the lack of practical criteria to manage the optimal degree of wetness on dentin substrate complicates the wet bonding for clinicians . as a result
, it is applied differently among operators and in instructions of the manufacturer so that over - wetting or over - drying may occur instead of ideal moisture on the dentin .
excess water can not be easily evaporated due to low vapor pressure and presence of hema contained in many adhesives , retaining water in the bonding site ; phase separation of resin components may take place .
this residual water is capable of diluting the concentration of adhesive monomers , preventing monomers diffusion to the full depth of the demineralized dentin and adequate polymerization of the monomers inside the collagen network .
subsequently , the formed porous hybrid layer is more susceptible to water degradation over time .
the adverse effects of water on the adhesive interface can be minimized when the etched dentin is kept in a dry state .
dry bonding may be obtained during air drying of the cavity after rinsing by clinician to ensure the frosted etched appearance of the enamel .
however , air drying the demineralized dentin leads to collapsed collagen network . as a result
the formed sub - optimal and porous hybrid layer may account for immediate low bond strength and long - term degradation of resin - dentin bond .
although it seems that dried etched dentin is easily obtained , in clinical situation , air blowing of the smear layer and smear plugs - free dentin for water evaporation leads to increased outward fluid flowing from the pulp .
different studies showed the effectiveness of oxalate solution in blocking the orifice of dentinal tubules .
therefore , it can reduce the outward flow of dentinal fluid during bonding procedure . in this way
, simultaneous tubular occlusion and possible maintenance of the collagen matrix stability in the absence of water can be a beneficial approach to provide high and stable dentin bonding .
ethylene - diamine tetra acetic acid ( edta ) is a molecule containing four carboxylic acids that function as a chelating agent at neutral ph .
some studies reported a favorable effect of edta - conditioning to provide sufficient dentin bond strength .
it is capable of selectively removing hydroxyapatite , preserving the structural stability of the collagen matrix .
this stability is attributed to lack of alteration of the native fibrillar structure of the collagen during dissolving the mineral phase of the dentin .
hence , habelitz et al . suggested that the edta - conditioned dentin may be less affected by air drying due to the presence the unaltered collagen containing most of their intrafibrillar mineral .
based on the above - mentioned points , the interfering effect of water with bonding performance of the simplified etch - and - rinse ( one - bottle ) adhesives may be prevented by the combination of edta - conditioning and occluding effect of oxalate desensitizers during dry bonding without compromising bonding efficacy
. therefore , the aim of this study was to evaluate whether this combination produces the adhesive bond strength similar to that made using conventional wet bonding on acid - etched dentin .
one - hundred and twenty extracted sound human third molars were used in the current study .
the teeth were stored in 1% chloramines t solution for 2 weeks , and then in distilled water at 4c before use . after removing the roots ,
the midcoronal dentin surfaces were exposed by removing the occlusal enamel with a diamond saw ( letiz , 1600 , germany ) under running water .
the flat dentin surfaces were polished with silicon carbide paper to standardize the smear layer .
the specimens were randomly divided into 12 groups of 10 teeth each . in the first four groups , one - step plus ( os ) was used and optibond solo plus ( op ) was applied in the other four groups . in the remaining four groups , adper single bond ( sb )
the bonding procedures were performed as follows : in the control groups 1 , 5 , and 9 ( wet / acid ) , after phosphoric acid etching for 15 s and rinsing , the dentin surfaces were gently air dried for 5 s while leaving the moist dentin .
then , os , op , and sb were applied according to the manufacturer 's instructions , respectively [ table 1 ] .
materials used in the current study in the experimental groups 2 , 6 , and 10 ( wet / edta ) , the dentin surfaces were conditioned with 0.1 m edta solution ( ph 7.4 , merck co. , germany ) for 60 s instead of using the phosphoric acid etching .
the remaining bonding procedures were performed as in respective control groups . in the experimental groups 3 , 7 , and 11 ( dry / edta ) ,
edta conditioning and bonding procedures were performed similar to the previous respective groups , with the exception of dry bonding .
after rinsing , the conditioned surfaces were extensively air dried for 30 s with oil - free compressed air . in control ,
wet / edta , and dry / edta groups , we had removed the pulp tissue prior to preparing the specimens for bonding procedure . in the experimental groups 4 , 8 , and 12 ( dry / edta + ox ) , the bonding procedures were performed similarly to the previous respective groups , only an ox ( bisblock , bisco ) was added to bonding procedures .
after edta conditioning and rinsing , ox was applied and dwelled onto the dentin surfaces for 30 s ; then , the surfaces were rinsed for 60 s and dry bonding was performed . after curing the adhesives for 20 s at 600 mw / cm with a light curing unit ( vip junior , bisco , schaumburg ,
il , usa ) , a resin composite ( z250 ) was placed on the cured adhesive using a cylindrical split mold with a height of 2.5 mm and surface diameter of 2 mm .
two increments of 1 mm and 1.5 mm were applied and separately cured for 40 s. after 24 h water storage and thermocycling ( 1000 times ) , bond strength test was performed .
shear bond strength ( sbs ) was measured with a universal testing machine ( instron z020 , zwick , roell , germany ) . a knife - edge shearing rod at a cross head speed of 1 mm / min was applied to load the specimens until fracture and bond strength in mpa was recorded .
the data were analyzed using two - way analysis of variance ( anova ) and tukey 's honestly significant differences ( hsd ) hsd post - hoc tests for pair - wise comparisons at a significance level of 0.05 .
after testing , the fracture modes were evaluated under a stereomicroscope ( ziess ) at 10 and classified according to the predominant mode of fractures as adhesive , cohesive in dentin , cohesive in composite and mixed , a combination of adhesive and cohesive [ table 2 ] .
the mean bond strength and standard deviations of the 12 groups are presented in table 2 , and the results of two - way anova are shown in table 3 .
the use of edta instead of phosphoric acid did not alter sbs of the three used adhesives .
when dry bonding by edta , os showed significantly lower sbs than those of wet bonding by phosphoric acid or edta ( p < 0.0001 ) while both op and sb revealed similar sbs in the three bonding conditions ( p = 0.91 ) .
results of two way analysis of variance by adding the ox treatment to the dry bonding by edta , a significant reduction in sbs was observed for op ( p < 0.0001 ) , but not for os and sb ( p > 0.05 ) .
sbs of os in dry bonding with or without ox was similar , being significantly lower than wet bonding with phosphoric acid etching ( p < 0.05 ) .
only sb had comparable bond strength in four bonding conditions ( p > 0.05 ) .
the pair - wise comparisons of four bonding conditions for each adhesive ( os and op ) are summarized in table 4 .
results of pair - wise comparisons of four bonding conditions was performed by tukey hsd test for each of two adhesives fracture analysis revealed that most of the fractures of groups 3 and 4 ( os in dry bonding with edta conditioning with or without ox ) and group 8 ( op with ox ) were adhesive mode . in other groups ,
in the current study , three one - bottle adhesives with different solvent content ( acetone and water / ethanol ) and ph were used under four bonding conditions .
edta - conditioning and acid etching revealed similar bond strengths under wet bonding for these adhesives .
the thin edta - demineralized collagen matrix contains intrafibrillar mineral , preserving its spongy and stable state , and hence may improve resin infiltration .
the resultant more homogenous hybrid layer may be strong and could produce a high bond strength due to possible chemical interaction between acidic / functional monomers with calcium in residual mineral within the collagen fibrils .
based on the mentioned properties of edta - conditioned dentin , it was speculated that this dentin is less influenced by dehydration . in the current study , this hypothesis was supported when op and sb were bonded to dried edta - conditioned dentin , but not for os .
acetone - based adhesives are more sensitive to an accurate wet bonding technique than ethanol - based ones and require greater surface wetness due to the high water - chaser effect of acetone .
ethanol / water - based adhesives possess the capability of promoting re - expansion of dried collapsed matrix during the infiltration of solvated resin monomers .
however , a substantial decrease of bond strength to acid - etched dentin was reported for two ethanol / water based adhesives ( excite , op ) following air drying for 10 s. reis et al .
suggested that fluid flowing from the retained moist pulp tissue during dry bonding may account for insignificant reduction of bond strength of sb compared to wet bonding .
more severe dry bonding condition was performed and bond strength was significantly decreased . in the current study ,
the pulp tissue was removed prior to bonding procedures ( except for groups with ox ) similar to the latter study to eliminate the interfering effect of water permeation within the tubules ; however , the bond strength of sb and op was not altered under dry bonding on edta - conditioned dentin .
this finding might indicate more stability of the dried dentin following edta - conditioning compared to acid etching . in clinical situations ,
controlling the level of moisture may practically be more difficult and non - uniform wetness may exist on different regions of dentin surface .
furthermore , re - wetting capability of naturally moisture dentin may mitigate the effects of dry and wet bonding .
hence , the application of ox may be beneficial to occlude dentinal tubules , optimizing different wetness conditions ; in the current study , its compatibility with the adhesives used in dry bonding with edta was evaluated .
the reduced permeability of acid - etched dentin was the result of precipitating calcium oxalate crystals below the demineralized dentin .
thus , ox did not compromise the bond strength of relatively neutral etch - and - rinse adhesives ( such as sb and one - step ) .
however , in two recent studies , ox application decreased bond strength of sb , one - step and scotchbond multi - purpose , but it had no effect on prime and bond nt . in literature , the name of commercial products ( all parts of each product name ) is commonly started with capital letters . nt associated with prime and bond is the name of one commercial product .
we corrected the products names in whole of the article text . according to the results of the current study , ox had an adverse effect on bonding efficacy of op that may be due to low ph of this adhesive .
the higher number of adhesive fractures together with a decrease in bond strength in groups 3 , 4 and 8 may have been caused by the lower bonding effectiveness of these bonding conditions .
therefore , only sb with a relatively high ph and the ethanol / water content exhibited the compatibility with the combination of ox treatment on the edta - conditioned dentin under dry bonding .
dry bonding associated to ox pre - treatment may enhance the removal of solvents and residual water after the application of the adhesive , and formation of resin tags .
however , dry bonding may lead to collapsed collagen matrix in the etched dentin . based on our results
, edta - conditioning possibly improves resin penetration in dry bonding condition for the ethanol / water adhesive , resulting in less fibrils exposure . nevertheless , scanning electron microscopic evaluations are needed to explain these results and actual interaction of different adhesive systems on ox treated dentin in dry and wet conditions .
moreover , edta treatment may extract and inactivate matrix metalloproteinase 's involved in degradation of the exposed collagens .
these long - term effects can be studied in laboratory tests with more simulating in vivo situations such as using a positive pulpal pressure and the presence of fluid flowing .
nevertheless , the need for separate enamel etching , difficult control of edta solution only on the dentin surfaces , and the relatively long time ( 60 s ) needed for its application might be disadvantages in clinical practice .
based on the results of this in vitro study , among the three adhesives used , only an ethanol / water based adhesive with a relatively low acidity could benefit from the association of ox pretreatment and edta - conditioning , in a relatively severe dry bonding technique .
 background : elimination of water entrapment in hybrid layer during bonding procedure would increase bonding durability.aims:this study evaluated the effect of oxalate desensitizer ( ox ) pretreatment on bond strength of three one - bottle adhesives to ethylene - diamine tetra acetic acid ( edta)-conditioned dentin under dry bonding.materials and methods : three adhesive systems , one - step plus ( os ) , optibond solo plus ( op ) and adper single bond ( sb ) were bonded on dentin surfaces under four bonding conditions : ( 1 ) wet - bonding on acid - etched dentin , ( 2 ) wet bonding on edta - conditioned dentin , ( 3 ) dry bonding on edta - conditioned dentin , ( 4 ) dry bonding associated with ox on the edta - conditioned dentin . 
 after storage and thermo cycling , shear bond strength test was performed . 
 data were analyzed using two - way analysis of variance and tukey tests.results:wet bonding with edta or acid etching showed similar bond strength for test adhesives . 
 dry bonding with edta significantly decreased the bond strength of os , but it had no effect on the bonding of op and sb . 
 ox application in the forth bonding condition , in comparison with the third condition , had a negative effect on the bond strength of op , but not influence on os and sb.conclusions:the use of an ox on edta - conditioned dentin compromised the bonding efficacy of os and op under dry bonding but compatible for sb . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSIONS