the main challenge for a dental adhesive is the ability to bond effectively to two substrates of a different nature .
bonding to enamel is reliable and durable . in contrast , bonding to dentin has been difficult due to its variable nature and heterogenous structure .
hybridization with resin by monomer inter - diffusion has been identified as the basic bonding mechanism resulting in an intimate inter - locking of the cured resin with the dentin .
a wet bonding protocol is advocated for the development of a uniform hybrid layer and better bonding .
after demineralization , collagen fibrils adhere to one another through intra - fibrillar hydrogen bonding .
a solvent with a solubility parameter for hydrogen bonding approximating the amino acid moieties of the collagen fibrils has a better capacity for breaking up these intra - fibrillar hydrogen bonds and expanding the inter - fibrillar spaces to promote wetting and infiltration of the adhesive monomers .
application of acetone produces little solvation force , further affecting the infiltration of resin monomers while alcohol produces progressively higher solvation pressures that develop at increasing rates .
total - etch tertiary butanol based adhesive used in this investigation are thought to maintain the collagen fibrils in an expanded condition after the evaporation of solvents , thus improving infiltration of the monomers .
this study was carried out to evaluate the micro tensile bond strength of the tertiary butanol based two - step adhesive system prime and bond xp and other contemporary adhesive systems to dentin .
this article also discusses other variables affecting bonding such as the origin of dentin substrate , bonding site , area , and aged resin restorations .
the sample comprised of 60 , intact , non - carious , unrestored human mandibular premolars extracted for orthodontic reasons .
teeth were scraped of residue , kept in 2.6% sodium hypochlorite ( naocl ) , rinsed under running water and stored in isotonic saline at room temperature until use .
teeth were embedded in acrylic resin and the occlusal enamel removed perpendicular to their long axis to expose a flat , midcoronal dentin surface using a low speed , diamond disc .
this surface was polished with silicon carbide paper and then rinsed under copious running water to produce the smear layer and immediately dried with moisture free air .
teeth were randomly divided into four groups : 
 group i : comprised 15 bonded with two step bonding agent - single bond ( 3m)group ii : comprised 15 teeth bonded using two step bonding agent - prime and bond xp ( dentsply)group iii : comprised 15 teeth bonded with a single step bonding agent - clearfil s3 bond ( kuraray medical inc.)group iv : comprised 15 teeth bonded using a single step bonding agent - g - bond ( gc corporation ) . 
 
group i : comprised 15 bonded with two step bonding agent - single bond ( 3 m ) group ii : comprised 15 teeth bonded using two step bonding agent - prime and bond xp ( dentsply ) group iii : comprised 15 teeth bonded with a single step bonding agent - clearfil s3 bond ( kuraray medical inc . )
group iv : comprised 15 teeth bonded using a single step bonding agent - g - bond ( gc corporation ) .
bonding agents were applied according to the manufacturer 's instructions and resin composite material built up incrementally to a height of 5 mm .
each increment was light cured for 40 s and finished with sof - lex finishing and polishing discs and specimens stored in distilled water at room temperature .
sectioning was started in the mesio - distal direction , then the tooth rotated at 90 and sectioned in the bucco - lingual direction to obtain beams with an approximate cross sectional area of 2 mm .
these were mounted to a custom acrylic jig and subjected to micro tensile bond strength testing in a universal testing machine with a cross head speed 1 mm / min and stressed to failure .
results were evaluated statistically by anova and student neuman keuls multiple comparison tests and analyzed .
microtensile bond strength values ( mpa ) were calculated from the force at failure divided by cross - sectional area and multiplied by a constant .
results are expressed as mean  sd one way anova analysis was used for group wise comparison followed by the student newman keul 's test .
group i : microtensile bond strength of samples using a single bond ranged from maximum of 38.66 mpa to a minimum of 26.48 mpa with a mean value of 32.66 mpagroup ii : values for samples using prime and bond xp ranged from a 32.20 mpa to 16.92 mpa with a mean of 25.23 mpagroup iii : values of samples using the clearfil s3 bond ranged from 43.25 mpa to 19.87 mpa with a mean value of 32.07 mpagroup iv : samples using g - bond exhibited values from 32.49 mpa to 14.87 mpa with a mean of 24.76 mpa . 
 
group i : microtensile bond strength of samples using a single bond ranged from maximum of 38.66 mpa to a minimum of 26.48 mpa with a mean value of 32.66 mpa group ii : values for samples using prime and bond xp ranged from a 32.20 mpa to 16.92 mpa with a mean of 25.23 mpa group iii : values of samples using the clearfil s3 bond ranged from 43.25 mpa to 19.87 mpa with a mean value of 32.07 mpa group iv : samples using g - bond exhibited values from 32.49 mpa to 14.87 mpa with a mean of 24.76 mpa .
in group i , mean microtensile bond strength value was 32.66 mpa significantly higher than group ii and group iv . in group
ii , mean value was 25.23 mpa significantly higher than group iii . in group iii , mean value is 32.07 mpa significantly higher than group iv
. in group iv , mean value is 24.76 mpa , which was lowest among all the groups .
microtensile bond strength values ( mpa ) were calculated from the force at failure divided by cross - sectional area and multiplied by a constant .
results are expressed as mean  sd one way anova analysis was used for group wise comparison followed by the student newman keul 's test .
group i : microtensile bond strength of samples using a single bond ranged from maximum of 38.66 mpa to a minimum of 26.48 mpa with a mean value of 32.66 mpagroup ii : values for samples using prime and bond xp ranged from a 32.20 mpa to 16.92 mpa with a mean of 25.23 mpagroup iii : values of samples using the clearfil s3 bond ranged from 43.25 mpa to 19.87 mpa with a mean value of 32.07 mpagroup iv : samples using g - bond exhibited values from 32.49 mpa to 14.87 mpa with a mean of 24.76 mpa . 
  group i : microtensile bond strength of samples using a single bond ranged from maximum of 38.66 mpa to a minimum of 26.48 mpa with a mean value of 32.66 mpa group ii : values for samples using prime and bond xp ranged from a 32.20 mpa to 16.92 mpa with a mean of 25.23 mpa group iii : values of samples using the clearfil s3 bond ranged from 43.25 mpa to 19.87 mpa with a mean value of 32.07 mpa group iv : samples using g - bond exhibited values from 32.49 mpa to 14.87 mpa with a mean of 24.76 mpa .
in group i , mean microtensile bond strength value was 32.66 mpa significantly higher than group ii and group iv .
in group ii , mean value was 25.23 mpa significantly higher than group iii . in group iii ,
[ table 1 ] mean microtensile bond strength of group i was 32.66 mpa while that of group ii was 25.23 mpa and that of group iv was 24.76 mpa showing a difference of 7.43 mpa and 7.90 mpa respectively , which was statistically significant ( p < 0.05 ) .
when compared with group iii , which showed a mean of 32.07 , difference was 0.59 mpa ( p > 0.05 ) , which was statistically not significant . comparison with group i [ table 2 ] mean microtensile bond strength of group ii was 25.23 mpa while that of group i was 32.66 mpa and group iii was 32.07 mpa showing a difference of 7.43 mpa and 6.84 mpa respectively , which was statistically significant ( p < 0.05 ) . compared with group ii , which showed mean of 25.23 mpa , difference was 0.47 mpa ( p > 0.05 ) , which was not significant statistically . comparison with group ii [ table 3 ] mean microtensile bond strength of group iii was 32.07 mpa while that of group i was 32.66 mpa and that of group ii was 25.23 mpa showing a difference of 0.59 mpa and 6.84 mpa respectively , which was statistically significant ( p < 0.05 ) . compared with group iv , which showed a mean of 24.76 mpa , difference was 7.31(p > 0.05 ) mpa , which was not significant statistically .
comparison with group iii [ table 4 ] mean microtensile bond strength of group iv was 24.76 mpa while that of group i was 32.66 mpa and that of group iii was 32.07 mpa showing a difference of 7.90 mpa and 7.31 mpa respectively , which was statistically significant ( p < 0.05 ) .
compared with group ii , which showed a mean of 25.23 mpa , difference was 0.47 mpa ( p > 0.05 ) , which was not statistically significant . comparison with group iv
adhesive systems have constantly evolved in areas of ( 1 ) clinical simplicity ( 2 ) reduced application time and ( 3 ) minimized procedural errors . in the interest of saving chair side time , research was directed at formulation of simpler , single step bonding systems combining the conditioning , priming , and adhesive functions into one single application . despite these advantages ,
bond strength to enamel or dentin is an important indicator of an adhesive system 's effectiveness since the bonding layer must support not only composite shrinkage stress , but also occlusal loads in stress - bearing areas , to avoid gap formation leading to micro leakage , secondary caries and post - operative sensitivity .
a micro tensile bond strength methodology introduced by sano in 1994 has become a popular research method , offering the opportunity to test more than one specimen from a single tooth .
results showed that group i exhibited higher bond strength to dentin than other bonding systems followed closely by group iii .
group ii showed significantly lower bond strength and group iv showed the least bond strength among all the adhesive systems compared .
significant difference was seen in the bond strength of group i and groups ii , and iv but , not with the values obtained for group iii in accordance with previous studies conducted .
since an ethanol - based adhesive invariably contains a small amount of water , this extrinsic water together with the increase in intrinsic moisture caused by removal of the smear layer could have resulted in rehydration of the partially collapsed collagen matrix during the adhesive application enhancing the bonding .
significant difference was seen in the microtensile bond strength values between group iii and group ii and group iv , but not when compared with group i. these results could be attributed to : 
 the presence of 10-methacryloyloxydecyl dihyrogen phosphate , which has chemical affinity for dental tissues and chelates favorably to calciumthe clearfil s3 bond formulation includes a proprietary  molecular dispersion technology  , enabling a two phase liquid , hydrophilic / hydrophobic component homogenous state at the molecular level , resulting in reduction of water droplets at the adhesive interface and therefore , a superior bond . 
 
the presence of 10-methacryloyloxydecyl dihyrogen phosphate , which has chemical affinity for dental tissues and chelates favorably to calcium the clearfil s3 bond formulation includes a proprietary  molecular dispersion technology  , enabling a two phase liquid , hydrophilic / hydrophobic component homogenous state at the molecular level , resulting in reduction of water droplets at the adhesive interface and therefore , a superior bond .
there was a significant difference in the microtensile bond strength values between group ii and group i and group iii but not when compared with group iv .
application of acetone produces little solvation force affecting the infiltration of resin monomers while alcohol produces progressively higher solvation pressures that develop at increasing rates , which helps maintain collagen fibrils in an expanded condition improving the infiltration of resin monomers .
significant difference was noted in the bond strength values between group iv and group i and group iii but not when compared with group ii .
porosities or blisters may have occurred at the bonding interface giving low bond strength values .
these blisters occur because most simplified all - in - one adhesives behave as semi - permeable membranes , which may be as a result of water accumulation either caused by an osmotic gradient or by monomer - solvent phase separation upon evaporation of the acetone .
furthermore , the presence of acidic , hydrophilic and hydrophobic monomers into a single solution may compromise the function of each one of these components .
when bonded to dentin , one - step self - etch adhesives still underperform as compared to conventional three - step adhesives .
serious limitation of all - in - one adhesives are as follows : incomplete polymerization and continued demineralization of the adjacent dentin structure in the tubules .
each self - etching adhesive contains its specific functional monomer , which governs its ph and chemical interaction with the residual hydroxyapatite .
other parameters , which influence bond strength values as shown by related studies are as follows
. bond strength and area of the bonded surface are inversely proportional , due to a greater number of defects at the adhesive joint .
variations in bond strength have been seen between buccal and occlusal surface dentin with the former showing greater values due to a lesser number of dentinal tubules .
it has been shown that there is no significant difference between human and bovine dentin if only the superficial layers are used . even during repair of existing restorations , the total - etch systems performed better with the surface preparation of the existing restoration when compared to single step adhesives .
a durable interfacial adhesion between the tooth and biomaterial is essential for an ideal restoration .
ideally , the life - time of a restoration would match that of its host .
in reality , the continuing search for better restorative systems necessitates an awareness of the current materials that might give optimal clinical durability .
this in vitro study needs further in vivo evaluation because the test was carried out using the extracted teeth without regarding the circumstances of the oral cavity under realistic physiological conditions , which may affect dentin bonding .
additional in vivo , in vitro tests and clinical trials are desirable in order to elucidate the effectiveness of these simplified bonding systems .
results suggest that ethanol and water based total - etch adhesive single bond performed superiorly .
there was no significant difference between single bond and clearfil s3 while the single step bonding agent g - bond exhibited comparatively low values .
tertiary butanol based prime and bond xp performed intermediately among the adhesives that were evaluated .
 aim and objective : to compare and evaluate the micro tensile bond strength of different solvent based one step and two step adhesive systems to dentin.materials and methods : sixty recently extracted human mandibular premolars were subjected for the study and divided into 4 groups of fifteen each . 
 the adhesive materials single bond , prime and bond xp , clearfil s3 bond and g - bond were applied to flat dentin surfaces according to the manufacturer 's instructions . 
 after resin composite build up , teeth were sectioned to obtain beams with an approximate cross sectional area of 2 mm2 and stressed to failure . 
 data were analysed statistically by anova and student neuman keuls multiple comparison tests.results:the study demonstrated that single bond has better bond strength to dentin compared to the other adhesive systems.conclusion:ethanol and water based two - step adhesive single bond exhibited significantly higher microtensile bond strength values to dentin among all the adhesive systems tested . 
INTRODUCTION
MATERIALS AND METHODS
Analysis of results
INTER-GROUP COMPARISONS
DISCUSSION
CONCLUSION