color and surface roughness are very important properties in aesthetics , characterizing 
 a smile .
since the introduction of 
 composites in 1960 , efforts have been made to increase the longevity of composite 
 restorations .
although some progress has been made , optical properties in this type of 
 materials need to be improved .
the color change of composites is multifactorial , being associated with intrinsic 
 discoloration and extrinsic staining of the material .
intrinsic factors involve changes 
 in the chemical stability of resin matrix and matrix / particles interface , and extrinsic 
 factors are related to absorption of staining solutions from exogenous sources related 
 to hygiene habits , food , and smoking .
composite structure and the characteristics of the inorganic fillers have a direct 
 impact on composite resin surface smoothness and susceptibility to extrinsic staining .
several studies have shown that 
 composite resins are susceptible to color alteration when exposed to staining solutions , 
 especially red wine , coffee , cola , tea and whisky .
furthermore , this 
 property depends on both water absorption of the composite and its hydrophilic resin 
 matrix to allow permeation of staining agents , thus resulting in greater color 
 changes .
today , the number of people using mouth rinse solutions for anti - microbial control has 
 increased not only because of professional recommendations , but also due to the capacity 
 of such materials to provide cooling sensation and to reduce halitosis .
mouth rinse solutions have various 
 components such as detergents , emulsifiers , organic acids , dyes and alcohol .
it is known 
 that composite resins exposed to ethanol exhibit lower microhardness values compared to 
 non - exposed materials . according to 
 sarret , et al.(2000 ) , alcohol acts 
 as a plasticizer of the polymeric matrix , making the material more ductile .
in addition , 
 ethanol can reduce bonding between resin matrix and inorganic fillers , which might 
 decrease erosion resistance and cause staining of resin matrix .
thus , the purpose of this study was to evaluate the effect of mouth rinse solutions on 
 color stability , surface roughness and microhardness of composite resins .
the null 
 hypothesis stated that mouth rinse solutions would not promote changes in the properties 
 of the studied composites .
two direct composite resins ( shade a3 ) currently indicated for esthetic anterior and 
 posterior restorations were used in the present study .
bis - gma : bisphenol a diglycidyl ether dimethacrylate ; bis - ema : ethoxylated 
 bisphenol a dimethacrylate , tegdma : triethylene glycol dimethacrylate ; udma : 
 urethane dimethacrylate fifty cylindrical test specimens ( 12 mm diameter x 2 mm thick ) of each composite were 
 made using a teflon matrix .
each material was inserted into the matrix in 2 
 increments and light - activated by a led device ( flashlite 1401 , discus dental , culver 
 city , ca , usa , light intensity 1100 mw / cm , wavelength in the range 
 between 460 and 480 nm ) , for 20 seconds , according to manufacturer 's recommendations . 
 the specimens were polished with 320 , 600 , 1200 and 2000-grit sandpapers .
the 
 thickness of every test specimen was checked with a digital caliper ( digimess , so 
 paulo , sp , brazil ) .
next , the test specimens were randomly separated into 5 groups 
 ( n=10 ) according to the mouth rinse solution in which they had been immersed ( figure 2 ) : group 1 - distilled water ( control ) ; 
 group 2 - plax classic ; group 3 - plax alcohol - free ; group 4 - periogard ; and group 5 
 - listerine cool mint . to simulate the use of mouth rinse solutions once a day during a period of 1 year , 

the test specimens were submitted to 12 cycles of 1-min immersion , then washed in 
 running water and immersed in distilled water for 29 min at 37c , during 30 days , 
 totaling 360 cycles . before immersion , color reading of the test specimens was performed according to the 
 cie ( commission internationale de l'eclairage ) l*a*b * system , against a white 
 background ( standard for 45/0 ; gardner laboratory inc . ,
bethesda , md , usa ) in a 
 reflection spectrophotometer ( pcb 6807 , byk gardner , geretsried , germany ) .
this 
 equipment is specific for color reading and has 30 led lamps with 10 different colors 
 arranged in a circle , which directs a light bundle at 45 with the material surface . 

this light bundle is reflected 0 back to the equipment , which captures and records 
 the l * , a * and b * values of each specimen .
the l * axes refers to the lightness 
 coordinate and its value ranges from zero ( black ) to 100 ( white ) . the axis a * and b * 
 are chromaticity coordinates in the red - green axis and the yellow - blue axis , 
 respectively .
positive a * values indicate a shift to red and negative values indicate 
 a shift to green .
similarly , positive b * values indicate the yellow color range and 
 negative values indicate the blue color range .
after immersion in mouth rinse solutions , specimens color was measured by the 
 spectrophotometer , as previously described .
based on the l * , a * , b * values , color 
 variation ( de ) was determined using the following equation : e=[(l*)+(a*)+(b * ) ] values of e3.3 were considered clinically unacceptable .
surface roughness ( ra ) and knoop microhardness of the test specimens were 
 performed before and after mouth rinse solution immersion .
surface roughness was 
 measured with a rugosimeter ( mitutoyo sj-201p , mitutoyo , tokyo , japan ) , cut - off - 
 0.25 mm , lc parameter - 1.25 , speed - 0.1 mm / s . the rugosimeter needle ( 10 
 m diameter )
was positioned over each test specimen , performing three readings in 
 different locations of the sample surface , after which , the mean roughness of the 
 test specimens were obtained .
surface roughness changes were calculated by the 
 differences between mean values obtained before and after immersion .
the knoop microhardness of the test specimens was measured ( shimadzu device , hmv 
 shimadzu , kyoto , japan ) in three different points , with a 10 n/15 s load .
after three 
 readings , the microhardness mean values of the test specimens were obtained . for 
 knoop microhardness calculation , the baseline mean values were subtracted from those 
 obtained after immersion . for each property ,
data obtained were subjected to two - way anova and the measurements 
 were compared by the bonferroni 's test .
two direct composite resins ( shade a3 ) currently indicated for esthetic anterior and 
 posterior restorations were used in the present study .
bis - gma : bisphenol a diglycidyl ether dimethacrylate ; bis - ema : ethoxylated 
 bisphenol a dimethacrylate , tegdma : triethylene glycol dimethacrylate ; udma : 
 urethane dimethacrylate fifty cylindrical test specimens ( 12 mm diameter x 2 mm thick ) of each composite were 
 made using a teflon matrix .
each material was inserted into the matrix in 2 
 increments and light - activated by a led device ( flashlite 1401 , discus dental , culver 
 city , ca , usa , light intensity 1100 mw / cm , wavelength in the range 
 between 460 and 480 nm ) , for 20 seconds , according to manufacturer 's recommendations . 
 the specimens were polished with 320 , 600 , 1200 and 2000-grit sandpapers .
the 
 thickness of every test specimen was checked with a digital caliper ( digimess , so 
 paulo , sp , brazil ) .
next , the test specimens were randomly separated into 5 groups 
 ( n=10 ) according to the mouth rinse solution in which they had been immersed ( figure 2 ) : group 1 - distilled water ( control ) ; 
 group 2 - plax classic ; group 3 - plax alcohol - free ; group 4 - periogard ; and group 5 
 - listerine cool mint . to simulate the use of mouth rinse solutions once a day during a period of 1 year , 

the test specimens were submitted to 12 cycles of 1-min immersion , then washed in 
 running water and immersed in distilled water for 29 min at 37c , during 30 days , 
 totaling 360 cycles .
before immersion , color reading of the test specimens was performed according to the 
 cie ( commission internationale de l'eclairage ) l*a*b * system , against a white 
 background ( standard for 45/0 ; gardner laboratory inc . ,
bethesda , md , usa ) in a 
 reflection spectrophotometer ( pcb 6807 , byk gardner , geretsried , germany ) .
this 
 equipment is specific for color reading and has 30 led lamps with 10 different colors 
 arranged in a circle , which directs a light bundle at 45 with the material surface . 

this light bundle is reflected 0 back to the equipment , which captures and records 
 the l * , a * and b * values of each specimen .
the l * axes refers to the lightness 
 coordinate and its value ranges from zero ( black ) to 100 ( white ) . the axis a * and b * 
 are chromaticity coordinates in the red - green axis and the yellow - blue axis , 
 respectively .
positive a * values indicate a shift to red and negative values indicate 
 a shift to green .
similarly , positive b * values indicate the yellow color range and 
 negative values indicate the blue color range . after immersion in mouth
rinse solutions , specimens color was measured by the 
 spectrophotometer , as previously described .
based on the l * , a * , b * values , color 
 variation ( de ) was determined using the following equation : e=[(l*)+(a*)+(b * ) ] values of e3.3 were considered clinically unacceptable .
surface roughness ( ra ) and knoop microhardness of the test specimens were 
 performed before and after mouth rinse solution immersion .
surface roughness was 
 measured with a rugosimeter ( mitutoyo sj-201p , mitutoyo , tokyo , japan ) , cut - off - 
 0.25 mm , lc parameter - 1.25 , speed - 0.1 mm / s .
the rugosimeter needle ( 10 
 m diameter ) was positioned over each test specimen , performing three readings in 
 different locations of the sample surface , after which , the mean roughness of the 
 test specimens were obtained .
surface roughness changes were calculated by the 
 differences between mean values obtained before and after immersion .
the knoop microhardness of the test specimens was measured ( shimadzu device , hmv 
 shimadzu , kyoto , japan ) in three different points , with a 10 n/15 s load .
after three 
 readings , the microhardness mean values of the test specimens were obtained . for 
 knoop microhardness calculation ,
for each property , data obtained were subjected to two - way anova and the measurements 
 were compared by the bonferroni 's test .
the mean values and standard deviations for color stability ( e ) changes are 
 presented in table 1 . none of the studied 
 composites exhibited color change with values above the clinically acceptable limit 
 ( e3.3 ) . with regard to 
 z250 , comparison of the effects of different mouth rinse solutions revealed a small 
 color change for specimens immersed in listerine , with statistically significant 
 difference compared with the other mouth rinse solutions ( p<0.05 )
when immersed 
 in plax classic solution , this composite exhibited an intermediate de value without 
 statistically significant difference compared to other mouth rinse solutions 
 ( p>0.05 ) .
with regard to z350 , the highest de change was observed for plax 
 alcohol - free solution , with statistically significant difference compared with the 
 other solutions ( p>0.05 ) , except for listerine . comparing the composites to each 
 other ,
it was observed statistically significant difference ( p<0.05 ) for the test 
 specimens immersed in distilled water ( control ) , with both plax classic and periogard 
 solutions allowing smaller color changes for z350 .
means ( standard deviations ) for e values ( 2-way anova , bonferroni 's 
 test ; p<0.05 ) different lowercase letters in lines and uppercase letters in columns 
 indicate statistically significant difference .
the mean values and standard deviations for surface roughness ( ra ) changes 
 are presented in table 2 . for both 
 composites ,
the greatest change in ra occurred when the samples were 
 immersed in listerine solution , with statistically significant difference compared 
 with plax alcohol - free ( p<0.05 ) .
when compared to each other , 
 z250 and z350 , showed no statistically significant difference 
 ( p>0.05 ) regarding any studied mouth rinse solution .
means ( standard deviations ) for ra ( % ) values ( 2-way anova , 
 bonferroni 's test ; p<0.05 ) different lowercase letters in lines and uppercase letters in columns 
 indicate statistically significant difference .
the mean values and standard deviations for knoop microhardness changes are presented 
 in table 3 .
when compared to each other , z250 
 and z350 showed no statistically significant difference ( p>0.05 ) 
 regarding any studied mouth rinse solution .
immersion of z350 in plax alcohol - free 
 solution resulted in greater decrease of microhardness values , with statistically 
 significant difference in relation to the other mouth rinse solutions 
 ( p<0.05 ) .
means ( standard deviations ) for knoop microhardness ( % ) values ( 2-way anova , 
 bonferroni 's test ; p<0.05 ) different lowercase letters in lines and uppercase letters in columns 
 indicate statistically significant difference .
the mean values and standard deviations for color stability ( e ) changes are 
 presented in table 1 . none of the studied 
 composites exhibited color change with values above the clinically acceptable limit 
 ( e3.3 ) . with regard to 
 z250 , comparison of the effects of different mouth rinse solutions revealed a small 
 color change for specimens immersed in listerine , with statistically significant 
 difference compared with the other mouth rinse solutions ( p<0.05 )
when immersed 
 in plax classic solution , this composite exhibited an intermediate de value without 
 statistically significant difference compared to other mouth rinse solutions 
 ( p>0.05 ) .
with regard to z350 , the highest de change was observed for plax 
 alcohol - free solution , with statistically significant difference compared with the 
 other solutions ( p>0.05 ) , except for listerine . comparing the composites to each 
 other ,
it was observed statistically significant difference ( p<0.05 ) for the test 
 specimens immersed in distilled water ( control ) , with both plax classic and periogard 
 solutions allowing smaller color changes for z350 .
means ( standard deviations ) for e values ( 2-way anova , bonferroni 's 
 test ; p<0.05 ) different lowercase letters in lines and uppercase letters in columns 
 indicate statistically significant difference .
the mean values and standard deviations for surface roughness ( ra ) changes 
 are presented in table 2 . for both 
 composites ,
the greatest change in ra occurred when the samples were 
 immersed in listerine solution , with statistically significant difference compared 
 with plax alcohol - free ( p<0.05 ) .
when compared to each other , 
 z250 and z350 , showed no statistically significant difference 
 ( p>0.05 ) regarding any studied mouth rinse solution .
means ( standard deviations ) for ra ( % ) values ( 2-way anova , 
 bonferroni 's test ; p<0.05 ) different lowercase letters in lines and uppercase letters in columns 
 indicate statistically significant difference .
the mean values and standard deviations for knoop microhardness changes are presented 
 in table 3 .
when compared to each other , z250 
 and z350 showed no statistically significant difference ( p>0.05 ) 
 regarding any studied mouth rinse solution .
immersion of z350 in plax alcohol - free 
 solution resulted in greater decrease of microhardness values , with statistically 
 significant difference in relation to the other mouth rinse solutions 
 ( p<0.05 ) .
means ( standard deviations ) for knoop microhardness ( % ) values ( 2-way anova , 
 bonferroni 's test ; p<0.05 ) different lowercase letters in lines and uppercase letters in columns 
 indicate statistically significant difference .
the variability in our results was consistent with other studies , which showed that 
 several factors , including composite resin type , mouth rinse solution and immersion 
 cycle , had a significant influence on color stability , surface roughness and 
 microhardness of composites . 

the methodology used in the present 
 study is according to previous studies that used spectrophotometry and the cie l*a*b * 
 coordinates system .
the cie l*a*b * system was chosen to evaluate color 
 variation ( de ) because it is appropriate for small color changes determination and have 
 advantages such as repeatability , sensitivity and objectivity .
several authors have reported that e values ranging from 1 to 3 are perceptible to the 
 naked eye and e values greater than 
 3.3 are clinically unacceptable . 

considering these concepts ; the composite resins tested in the present study 
 demonstrated acceptable color stability when stored in the different types of mouth 
 rinse solutions ( table 1 ) .
the affinity of the resin matrix for stains is modulated by its conversion degree and by 
 some physical properties , such as water sorption .
it has been reported that 
 water uptake in bis - gma based composite resins increased from 3 to 6% , as the proportion 
 of tegdma increased from 0 to 1% . 

udma seems to be more stain resistant than bis - gma , and under normal curing conditions , udma based composite resins 
 presented lower water sorption and higher color stability than other dimethacrylates in 
 their resin matrix , which could be observed in the present study .
moreover , it is important that the composite resin presents uniform filler particle 
 distribution in the polymer network to minimize the formation of filler - rich and 
 filler - depleted areas within the composites .
this is especially important regarding the 
 performance of composites in aqueous environments , such as mouth rinse solutions , since 
 voids or nonbonding spaces at the filler / matrix interface may increase the water 
 sorption of composites .
nanocomposites correspond to a class of new materials with nanoscale inorganic filler 
 particles dispersed within the resinous matrix . in comparison with microhybrid composites ,
these materials have 
 been reported to have improved properties , such as , elasticity modulus , mechanical 
 strength and color stability .
furthermore , these improvements are achieved at low 
 concentrations of the inorganic filler particles .
this fact contrasts strongly with 
 conventional filled composites , which generally require high loadings within the range 
 of 60% .
this is an important factor in aesthetic maintenance of 
 non - particulate composites , since filler particles are responsible for spreading the 
 light , which in turn , provides the opacity of the restorative resin materials .
the 
 larger the filler particle size the greater the light spread , and consequently , the 
 greater the opacity .
the opacity of 
 composites increases as the difference between the refraction indexes of resinous matrix 
 and filler particles also increases . 

in addition , the smaller the filler particle , the smaller the amount of water absorbed 
 by the polymer network , which results in lower degradation of the interface 
 matrix / particle , and consequently , lower color change .
the z250 contains filler particles with average size of 
 0.6 m , while z350 contains filler particles ranging from 5 to 20 nm , which could 
 explain the greater color stability for z350 .
also , according to kawaguchi , et al.(1994 ) , microhybrid composites present a lower 
 coefficient of light transmission due to the various sizes of their particles , which 
 contributed to the higher values of e for z250 . according to villalta ,
et al.30 
 ( 2006 ) , the low ph and alcohol concentration of solutions affect the 
 surface roughness of composite resins and cause staining . nevertheless , the composite 
 z350 presented statistically significant difference regarding color stability , surface 
 roughness and microhardness values when the composite was immersed in the alcohol - free 
 mouth rinse solution ( plax alcohol - free ) , thus contradicting the results of a previous 
 study
( 2011 ) demonstrated that 
 despite the absence of alcohol , plax alcohol - free has phosphoric acid in its 
 composition , which might alter the polymer matrix of composites by catalysis of the 
 ester groups present in the dimethacrylate monomers .
the hydrolysis of the ester groups 
 forms alcohol and carboxylic acid molecules , which accelerate polymer network 
 degradation by the decrease of ph inside the composite matrix .
the 
 degradation of the polymer network leads to a phenomenon called " plasticization " , which 
 decreases microhardness values in composites . according to the methodology used in the present study ,
the negative values regarding 
 microhardness represent a smoothening of the resin matrix , and positive values , 
 hardening . despite the great decrease in the composite microhardness ( -25.73 ) ,
the 
 surface roughness improved when compared to the pre - immersion values , except when the 
 composite was immersed in the plax alcohol - free solution .
the same result was observed 
 for z250 , since a significant change in surface roughness was found after immersion into 
 the same mouth rinse solution .
it is worth emphasizing , however , that there exists a 
 critical value regarding surface roughness change ( ra0.2 m ) . according to 
 bollen , et al.(1997 ) ,
another critical value for 
 ra is 0.3 m , which can be detected when the patient 's lips or tongue 
 enters in contact with the restorative material , causing discomfort .
none of the studied composites showed 
 values for surface roughness change above the critical limits , irrespective of the type 
 of mouth rinse solution used .
asmussen ( 1984 ) reported that mouth 
 rinse solutions with high alcohol content might soften the composite resin , especially 
 bis - gma - based composites .
( 1997 ) showed that regardless of the alcohol concentration , both 
 alcohol - containing and alcohol - free mouth rinse solutions could affect the properties of 
 composite resins
. immersed of z350 in listerine , the mouth rinse solution with the 
 highest alcohol concentration ( 30% ) , resulted in decrease in microhardness values , 
 though with no significant difference from the other mouth rinse solutions . as for z250 , 
 the results were the opposite ; there was an increase in the microhardness values when 
 immersed in listerine and a decrease when immersed in plax alcohol - free solution , with 
 statistically significant difference .
these results suggest that changes in the 
 microhardness of composites do not depend on mouth rinse 's ethanol 
 concentration .
z350 showed significant 
 changes when immersed in listerine and plax alcohol - free solutions , both having entirely 
 different concentrations of ethanol . 

however , this fact could be explained , once again , by the presence of phosphoric acid in 
 plax alcohol - free composition .
studies have reported the release of by - products from 
 polymer network degradation , such as methacrylic acid , formaldehyde and specific 
 methacrylate molecules , which are capable of promoting color change in 
 composites . on the other hand , z250 had greater color change when immersed in listerine compared to 
 the other solutions , unlike celik , et al .
( 2008 ) , who found no color change in the composites immersed in the 
 same mouth rinse solution , despite the high ethanol concentration .
clinically , the effect of mouth rinse solutions on restorative materials can be modified 
 by several factors that were not replicated in this in vitro study . 
 among these factors ,
saliva could dilute or buffer ph of mouth rinse solutions , thus 
 reducing the effect of resinous matrix plasticization and forming a pellicle that could have a protective 
 effect on the composite surface , thus , decreasing material staining .
based on such factors , further 
 in vivo studies are needed to determine the effects of mouth rinse 
 solutions on these properties of composites .
the results of the present study allow us to conclude that the changes observed in the 
 composites depended on the material itself rather than the mouth rinse solution 
 used .
 objectivethe purpose of this study was to evaluate the effect of mouth rinse solutions on 
 color stability , surface roughness and microhardness of two composite resins . 
 material and methods fifty test specimens of each composite ( filtek z250 and z350 ; 3 m espe ) were made 
 using a teflon matrix ( 12x2 mm ) . 
 color , surface roughness and knoop microhardness 
 baseline measurements of each specimen were made and specimens ( n=10 ) were 
 immersed in 5 mouth rinse solutions : g1 : distilled water ( control ) , g2 : plax 
 classic , g3 : plax alcohol - free ; g4 : periogard , and g5 : listerine . 
 final 
 measurements of color , roughness and microhardness were performed and the results 
 submitted to statistical analysis ( 2-way anova , bonferroni 's test ; p<0.05 ) . 
 results the most significant color change was observed for z250 when immersed in 
 listerine ( p<0.05 ) . 
 z350 showed greater color change when immersed in plax 
 alcohol - free ( p<0.05 ) , but with no significant difference for listerine 
 ( p>0.05 ) . 
 with regard to roughness , both composites showed significant changes 
 when immersed in listerine in comparison with plax alcohol - free ( p<0.05 ) . 
 
 microhardness of z350 was shown to be significantly changed when the composite was 
 immersed in plax alcohol - free ( p<0.05 ) . 
 conclusion composite changes depended on the material itself rather than the mouth rinse 
 solution used . 
INTRODUCTION
MATERIAL AND METHODS
Samples preparation
Color stability
Surface roughness and Knoop microhardness
Statistical analysis
RESULTS
Color stability
Surface roughness
Knoop microhardness
DISCUSSION
CONCLUSIONS