the crystalline dioxide of zirconium results in zro2 , which possesses the strength of metals in addition to being tooth color . by virtue of these properties , zro2 is also known as ceramic steel . with zro2 ceramics , the conventional techniques of bonding ( i.e. mechanical and chemical bonding ) on silica - based ceramics are not viable . acid etching and traditional silanes , which are essential for mechanical bonding , can not be employed in zro2 microstructure due to lack of silica or any glassy phase .
zro2 can not be dissolved by acids , alkalis , or any dissolving agents by virtue of their chemical inertness .
air abrasion technique , by means of alumina and rotary abrasion method , with diamond burs have been unsuccessfully tried to improve mechanical bonding of zro2 with adhesive cements .
selective infiltration etching ( sie ) , where glassy phase is preamble on the surface , is also being analyzed to improve the bonding ability of zro2 . according to tsuo et al .
( 2006 ) , air abrasion of zro2 ceramics and application of zro2 primers has considerably increased the bond strength of zro2 to the resin cement whereas qeblawi et al .
( 2010 ) stated that silica coated zro2 surface after silanation showed improved bond strength compared to air abrasion .
( 2007 ) stated that sie with low fusing porcelain showed improved bond strength than air abrasion using aluminum oxide .
however , there are no studies to comparatively evaluate the various surface pre - treatment techniques on zro2 ceramics .
hence , present study was undertaken to comparatively assess the microshear bond strength of various surface pre - treatments such as , sandblasting , etching with hydrofluoric ( hf ) acid , sie , and combinations of these pre - treatments on zro2 ceramics bonded to dentin using resin cement .
zirconia blocks ( lot no . 0905150/2 , amann girrbach , germany ) were sectioned into 50 cubical blocks of dimensions 8 mm  2 mm  2 mm using prosthetic die cutting jigsaw .
the blocks were then ultrasonically vibrated in deionized water for 5 min and consigned to five equally sized experimental groups ( n = 10 each ) as follows : 
 group i : ( control ) - no treatment was performed for 10 zro2 specimensgroup ii : the specimens were sandblasted using 150 m grain - sized aluminum oxide particle ( tirupathi industries , palanpur , india ) for 20 s at 3.8-bar pressure .
the tip distance from the surface of the zro2 blocks was maintained at 10 mm .
the tip head was positioned at right angle to the zro2 surfacegroup iii : the specimens were treated as per group ii , and then etched using 9.6% hf acid gel ( azure research lab , kochi , india ) for 60 sgroup iv : the specimens were treated as per group ii and then subjected to a heat - induced maturation / sie ( him / sie ) method .
the bonding surface of the zro2 blocks was covered with a thin film of an infiltration agent .
the infiltration agent to control its viscosity and thermal expansion coefficient ( 10.1  10  /c ) has been composed of a low temperature melting glass loaded with different additives .
the infiltration agent mainly consists of silica and oxygen with traces of titanium , alumina , potassium , rubidium , and magnesium .
the blocks were heated to 750c ( 60c / min ) in an electrical induction furnace ( programat cs , ivoclar vivadent , usa ) , cooled to 650c for 1 min ( 60c / min ) , reheated to 750c for 1 min ( 60c / min ) , and finally , cooled to room temperature .
the residue of the remaining infiltration agent was then vibrated in an ultrasonic bath for 15 min , followed by washing under demineralized water for 5 mingroup v : in addition to group iv treatment , the blocks were etched using 9.6% hf acid gel . 
 
group i : ( control ) - no treatment was performed for 10 zro2 specimens group ii : the specimens were sandblasted using 150 m grain - sized aluminum oxide particle ( tirupathi industries , palanpur , india ) for 20 s at 3.8-bar pressure . the tip distance from the surface of the zro2 blocks
the tip head was positioned at right angle to the zro2 surface group iii : the specimens were treated as per group ii , and then etched using 9.6% hf acid gel ( azure research lab , kochi , india ) for 60 s group iv : the specimens were treated as per group ii and then subjected to a heat - induced maturation / sie ( him / sie ) method .
the bonding surface of the zro2 blocks was covered with a thin film of an infiltration agent .
the infiltration agent to control its viscosity and thermal expansion coefficient ( 10.1  10  /c ) has been composed of a low temperature melting glass loaded with different additives .
the infiltration agent mainly consists of silica and oxygen with traces of titanium , alumina , potassium , rubidium , and magnesium .
the blocks were heated to 750c ( 60c / min ) in an electrical induction furnace ( programat cs , ivoclar vivadent , usa ) , cooled to 650c for 1 min ( 60c / min ) , reheated to 750c for 1 min ( 60c / min ) , and finally , cooled to room temperature .
the residue of the remaining infiltration agent was then vibrated in an ultrasonic bath for 15 min , followed by washing under demineralized water for 5 min group v : in addition to group iv treatment , the blocks were etched using 9.6% hf acid gel .
of the five groups , the zro2 blocks of groups i , ii , and iii were silanated
using metal / zro2 primer for 1 min , while the blocks of groups iv and v were silanated using monobond - s ( batch no .
fifty dentin blocks were prepared 2 mm  2 mm  4 mm in dimensions from caries - free posterior teeth .
the prepared dentin samples were then sanitized in an ultrasonic bath for 15 min to render it free from surface debris accumulated during sectioning .
these samples were then etched using 37% phosphoric acid and rinsed under running tap water .
the samples were then dried and primed using excite dsc and light - cured for 20 s. the zro2 blocks using resin cement variolink ii ( ivoclar vivadent , usa ) were then bonded to these dentin samples and light - cured for 60 s. acrylic jigs were prepared using self - cure acrylic and these bonded samples were mounted on the jigs .
they were then subjected to testing for microshear bond strength using universal testing machine at a crosshead speed of 1 mm / min .
the data obtained were then tabulated and statistically evaluated using one - way anova followed by tukey hsd post - hoc test .
according to the results obtained [ table 1 ] , group i ( control ) shows micro shear bond strength ( msbs ) value ( 8.88 mpa ) less than the experimental groups ( ii to v ) . among the experimental groups tested
, no statistical significant difference exists between the mean msbs of groups ii ( 10.12 mpa ) and iii ( 11.04 mpa ) . among the mean msbs of groups iv ( 29.24mpa ) and v ( 31.23 mpa ) ,
mean ( sd ) microshear bond strength of various surface pretreated zirconia blocks bonded to dentin using resin cement the mean msbs of groups iv and v were statistically greater than groups i , ii , and iii .
zirconia frameworks are insoluble to strong acids , alkalis , and organic / inorganic dissolving agents by virtue of their chemical inertness .
the bond strength of different cements on zirconium oxide ceramic surface prior to various pre - treatments has been evaluated by many authors , whereas the combination of these surface pre - treatment has not been studied at large .
hence , the aim of this research was to comparatively evaluate the microshear bond strength of different  surface pre - treated 
tetragonal zro2 polycrystals ( tzp zro2 [ amann girbac , germany ] ) also known as yttrium - stabilized zro2 is currently the most considered zro2 for ceramic restorations and hence was used in this study .
dentin blocks were used in this study as a bonding substrate rather than composite blocks in order to simulate the clinical situation . in group
i ( control ) , no surface pre - treatment was done on the zro2 samples .
the zro2 blocks were coated with metal / zro2 primer and then bonded to dentin blocks using resin cement .
this baseline value was used to compare the efficacy of other surface pre - treatment methods followed in this study . the methodology and
to v , the zro2 samples were sandblasted using 150 m aluminum oxide particles for 20 s at 3.8 bar pressure and coated with metal / zro2 primer .
( 2006 ) in group iii , after sandblasting etching with 9.6% of hf acid for 60 s was done to the zro2 samples as suggested by piascik et al .
this was done by coating low fusing porcelain on the zro2 surface and subjecting it to him at 750c as recommended by aboushelib et al .
after the sie treatment , the zro2 samples of group v was etched using 9.6% hf acid gel similar to group iii .
all the zro2 ceramics were bonded to dentin using resin cement , and the msbs evaluation was done by placing the bonded zro2 ceramics in the universal testing machine . among the experimental groups ,
no statistically significant difference exists between groups ii and iii when compared with the group i ( control ) . for ceramics containing silica particles , the micro - porosities
/ roughness can be created on the surface for adequate bonding , whereas the surface of zro2 ceramics is free of silica particles ; hence , the bond strength of the zro2 ceramics treated with hf acid does not show any significant increase .
the mean msbs of group iii obtained in this study were similar with the studies done by casucci et al .
( 2008 ) . however , when compared to groups i ( control ) , ii and iii , groups iv and v showed statistically significant increase in bond strength values . the mean shear bond strength value obtained in group iv was similar to the study done by aboushelib et al .
a significant amount of silica in the bonding surface is essential for adequate ceramic bonding which are sustained by chemical bonds .
resin cement and ceramic are chemically adhered by means of silanes , which are bifunctional compounds that encourage chemical bonding between dissimilar materials .
organo - silanes copolymerize with the organic matrix of resin cement by means of a degradable functional group create the chemical bonds necessary for the successful bonding of resin cement to dental ceramics .
the surface energy and the wettability of ceramic surfaces are also increased by the silanes which ensure better mechanical and chemical bonding . to achieve this ,
sie was examined to produce a retentive surface architecture on the zro2 ceramics . the main difference between sie and other common surface roughening methods like
airborne particle abrasion is three - fold : primarily , without any applied external mechanical stresses it is self - introduced by the material , secondarily , it happens on the ultra - structural grain level without any structural defects or loss of material , and finally , it generates three - dimensional retentive features where the adhesive resin can infiltrate . in this method ,
the low fusing glass particles which were coated over the bonding surface and fired at 750c , infiltrates into the grain boundaries of the zro2 surface and forms a glassy mesh which is responsible for increasing the bond strength of the zro2 ceramics significantly .
the marginal increase in the mean msbs value of group v ( 31.23 mpa ) was not statistically significant when compared to the group iv .
this could be because the infiltration of the glass phase into the zro2 ceramics at the grain boundaries by sie was limited to only 810 m , which may not be sufficient for the action of hf acid etching to improve the bond strength significantly . to summarize this study ,
the msbs of all the experimental groups is in the following order : group v  group iv > group iii  group ii  group i.
further hf acid etching on sie - treated zro2 did not improve the bond strength significantly . conventional methods such as sandblasting and hf acid etching alone did not achieve clinically satisfactory bond strength values .
 objectives : to comparatively assess the micro shear bond strength ( msbs ) of dentin bonded surface pre - treated zirconia ceramics.materials and methods : zirconia blocks were sectioned into 50 cubical blocks . 
 the blocks were further categorized into five groups ( n = 10 each ) . 
 group i : no treatment was performed on zirconia samples ; group ii : the zirconia samples were sand - blasted ; group iii : group ii + etched with 9.8% of hydrofluoric ( hf ) acid for 60 s ; group iv : the sandblasted zirconia samples were selectively infiltrated with low fusing porcelain ; and group v : group iv + etched using 9.8% hf acid gel . 
 the zirconia specimens were then bonded to dentin samples , and the samples were tested for msbs evaluation using universal testing machine.results:the msbs of all the four experimental groups shows greater value than group i. among the experimental groups , group v and group iv do not show any statistical significant difference , whereas the mean msbs of groups iv and v were statistically greater than group iii and group ii . 
 however , groups i , ii , and iii do not show any statistical significant difference in mean msbs values between them.conclusion:selective infiltration etching of zirconia ceramics provides the highest bond strength with resin cement . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION