the longevity of a ceramic restoration appears to be linked to its physical and 
 mechanical properties , as well as reliable bonding between the restoration and the 
 tooth . in order to obtain effective bonding between feldspathic ceramics and the tooth 
 substrate ,
surface treatment is necessary for both the internal aspect of the ceramic 
 and the tooth structure .
the use of methods to pretreat the ceramic surface , such as 
 mechanical ( burs and aluminum oxide sandblasting ) , chemical ( 2.5 - 10% hydrofluoric acid 
 etch and silane ) or a combination of both ( silicon oxide sandblasting ) optimize adhesion 
 between the ceramic and the resin cement .
the combination of hydrofluoric acid and silane on the internal surface of the ceramic 
 has been the most recommended method to increase bond strength between the ceramic and 
 the tooth substrate when using resin cements . however , it has been 
 demonstrated that following hydrofluoric acid removal from the ceramic surface , 
 considerable amounts of deposits are formed , which can affect bond strength .
some studies have proposed cleaning techniques for ceramic surface aiming at removing 
 the residues left by hydrofluoric acid etching , including the use of ultrasonic 
 bath , 37% 
 phosphoric acid smear , rinsing under 
 running wateror a 
 combination of 37% phosphoric acid smear and ultrasonic bath . considering the lack of an established protocol to remove residues created by 
 hydrofluoric acid etching of the ceramic surface , the aims of this study were to 
 evaluate :
a ) the micro - shear bond strength and failure mode between the feldspathic 
 ceramic and the adhesive system following pretreatment of the ceramic surface with 
 different cleaning methods to remove particles generated by hydrofluoric acid etching ; 
 b ) the feldspathic ceramic surface micromorphology after using different cleaning 
 methods to remove hydrofluoric acid etching residues by scanning electron microscopy 
 ( sem ) .
forty six feldspathic ceramic discs ( super porcelain ex-3 , noritake kizai co. , ltd , 
 nishi - ku , nagoya , japan , batch 011906 , shade a3,5b ) were made , 6 of which were used to 
 assess micromorphology and 40 were used for micro - shear bond strength testing .
the ceramic discs were obtained from 12.5 mm diameter by 3.6 mm thick wax patterns using 
 lost wax casting , which gave room to the feldspathic ceramic .
the ceramic powder / liquid 
 ratio was used as instructed by the manufacturer and the mixture was placed into the 
 plaster mold using a specific brush provided in the ceramic kit .
the investment plaster 
 and ceramic set were placed in a furnace for sintering at the temperature specified by 
 the manufacturer .
as the ceramic shrinks by approximately 20% during sintering , the 
 final disc dimensions were close to 10 mm in diameter and 3 mm thick .
forty ceramic discs were included in pvc cylinders using polyester resin ( hobby 
 automotivo , 3 m do brasil , sumar , sp , brazil ) .
the surfaces of the ceramic discs were 
 sequentially polished using silicium carbide sandpaper ( lixa d'gua , 3 m , sumar , sp , 
 brazil ) of grades 400 , 600 and 12005 
 , mounted on a running water - cooled electric polisher ( aropol 2v , 
 arotec s / a , so paulo , sp , brazil ) .
the discs were randomly divided into 5 
 experimental groups of 8 discs ( n=8 ) .
the surface of all ceramic discs was treated with 10% hydrofluoric acid ( villevie , 
 joinville , santa catarina , brazil ) for 2 minutes , followed by water and water spray 
 rinse for 30 seconds .
then , the discs were treated according to the experimental 
 groups as follows : group c : no additional surface treatment ; group s : water spray + air for 1 minute , using the 3-in-1 syringe ; group us : ultrasonic bath ( usc1400 , unique ind .
ltda , so paulo , 
 sp , brazil ) with distilled water for 5 minutes ; group f : 37% phosphoric acid smear ( acid gel , villevie , joinville , sc , brazil ) , using 
 a disposable brush ( disposable micro - applicators , microbrush , rio de janeiro , rj , 
 brazil ) for 1 minute , followed by rinsing under running water for 1 minute ; group f+us : 37% phosphoric acid smear ( acid gel , villevie , joinville , sc , brazil ) , 
 using a disposable brush ( disposable micro - applicators , microbrush , rio de janeiro , 
 rj , brazil ) for 1 minute , followed by rinsing under running water for 1 minute , 
 combined with ultrasonic bath ( usc1400 , unique ind e com de prod elet .
ltda , so 
 paulo , sp , brazil ) with distilled water for 5 minutes .
five 0.8 mm diameter x 4 mm high composite resin ( filtek z100 , 3 m espe , st .
therefore , a layer of silane 
 ( dentsply , petrpolis , rj , brazil ) was previously applied to bond the resin onto the 
 ceramic .
a layer of adhesive ( adper scotchbond - adhesive , 3 m espe , st .
paul , mn , 
 usa ) was applied and light - cured using halogen light ( demetron , lc kerr corporation , 
 orange , ca , usa ) for 10 seconds .
then , silicone tubes 4 mm high x 0.8 mm diameter 
 were placed on the ceramic surface to be filled with resin composite . after filling 
 the tubes ,
the resin cylinders were light - cured for 40 seconds ( demetron , lc kerr 
 corporation , orange , ca , usa ) with the light source placed at the upper end of the 
 cylinders , thus light - curing all of them simultaneously .
the light - curing equipment 
 was set at 499 mw / cm ( from 491 mw / cm to 507 
 mw / cm ) with the aid of a radiometer ( radimetro digital , newdent , 
 ribeiro preto , sp , brazil ) and reviewed after every five light - curing cycles . 
 immediately after light - curing , the silicone tubes were cut using a scalpel blade 12 
 and disposed of in order to obtain 4 mm high x 0.8 mm diameter composite resin 
 cylinders bonded to the ceramic surface , with a bonding area of 0.5 mm . 

the specimens were stored in a bacteriological incubator ( ecb 1.3 digital , odontobrs 
 ind .
ltda , ribeiro preto , sp , brazil ) at 37c for 24 hours 
 until the bond strength tests were performed .
the ceramic discs were fixed to a device attached to the universal testing machine 
 ( dl2000 , emic ind e com ltda , so jos dos pinhais , pr , brazil ) .
a 0.3 mm diameter stainless steel 
 wire looped around both the extremity of the loading cell and the composite resin 
 cylinder , simultaneously .
the wire maintained contact with the inferior semicircle of 
 the cylinders , as close as possible to the area bonded to the ceramic .
the test was 
 carried out at a speed of 0.5 mm / min , until bonding failure , for each cylinder 
 sequentially , that is , one at a time .
the failure mode was assessed using a stereoscopic lens ( ek3st model , eikonal , so 
 paulo , so paulo , brazil ) at 20x magnification .
the failure modes were classified as 
 adhesive failure , ceramic or resin cohesion failure , or mixed .
cohesion failure was 
 defined as a fracture in the body of the ceramic or the resin , adhesive failure when 
 there was a fault at the junction between the ceramic and the resin , and mixed when 
 there was both adhesive and cohesion failure , simultaneously .
one of the six ceramic discs used to evaluate surface micromorphology did not receive 
 any surface treatment , including hydrofluoric acid .
the specimens were then stored in an incubator at 50c for 3 hours to remove any 
 water particles , 24 hours prior to sem assessment .
the samples were then placed in 
 airtight glass jars containing silica gel and sealed to ensure moisture 
 elimination .
the discs were positioned in the 
 sem ( jsm 5600lv , jeol , tokyo , japan ) and images were obtained at 500x and 2,500x 
 magnification . for each ceramic disc , the mean micro - shear bond strength value for the resin 
 cylinders was considered .
after exploratory analysis , the data were tested using 
 one - way analysis of variance ( p<0.05 ) on sas statistical software ( release 9.2 , 
 2008 , institute inc . ,
forty ceramic discs were included in pvc cylinders using polyester resin ( hobby 
 automotivo , 3 m do brasil , sumar , sp , brazil ) .
the surfaces of the ceramic discs were 
 sequentially polished using silicium carbide sandpaper ( lixa d'gua , 3 m , sumar , sp , 
 brazil ) of grades 400 , 600 and 12005 
 , mounted on a running water - cooled electric polisher ( aropol 2v , 
 arotec s / a , so paulo , sp , brazil ) .
the discs were randomly divided into 5 
 experimental groups of 8 discs ( n=8 ) .
the surface of all ceramic discs was treated with 10% hydrofluoric acid ( villevie , 
 joinville , santa catarina , brazil ) for 2 minutes , followed by water and water spray 
 rinse for 30 seconds .
then , the discs were treated according to the experimental 
 groups as follows : group c : no additional surface treatment ; group s : water spray + air for 1 minute , using the 3-in-1 syringe ; group us : ultrasonic bath ( usc1400 , unique ind .
ltda , so paulo , 
 sp , brazil ) with distilled water for 5 minutes ; group f : 37% phosphoric acid smear ( acid gel , villevie , joinville , sc , brazil ) , using 
 a disposable brush ( disposable micro - applicators , microbrush , rio de janeiro , rj , 
 brazil ) for 1 minute , followed by rinsing under running water for 1 minute ; group f+us : 37% phosphoric acid smear ( acid gel , villevie , joinville , sc , brazil ) , 
 using a disposable brush ( disposable micro - applicators , microbrush , rio de janeiro , 
 rj , brazil ) for 1 minute , followed by rinsing under running water for 1 minute , 
 combined with ultrasonic bath ( usc1400 , unique ind e com de prod elet .
ltda , so 
 paulo , sp , brazil ) with distilled water for 5 minutes .
five 0.8 mm diameter x 4 mm high composite resin ( filtek z100 , 3 m espe , st .
therefore , a layer of silane 
 ( dentsply , petrpolis , rj , brazil ) was previously applied to bond the resin onto the 
 ceramic . a layer of adhesive ( adper scotchbond - adhesive , 3 m espe , st .
paul , mn , 
 usa ) was applied and light - cured using halogen light ( demetron , lc kerr corporation , 
 orange , ca , usa ) for 10 seconds .
then , silicone tubes 4 mm high x 0.8 mm diameter 
 were placed on the ceramic surface to be filled with resin composite . after filling 
 the tubes ,
the resin cylinders were light - cured for 40 seconds ( demetron , lc kerr 
 corporation , orange , ca , usa ) with the light source placed at the upper end of the 
 cylinders , thus light - curing all of them simultaneously .
the light - curing equipment 
 was set at 499 mw / cm ( from 491 mw / cm to 507 
 mw / cm ) with the aid of a radiometer ( radimetro digital , newdent , 
 ribeiro preto , sp , brazil ) and reviewed after every five light - curing cycles . 
 immediately after light - curing , the silicone tubes were cut using a scalpel blade 12 
 and disposed of in order to obtain 4 mm high x 0.8 mm diameter composite resin 
 cylinders bonded to the ceramic surface , with a bonding area of 0.5 mm . 

the specimens were stored in a bacteriological incubator ( ecb 1.3 digital , odontobrs 
 ind .
ltda , ribeiro preto , sp , brazil ) at 37c for 24 hours 
 until the bond strength tests were performed .
the ceramic discs were fixed to a device attached to the universal testing machine 
 ( dl2000 , emic ind e com ltda , so jos dos pinhais , pr , brazil ) .
a 0.3 mm diameter stainless steel 
 wire looped around both the extremity of the loading cell and the composite resin 
 cylinder , simultaneously .
the wire maintained contact with the inferior semicircle of 
 the cylinders , as close as possible to the area bonded to the ceramic .
the test was 
 carried out at a speed of 0.5 mm / min , until bonding failure , for each cylinder 
 sequentially , that is , one at a time .
the failure mode was assessed using a stereoscopic lens ( ek3st model , eikonal , so 
 paulo , so paulo , brazil ) at 20x magnification .
the failure modes were classified as 
 adhesive failure , ceramic or resin cohesion failure , or mixed .
cohesion failure was 
 defined as a fracture in the body of the ceramic or the resin , adhesive failure when 
 there was a fault at the junction between the ceramic and the resin , and mixed when 
 there was both adhesive and cohesion failure , simultaneously .
one of the six ceramic discs used to evaluate surface micromorphology did not receive 
 any surface treatment , including hydrofluoric acid .
the specimens were then stored in an incubator at 50c for 3 hours to remove any 
 water particles , 24 hours prior to sem assessment .
the samples were then placed in 
 airtight glass jars containing silica gel and sealed to ensure moisture 
 elimination .
the discs were positioned in the 
 sem ( jsm 5600lv , jeol , tokyo , japan ) and images were obtained at 500x and 2,500x 
 magnification .
for each ceramic disc , the mean micro - shear bond strength value for the resin 
 cylinders was considered .
after exploratory analysis , the data were tested using 
 one - way analysis of variance ( p<0.05 ) on sas statistical software ( release 9.2 , 
 2008 , institute inc . , cary , nc , usa ) .

 table 1 describes the mean values of micro - shear 
 bond strength and shows no significant difference between the surface treatment methods 
 ( p=0.3197 ) .
table 2 shows the frequency of 
 failure modes following micro - shear bond strength testing .
mean and standard deviation for bond strength ( mpa ) for the different ceramic 
 surface treatments ( p=0.3197 ) mean followed by same letter indicates no significant difference failure mode for the different ceramic surface treatments when inspecting the sem images , the ceramic surface that received no treatment appeared 
 smooth without porosity , as a result of the polish obtained when the ceramic disc was 
 prepared ( figure 1a ) . regarding the control group 
 ( c ) and the spray group ( s ) , which had the hydrofluoric acid rinsed with water and 
 water - air spray , respectively ,
irregular micrometric structures were observed , which 
 probably consisted of products from the acid etch step ( figures 1b and 1c ) .
such structures 
 were not encountered on the surfaces of the other groups . regarding groups us , f and 
 f+us , no significant difference was observed in terms of surface micromorphology ( figures 1d , 1e 
 and 1f ) .
photomicrographs of the ceramic surfaces as seen using a scanning electron 
 microscope ( sem ) at 500x magnification .
a - unetched ceramic surface ; b - ceramic 
 surface of group c ; c - ceramic surface of group s ; d ceramic surface of group f ; 
 e - ceramic surface of group us ; f - ceramic surface of group f+us . the arrows 
 show residues left following cleaning at higher magnification ( 2,500x ) , groups us and f+us ( figures 2e and 2f ) showed no debris or 
 acid etch residue , whereas , in the two groups in which no ultrasound was used , some 
 debris were still present .
a 
 curious observation was noticed when the phosphoric acid smear was used . at lower 
 magnification
, some darkened areas were observed , which could have been remains of the 
 phosphoric acid itself , which was not completely removed under running water only . at 
 higher magnification , it is obvious that this surface is different from the other 
 groups .
it is likely that some form of over - etching 
 may have occurred on the ceramic surface , when phosphoric acid was applied .
as no 
 ultrasonic treatment was used in this group , the products from over - etching were not 
 efficiently removed .
photomicrographs of the ceramic surfaces as seen using a scanning electron 
 microscope ( sem ) at 2,500x magnification .
a - unetched ceramic surface ; b - 
 ceramic surface of group c ; c - ceramic surface of group s ; d - ceramic surface of 
 group f ; e  ceramic surface of group us ; f  ceramic surface of group f+us .
resin cements and internal ceramic surface treatment are used to promote bonding between 
 ceramic surface and tooth .
such treatments are necessary to modify 
 the surface of these structures , because they are usually smooth and with low surface 
 energy , which prevents the penetration of the bonding agents that create satisfactory 
 chemical or micromechanical retention .
dental ceramics have a crystalline microstructure containing large amounts of loose 
 crystals or granules , which form their microtopography .
feldspathic ceramic is composed of feldspath ( 65% ) , 
 quartz ( 25% ) and metal oxides ( 10% ) .
sodium and alkaline earth oxides are added as 
 bivalent glass modifiers to improve its translucent properties .
potassium oxide 
 ( k2o ) is one of the main components of feldspathic ceramics , which is used 
 to provide the material with a coefficient of thermal dilation as similar as possible to 
 the metal alloys used in metal - ceramic restorations .
the large quantity of glass matrix optimizes the materials 
 vulnerability to acid etching , which allows the formation of microporosities that 
 improve adhesion .
aluminium oxide 
 sandblasting and hydrofluoric acid etching promote an increase of ceramic surface area , 
 creating an irregular topography and increasing surface energy for micromechanical 
 retention of the resin cement .
hydrofluoric acid etching is widely used to pretreat feldspathic ceramic surfaces , 
 because it acts selectively on the silica glass matrix , forming hexafluorosilicates , 
 thus creating a porous surface to facilitate micromechanical interlocking with the resin 
 cement . for feldspathic ceramics ,
surface 
 etching with hydrofluoric acid was used at a concentration of 9% to 10% , and the etching time ranged between 
 one and two 
 minutes .
however , studies comparing etching times reported no 
 difference among the times used , as long as the minimum etching time was one 
 minute .
following etching of silica - based ceramics , it has been observed that hydrofluoric acid 
 leads to the formation of insoluble byproducts , such as silica and fluoride salts , which 
 may remain on the ceramic surface . 

these particles may interfere with the bond strength between the ceramic and the 
 substrate onto which it is cemented . in the present study , the control groups sem images ( which only 
 underwent etching with hydrofluoric acid ) , revealed large quantities of residues when 
 compared to the untreated ceramic and to the groups that received some form of surface 
 cleaning .
however , phark , et al.(2009 ) reported that shear bond strength is not affected by 
 contamination or cleaning procedures , as shown in this study . in order to remove byproducts following hydrofluoric acid etching , some authors used 
 ultrasonic washing , 37% 
 phosphoric acid smear , rinsing with 
 running water , or a 
 combination of 37% phosphoric acid smear and ultrasonic washing .
the present study demonstrated no 
 significant difference in bond strength using different methods of ceramic surface 
 cleaning , despite the presence of byproducts observed by sem following surface cleaning 
 with water spray , unlike in groups us and f+us , in which ultrasonic bath was used . at 
 2,500x magnification ,
ultrasonic washing improved the removal of debris , when compared 
 with the group in which phosphoric acid was used , where residue was observed after 
 rinsing under running water .
however , the longterm effect of this interference has not 
 yet been evaluated . in this study ,
the main failure mode was resin cohesion followed by adhesive failure , 
 thus showing that the hydrofluoric acid residue did not affect bond strength .
( 2009 ) also observed no 
 influence on bond strength from the contaminants left by the etching agent on the 
 ceramic surface .
in addition , fabianelli , et al.(2010 ) demonstrated that the silane application technique is more 
 important than hydrofluoric acid etching .
other studies also have shown increase in bond 
 strength following silane application , regardless of the surface etching 
 technique .
therefore , the residue does not seem to 
 interfere with bond strength , as shown in this study .
regardless of the cleaning technique used on the ceramic surface , the presence or 
 absence of residue following hydrofluoric acid etching did not influence the bond 
 strength between ceramic and resin .
the post - hydrofluoric acid etching cleaning method 
 may simply consist of spraying with water for 90 seconds .
the micro - shear bond strength between the feldspathic ceramic and adhesive system was 
 not influenced by different ceramic cleaning techniques , following hydrofluoric acid 
 etching .
micromorphological evaluation of the ceramic surface revealed little to no 
 residue following hydrofluoric acid etching , when combined with ultrasonic washing .
 objective the aim of this study was to evaluate the effect of feldspathic ceramic surface 
 cleaning on micro - shear bond strength and ceramic surface morphology . 
 material and methods forty discs of feldspathic ceramic were prepared and etched with 10% hydrofluoric 
 acid for 2 minutes . 
 the discs were randomly distributed into five groups ( n=8 ) : c : 
 no treatment , s : water spray + air drying for 1 minute , us : immersion in 
 ultrasonic bath for 5 minutes , f : etching with 37% phosphoric acid for 1 minute , 
 followed by 1-minute rinse , f+us : etching with 37% phosphoric acid for 1 minute , 
 1-minute rinse and ultrasonic bath for 5 minutes . 
 composite cylinders were bonded 
 to the discs following application of silane and hydrophobic adhesive for 
 micro - shear bond strength testing in a universal testing machine at 0.5 mm / min 
 crosshead speed until failure . 
 stereomicroscopy was used to classify failure type . 
 
 surface micromorphology of each treatment type was evaluated by scanning electron 
 microscopy at 500 and 2,500 times magnification . 
 results one - way anova test showed no significant difference between treatments ( p=0.3197 ) 
 and the most common failure types were cohesive resin cohesion followed by 
 adhesive failure . 
 micro - shear bond strength of the feldspathic ceramic substrate 
 to the adhesive system was not influenced by the different surface cleaning 
 techniques . 
 absence of or less residue was observed after etching with 
 hydrofluoric acid for the groups us and f+us . 
 conclusions combining ceramic cleaning techniques with hydrofluoric acid etching did not 
 affect ceramic bond strength , whereas , when cleaning was associated with 
 ultrasound , less residue was observed . 
INTRODUCTION
MATERIAL AND METHODS
Micro-shear bond strength test 
Micromorphological analysis 
Statistical analysis 
RESULTS
DISCUSSION
CONCLUSION