determinar a rugosidade de superficies submetidas a diferentes tratamentos e correlacionar rugosidade com velocidade de escoamento de sistemas adesivos
lminas de vidro foram utilizadas como substrato para avaliar a velocidade de escoamento dos sistemas adesivos single bond and prime & bond nt .
seis diferentes tratamentos de superfcie foram comparados : 1- sem tratamento ; 2  silanizao ( sl ) ; 3  jateamento ( j ) ; 4  j + sl ; 5  condicionamento com cido fluordrico a 10% ( hf ) ; 6  hf + sl .
antes e aps os tratamentos , foi mensurada a rugosidade das superficies ( ra , m ) . gotas de 10 l de adesivo foram despositadas sobre as superficies e as velocidades de escoamento foram observadas
significncias estatsticas entre grupos foram analisadas pelos testes anova ( um e dois critrios ) e snk .
houve diferenas significantes na velocidade de escoamento entre materiais ( p < 0.001 ) e entre tratamentos ( p < 0.001 ) .
silanizao diminuiu a velocidade de escoamento para ambos os adesivos em comparao aos grupos no silanizados ( p < 0.05 ) .
houve diferena entre rugosidades inicial e final somente para o grupo jateado , que se apresentou como o mais rugoso ( p < 0.05 ) .
. regresso linear no indicou correlao entre velocidade de escoamento e rugosidade ( r = 0.173 ) .
embora os tratamentos de superfcie tenham produzido diferentes rugosidades , no produziram diferenas na velocidade de escoamento dos sistemas adesivos estudados .
ceramics are , in many cases , the first choice materials for indirect restorations due to their biocompatibility with oral tissues as well as to their good esthetic properties28 .
however , it is also noticing that these materials commonly fail under function due to their brittle characteristics .
a better adaptation between luting cements and ceramics can overcome the possibility of cohesive failures in the structure of the later , improving their stability in the oral environment28 .
thus , it is necessary that luting cements present adequate mechanical properties to avoid postcementation failures , and , for this reason , the resin cements can be the best choice when compared to glass ionomer and zinc phosphate cements28 .
cementation using resin - based cements requires appropriate chemical or mechanical treatment of all substrates involved , i.e. enamel , dentin and dental porcelains , to allow bonding between teeth and indirect restorations .
this bonding process is strongly dependent of some substrate characteristics like surface free energy and roughness as well as resin adhesive properties , such as surface tension and viscosity16 . mechanical or chemical surface treatments seem to raise facilities on the spreading of low viscous materials on a surface23 since they change substrate characteristics .
most of these treatments promote an increasing in porosity and roughness of dental ceramics , improving wettability .
rougher surfaces have wider contact areas available for bonding , and also provide an increased surface free energy in comparison to flatter or smoother ones16,23 .
therefore , a rough topography of a surface may facilitate adhesives ' spreading and substrate 's wettability16,22,23 . some of the most used treatments to create physical modifications on ceramic surfaces are sandblasting22,23 and hydrofluoric acid etching9,22,23,28 .
although these treatments may facilitate adhesion , their can also introduce defects on ceramics structures , which in turn can act as stress raisers , negatively affecting the material mechanical properties29 .
these defects can be produced by vestiges of the etching treatment9,23 or by microcracks created during sandblasting18,29,30 .
these events can compromise the integrity of a ceramic restoration submitted to masticatory forces23 and their severity are dependent of the composition and the microstructure of each type of ceramic1 .
removal of acids vestiges can be made using an ultrasonic bath9 , as well as microporosities can be diminished by a silane plus an adhesive system application25 .
silanization also allows a chemical adhesion between ceramics and resin cements , thus facilitating and improving bonding9,19,21,25 .
several works have studied the principles of adhesion ( surface free energy , contact angle , surface roughness and wettability ) but there are few studies correlating adherends ' roughness and adhesives flow capacity .
although the flow capacity can not be directly correlated to wettability , it is quite important to understand how an adhesive spreads over an inclined surface once the clinical relevant surfaces are not totally flat .
there are few studies that use , instead of water , a clinical relevant adhesive agent to measure contact angles or to evaluate wettability22 .
it is known that water creates lower contact angles with the surfaces than adhesive resins , wetting better the dental substrate22 .
hence , it was decided to investigate an adhesive as the wetting agent and to verify its spreading ability over an inclined surface . in this research ,
the surface chosen to study the spreading phenomenon was a glass slide due to its low cost and sio2 percentage content similar to that of some ceramics13 .
the aim of this study was to determine the surface roughness created by different surface treatments and to correlate it with the spreading ability of two commercial adhesive systems , with or without previous surface silanization .
the null hypotheses advanced here were : 1 ) there is no difference on the roughness created by different surface treatments ; 2 ) there is no difference on the spreading velocity of different adhesive systems ; 3 ) there is no difference on the spreading velocity of the adhesive systems over the surfaces when they are submitted to different treatments and 4 ) there is no correlation between surface roughness and adhesive systems spreading velocity .
surfaces of glass slides ( 25 x 0.8 x 1.1 mm ) ( corning , mx , mexico ) were used as substrates to evaluate the flow capacity of two adhesive systems ( single bond , 3 m espe dental products , st paul , mn , usa and prime & bond nt , dentsply ind .
ltda , petrpolis , rj , brazil ) ( table 1 ) , by means of spreading velocity measurements . the surfaces were previously treated with hydrofluoric acid or sandblasting , both with and without posterior silanization ( figure 1 ) .
ltda , petrpolis , rj , brazil ) , were etched for 4 min and then rinsed with air / water spray for 30s . after rinsing
, the specimens were cleaned for 1min with distilled water in an ultrasonic bath ( ultrasonic cleaner usc 700 , unique ind .
the sandblasted groups were submitted to 50 mm aluminum oxide particles at 35 psi and at a distance of 50 mm from the sandblaster nozzle tip ( 2 mm in diameter ) until the surface exhibited an observable white opaque appearance22 .
then , the glass slides were rinsed with air / water spray for 30 s and cleaned in the ultrasonic bath for 1 min9 . before and after surface treatments ( one per glass slide ) , the surface roughness of each specimen was measured by means of a profilometer ( hommel tester t1000 , hommelwerke gmbh , vs - schwenningen , germany ) .
five readings were made for each specimen and the ra ( arithmetic mean deviation of the roughness profile ) was calculated in microns with a 4.8-mm cutoff value .
the spreading velocity of each adhesive system was measured on a surface inclination of 45. this was performed using a protractor and a base to support the glass slides .
a metallic millimeter ruler was put on the back of each glass slide to allow measurements of the distance traveled by the adhesive systems during their flowing .
for some groups , a silane agent ( silano agente de unio , dentsply ind .
ltda , petrpolis , rj , brazil ) was applied twice over the glass slide with a microbrush for 15 s and dried , following the manufactures ' instructions .
drop volumes of 10 l from each adhesive system were placed over the glass slides with a micropipette ( pipetman , gilson medical electronics s.a . ,
france ) and the spreading of each drop was observed for 30 s , and reported as millimeters per second ( mm / s ) .
measurements were performed five times in each individual glass slide , according to the surface treatment protocol established for each group .
the measurements were made after the glass slides had been cleaned with household detergent , to avoid a greasy surface .
after that and before each measurement , an acetone - soaked gauze was used to remove vestiges of adhesive systems , and then the glass slide surface was air - blow dried .
acetone was used to remove silane and adhesive from the surfaces as it apparently does not influence bonding7 , thus not interfering with the measurements .
the experiments were carried out at both controlled room temperature ( 25  1 c ) and relative humidity ( 50  5% ) .
data were analyzed by a two - way anova design , considering materials and surface treatments as independent variables . to compare roughness from all groups , a oneway anova test was used .
multiple post hoc comparisons were performed using the student - neulman - keuls test ( snk ) .
linear regression was applied to observe the existence of a possible interaction between spreading velocity and roughness .
regarding spreading velocity , the two - way anova test indicated statistically significant differences between adhesive materials ( p < 0.001 ) as well between treatments ( p < 0.001 ) ( table 2 ) .
no significant differences were found among groups when the interaction between materials and treatments was considered ( p = 0.097 ) .
snk test showed that single bond presented a lower spreading velocity than did prime & bond nt , irrespective of the surface treatment employed ( p < 0.05 ) .
silanization decreased spreading velocity means for both adhesive systems tested ( p < 0.05 ) . the one - way anova test indicated statistically significant differences between surface treatments employed when roughness was considered as the testing variable ( p < 0.05 ) ( table 3 ) .
the post - hoc test showed that rougher surfaces were found only when sandblasting was employed ( p < 0.05 ) .
silanization decreased surface roughness of sandblasted surfaces ( p < 0.05 ) , but these surfaces still remained rougher than the non - sandblasted ones .
any difference in roughness was found among untreated , silanated , etched and etched / silanated surfaces ( p > 0.05 ) .
linear regression did not indicate any interaction between spreading velocity and roughness ( r = 0.173 ; rsqr = 0.0299 ) .
the selection of glass slides as substrates for the measurement of both adhesive spreading velocity and surface roughness was due to their low cost , compared to dental ceramics , and also by they vitreous composition ( sio2 ) , similar to that found in feldspathic porcelains13 .
glass has been already used to study silane adhesion10 . according to the adhesion principles , adherend surface free energy and roughness as well adhesive surface tension and viscosity
although wettability can not be directly correlated to spreading velocity , it is supposed that higher spreading velocities yield better wettabilities .
even though adhesive resins are the most clinically relevant agents to measure contact angles ( considering adhesive restorations ) , studies have been frequently using water for this purpose instead of them22 .
however , resins yield higher mean contact angles than water , and therefore do not wet ceramics as well as water22 . according to the results found here ,
the mean spreading velocity found for single bond was significantly lower than that of prime & bond nt , regardless of the surface treatment used .
although we did not measure the viscosity of the adhesives employed in this study , we can assume , based on the composition of each material , that single bond presents a higher viscosity than prime & bond nt12,27 .
single bond contains 60 - 70 wt% of bis - gma in its composition ( table 1 ) , which can significantly increase its viscosity .
bis - gma is a very viscous substance because it has a high molecular weight , it has a large rigid section , and it is capable of hydrogen bonding to its neighbors due to the presence of the hydroxyl group and carbonyl oxygen11 .
more viscous adhesives do not wet well a substrate as do less viscous ones17 . also , the substrate chemical composition and the adhesive complex monomeric mixture influence respectively surface free energy and surface tension16 , consequently affecting wettability and the time required to spreading24 .
once the substrates had the same origin and composition , i.e. glass slides , for all groups , it can be inferred that the surfaces tensions of the adhesive systems used are different , providing more or less wettability , in compliance with other results5 .
surface treatments can modify both surface free energy and roughness of a solid16 increasing or decreasing adhesives wettability over it .
theoretically , different surface treatments create different surface free energies and roughness , and therefore promote distinct adhesive wettabilities . in this study we found that the untreated , sandblasted or etched surfaces allowed adhesives to spread at similar velocities , being the spreading velocity affected only when these surfaces were silanated .
indeed , silane application decreased the mean spreading velocity of the adhesives tested ( p < 0.05 ) .
as silane is a bi - functional coupling agent , it can attach with both inorganic ( glass slide ) and organic substrates ( adhesive ) .
thus , silane probably modified the surface free energy of the substrate , negatively influencing adhesives spreading velocities .
conversely to our belief , it should facilitate the wettability and do not raise difficulties to adhesive spreading , as was observed here . perhaps , at least , more time will be necessary for an adhesive to spread and properly wet a ceramic surface .
it can be improved when occurring over rougher surfaces because these surfaces present a larger contact area available for bonding22,23 . unlike this
, rougher surfaces may challenge a liquid wettability since they can entrap air inside of their own irregularities , reducing the total area available for bonding11 .
we can also hypothesize that both situations are prone to happen at the same time , leading to no roughness effect on bonding .
so , it is not surprising that some authors have not found any correlation between roughness and wettability2 .
our results corroborate those findings since we did not observe any correlation between roughness and spreading velocity , considering the surface treatment protocols adopted here and the limitations of this work .
nevertheless , apart from the roughness parameter to influence wettability and spreading , each surface treatment tested may have created , besides roughness , chemical modifications on the subsurface of the substrate , thereby providing dissimilar surface free energies of the glass slide .
it can be inferred since the external surface free energy of a solid is higher than the internal free energy3 , and , probably , the lower free energy of treated surface may have influenced on the spreading velocities more than roughness .
as expected , sandblasted surfaces were rougher than the other ones . whereas sandblasting created more roughness , the spreading velocity values observed for these rougher surfaces were not different from those found in the etched and unetched ones without silanization ( p > 0.05 ) , suggesting that all of them have similar wettabilities .
moreover , it has been suggested that if a surface is too much rough it can avoid an adequate adhesive spreading16 .
nevertheless , grooves and porosities found in sandblasted ceramics surfaces can not be considered the only factors responsible to worsen ceramic 's flexural resistance , as this property is highly dependent on the specific composition and microstructure of each material1 .
hence , sandblasting should not be recommended to increase wettability and adhesion , at least from the standpoint of an adherend / adhesive surface interaction .
. the lower roughness of the hf etched surfaces can be due to the formation of insoluble silica salts on the glass slide surface similar to what happens in ceramics6,9 .
the use of an ultrasonic bath for 1 minute probably did not remove these insoluble precipitates .
differences in ceramics microstructure and composition can affect the micromechanical retention created by etchant solutions13,15,19 , and this may explain the restrict roughness reached by hydrofluoric acid .
acid etching has a limited influence on the surface free energy of ceramics and it is necessary to silanate these etched surfaces to get adhesion improved20 .
silanization increases the adhesive strength of ceramics to dental tissues , regardless of the material composition or acid etching15 .
therefore , due to the inadequate surface characterization reached by hf in this study due to a similar roughness found in etched and unetched surfaces , from the standpoint of adhesive strength , it is suggested that silanization alone should be enough to improve adhesion8,14,19,26 .
silanization statistically decreased the roughness of sandblasted surfaces , but the same effect was not found in other groups .
we suggest that silane penetrated into the more pronounced irregularities created by sandblasting , minimizing their magnitude . however , silanization was not enough to reduce the roughness of sandblasted surfaces to the levels found in the non - sandblasted ones , confirming that sandblasting can create too much roughness on a glass surface .
nevertheless , even this not so pronounced " smoothing effect " of silanization can be capable to reinforce ceramics structure .
most researches on ceramic area have studied tensile strength21 or flexural strength after treatments and silanization . the explanation for the improvement in these mechanical properties after silanization can be related to two aspects , the possibility of silane to fill the irregularities created by surface treatments9,21 , and by its chemical adhesion with the substrate , i.e. adhesive / resinous cement / ceramic29 . in accordance with the hypotheses tested previously to this study and based on the results found here , we reject the null hypotheses 1 , 2 and 3 , i.e.
, there was a significant difference on the surface roughness obtained from the different surface treatments ; there was a significant difference in the spreading velocity of the adhesives tested and there was a significant difference in the spreading velocity of both adhesives over the surfaces submitted to different treatments .
we accept the null hypothesis 4 since no correlation between spreading velocity and surface roughness was found .
these findings suggest that more research is needed to understand the role of surface treatments on adhesion as well on the stability of dental porcelain , when current adhesive systems are employed .
within the limitations of this study , the real need to treat a surface ( e.g. , sandblasting , hf ) of a glass restorative substrate ( ceramic ) prior to adhesive procedures may be questioned , at least from the standpoint of wetting .
although surface treatments yielded different roughness , they did not provide differences in the spreading velocity of the simplified bonding systems studied .
silanization decreased bonding systems ' spreading velocities , so it may raise difficulties for an adhesive to properly wet a substrate , thus adversely affecting bonding .
 objectives : to determine the roughness of glass surfaces submitted to different treatments and to correlate it with the spreading velocity of two adhesive systems.materials and methods : glass slides were used as substrates to evaluate the spreading velocity of single bond and prime & bond nt adhesive systems . 
 six different surface treatments were compared : 1 ) no treatment ; 2 ) silanization ( sl ) ; 3 ) sandblasting ( sb ) ; 4 ) sb + sl ; 5 ) 10% hydrofluoric acid treatment ( hf ) ; 6 ) hf + sl . before and after treatments , surface roughness was measured by a profilometer ( ra , m ) . 
 drop volumes ( 10 l ) of the adhesive systems were deposited onto substrates with a micropipette to observe materials spreading during 30s . 
 data were expressed in mm / s as spreading velocity . 
 statistical significances among groups were analyzed using one - way and two - way - anova designs and the snk test.results:significant differences in spreading velocity were found between materials ( p < 0.001 ) and among treatments ( p < 0.001 ) . 
 silanization decreased the spreading velocity for both adhesives in comparison to groups where it was not performed ( p < 0.05 ) . 
 differences in roughness were found only for sb surfaces that were rougher than the others ( p < 0.05 ) . 
 silanization decreased the roughness of sb surfaces ( p < 0.05 ) . 
 linear regression did not indicate any correlation between spreading velocity and roughness ( r = 0.173).conclusions : although surface treatments yielded different roughness , they did not provide differences in the spreading velocity of the simplified bonding systems studied . 
 silanization decreased bonding systems ' spreading velocities . 
Objetivo:
Material and Mtodos:
Resultados:
Concluses:
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION