlusal and cervical margins are presented in table 1 .
kruskall - wallis analysis of variance revealed significant microleakage differences among the five groups at occlusal margins ( p = 0.001 ) , but not at cervical margins ( p > 0.05 ) .
frequency , mean  sd of microleakage scores , and p value of the wilcoxon signed rank test of the five flowable materials used on occlusal and gingival margins ( n = 14 ) when analyzing the effect of acid etching and bonding agent on embrace wetbond , microleakage at the occlusal margins was significantly less than that without ( p = 0.002 ) , but not at cervical margins . also cavities restored with embrace wetbond without acid etching and
bonding agent showed significantly greater microleakage scores than other groups at the occlusal margin ( p < 0.037 ) , but there was no significant difference at the cervical margin ( p > 0.05 ) .
when comparing each group individually at the occlusal margin , embrace wetbond with acid etching and bonding agent had significantly greater microleakage than premise flowable , but there was no difference with tetric flow and dyract flow , while there was no significant difference between premise flowable and tetric flow .
also dyract flow had significantly greater microleakage than premise flowable , but the difference between dyract flow and tetric flow was not significant . at the cervical margin
, there was no statistically significant microleakage differences between the five groups ( p > 0.05 ) .
a wilcoxon signed rank test showed significantly less microleakage at the occlusal margins compared to the cervical margins in embrace wetbond without acid etching and bonding agent ( p = 0.001 ) , tetric flow ( p = 0.004 ) and premise flowable ( p = 0.023 ) groups , but not in embrace wetbond with acid etching and bonding agent and dyract flow groups ( p > 0.05 ) .
the results of this study showed that none of the tested flowable materials completely eliminated microleakage ; nonetheless it is still a major drawback of flowable materials due to higher polymerization shrinkage and the coefficient of thermal expansion .
also , this study showed that with the exception of embrace wetbond without acid etching and bonding agent , the reminder of the flowable materials under investigation exhibited satisfactory adaptation to enamel margin . in the present study ,
embrace wetbond with acid etching and bonding agent exhibited significantly less microleakage at the occlusal margins than those without .
moreover , the results showed significantly greater microleakage at the occlusal margins compared to the cervical margins in embrace wetbond without acid etching and bonding agent . according to the manufacturer 's claim ,
embrace wetbond evaluated in this study is self - etching to dentin ; however , etching enamel surfaces is indicated , but bonding agents and etching dentin are not required , although they can be used , if desired .
also embrace wetbond without acid etching and bonding agent showed significantly the highest microleakage scores than other groups at occlusal margin .
nevertheless , based on the findings of this study , application of acid etching and bonding agent with embrace wetbond is recommended for better adaptation at enamel margin .
phosphoric acid is capable to etch the enamel and remove the smear layer , led to a deeper penetration of resin monomers and the formation of longer tags ; therefore it improves the stability of adhesives and then provides a durable marginal seal . in the present study
the bonding system that was used ( optibond solo plus , kerr ) is a bonding agent for virtually every clinical application .
it is ethanol - based , 15% filled with 0.4 m filler , and actually reinforces dentine tubules at much greater depths than unfilled or nanofilled systems .
this means a better long - term stability and outstanding bond strengths with direct or indirect applications .
asefzadeh and colleagues showed that shear bond strength of embrace wetbond without application of acid etching and bonding agent was significantly lower than tetric flow composite combined with excite bond .
they concluded that application dentin bonding agents with this flowable composite resin caused the best strength . according to the manufacturers , tetric flow is a fine - particle hybrid composite and given its low viscosity permits optimum wetting of the tooth .
the total content of inorganic fillers is 64.6% wt , or 39.7% vol , and is indicated for class v restorations .
the particle size is between 0.04 and 3.0 m , and the mean particle size is 0.7 m . among the experimental groups the premise flowable exhibited the best marginal adaptation to enamel .
this result should be attributed to the properties of the restorative material , since the other experimental conditions , such as the c - factor of the experimental cavities , the application technique , and the bonding characteristics of the cavity walls , were identical in all restorations except embrace wetbond without acid etching and bonding agent . according to the manufacturer , premise flowable is a medium viscosity , nanofilled , light - cured composite suitable for numerous direct applications .
it has a high filler loading ( 72.5 wt% , 54.6% vol ) , 2.95% shrinkage , and 20% less shrinkage than leading brands , also minimizing stress , sensitivity , and microleakage .
the prepolymerized filler and nanofiller are combined to deliver optimal mechanical strength , durability , and reduced polymerization shrinkage , which might explain the reason of their dye penetration .
on the whole , premise flowable exhibited the lowest microleakage , while embrace wetbond combined without bonding agent presented the highest , and embrace wetbond combined with bonding agent , tetric flow and dyract flow were intermediate at the occlusal margin .
flowable compomers are now considered a distinct class of dental restorative , and are a group of esthetic materials chemically similar to the well - established composite resins .
they were intended to combine the benefits of traditional composite resins and those of glass ionomer cements such as adhesion and fluoride releasing .
dyract flow is an ideal material for small cavities such as class v , and is used with a self - priming adhesive to bond enamel and dentin .
awliya and el - sahn in an in vitro study concluded that almost no gap formation at the interface was observed in cavities restored with grandio flow composite resin .
grandio flow is a nanofilled flowable composite resin which has high filler loading ( 65.6% ) .
this might explain the low volumetric shrinkage of grandio flow and subsequently its resistance to gap formation .
microleakage is more critical in class v cavities as due to the majority of cervical margins these lesions are located in both dentine and/or cementum , which may lead to a weaker marginal seal than that at the enamel surface .
however , it is essential to obtain a reliable dentin bond to the restorative material .
the adhesion between composite resins and dentin is not as strong as with enamel ; therefore the material can be dislodged toward occlusal during polymerization contraction , causing a bad adaptation of the restoration at the cervical margins . in the present study ,
when comparing the occlusal and the cervical margins of the restorations , totally no statistically significant differences of microleakage were observed between the occlusal and gingival margins .
similarly , estafan et al . found no difference in occlusal or cervical microleakage of cavities restored with flowable composite resins . while , individually , higher microleakage scores were detected in the cervical margin when compared to the occlusal margin in groups i and ii , no difference in microleakage scores
was observed in dyract flow and embrace wetbond with acid etching and bonding agent , which can be related to the composition of these two tissues and these flowable materials .
, chimello et al . , and monticelli et al . reported greater microleakage scores at the occlusal margins than cervical margins .
within the limitations of this in vitro study , it may be concluded that in class v cavities the application of acid etching and bonding agent with embrace wetbond provided better occlusal marginal sealing than those without .
however , biomechanical properties improvement , in vitro , and long - term clinical trials studies still are necessary .
 background : regarding the importance of sealing ability of restorative dental materials , this study was done to assess the microleakage of class v cavities restored with a new self - adhesive flowable composite resin and compare to different flowable materials.materials and methods : seventy standardized class v cavities were prepared on the buccal surface of maxillary premolars teeth . 
 the occlusal and the gingival margins of the cavities were located on the enamel and cementum / dentin , respectively . 
 teeth were randomly assigned into five groups ( n = 14 ) and restored with different flowable materials following the manufacturer 's instructions : groups i and ii : embrace wetbond flowable composite resin with and without acid etching and bonding agent , respectively ; group iii : flowable compomer ( dyract flow ) ; and iv and v : microhybrid ( tetric flow ) and nanofilled ( premise flowable ) flowable composite resins , respectively . 
 after finishing and polishing , the teeth were stored in distilled water at 37c , thermocycled , coated with nail varnish , and immersed in a basic fuchsin , and then longitudinally sectioned . 
 dye penetration was examined with a stereomicroscope and scored separately for occlusal and gingival on a 0 - 3 ordinal scale . 
 data were analyzed with kruskal - wallis , mann - whitney and wilcoxon tests ( =0.05).results : embrace wetbond with acid etching and bonding agent had significantly less microleakage at the occlusal margins than those without , but not at cervical margins . 
 also cavities restored with embrace wetbond without acid etching and bonding agent showed significantly greater microleakage scores than other groups at occlusal margin , but there was no significant difference at the cervical margin.conclusion:the application of acid etching and bonding agent with embrace wetbond provided better occlusal marginal sealing than those without at class v cavities . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION