role of food acids as the main cause of erosion has been documented in numerous studies .
dentin hypersensitivity is usually associated with cervical erosion and has been suggested as a direct clinical outcome of erosion . clinical pattern of erosion includes porosities in dentin surrounded by a prominent enamel margin .
various studies have evaluated the role of fluoride - containing solutions and varnishes and casein , calcium and phosphate - containing compounds ( casein phosphopeptide - amorphous calcium phosphate [ cpp - acp ] ) in the prevention and reduction of erosive wear .
application of ionized fluoride , i.e. , sodium fluoride , amine fluoride or stannous fluoride on tooth surfaces results in deposition of calcium fluoride ( caf2 ) on the enamel surface . under neutral conditions ,
caf2 deposition is facilitated by increasing the concentration of fluoride ion , longer exposure time , and lowering the ph of the solution .
the fluoride ions released from caf2 can incorporate into the dental hard tissue and result in its further stability , hardness and increased abrasion resistance . when enamel and dentin are exposed to fluoride ions , the calcium and phosphate present in tooth structure form fluorapatite crystals with these ions .
cpp - acp complex provides optimal concentrations of calcium and phosphate ions for enhancement of enamel remineralization .
tooth mousse ( tm ) is a water - based sugar - free cream that contains cpp - acp . when applied , it maintains optimal concentrations of calcium and phosphate ions on enamel surfaces to enhance remineralization . in vitro studies
have demonstrated that cpp - acp can be absorbed by the salivary pellicle and dental plaque .
thus , a calcium - rich reservoir is formed that can facilitate remineralization . until date , no study has compared the efficacy of cpp - acp paste and sodium fluoride mouthwash for prevention of erosive wear .
considering the popularity of sodium fluoride mouthwash among the iranian population and the recent introduction of tm to the iranian market , the present study was conducted aiming at comparing the efficacy of 0.2% sodium fluoride mouthwash and cpp - acp paste for prevention of dentin erosion in human teeth . in this study ,
various researchers have shown that profilometry is a highly accurate method for the measurement of surface loss ( > 0.4 m ) .
this in vitro experimental study was conducted on 36 sound human premolar teeth ( with no caries or fracture ) that had been extracted as the result of periodontal disease or for orthodontic treatment .
calculation of sample size in each group was done using ncss software ( ncss 2007 .
the surfaces were then rinsed with deionized water and placed in ethylenediaminetetraacetic acid 17% solution for 1 min for smear layer removal .
afterwards , half the tooth surfaces were covered with adhesive tape and samples were then randomly divided into three groups of 12 each . for higher precision and comfort in the next steps ( pretreatment and erosion phases ) ,
three clean and transparent glasses were prepared and a circle was drawn on their internal surfaces in a height higher than the mid - height of the longest tooth .
the drawn circle was covered with adhesive tape to prevent wiping off or fading when in contact with acid and mouthwash . in the next step ,
the samples were glued to the external surface of glasses ( each group on one glass ) in a way that the covered halves of the teeth were placed above the drawn circle and their remaining halves were located below it . in the next steps , these glasses were placed in dishes containing acid or mouthwash .
the amount of acid and mouthwash was regulated in a way that the surface of acid or mouthwash was in alignment with the drawn circle . by doing so
, we made sure that the upper halves of teeth were not exposed to acid or mouthwash and were safely protected from the effects of these solutions .
in the first group , samples received pretreatment with cpp - acp paste ( tm , gc , japan ) according to the manufacturer 's instructions .
tm paste was applied on samples 4 times a day ( 5 min each time ) for 5 days . after each phase of pretreatment
, the teeth were irrigated with deionized water and stored in artificial saliva ( ph = 7.3 ) until the next phase .
deionized water , carboxymethyl cellulose , mgcl2 , kcl , cacl2 , nacl , k2hpo4 , and sorbitol were the constituents of artificial saliva .
this solution was prepared by the iran polymer and petrochemical research center upon the author 's request . in the second group , samples were pretreated with 0.2% sodium fluoride mouthwash ( behsa , iran ) .
samples were placed in the mouthwash 4 times a day ( 1 min each time ) for 5 days according to the manufacturer 's instructions .
after each phase of pretreatment , the teeth were irrigated with deionized water and stored in artificial saliva .
after completion of pretreatment phase , the teeth in all three groups were exposed to acid under similar conditions .
the samples were placed in a glass of coca - cola 4 times a day ( 2 min each time ) for 3 days . as mentioned earlier , the surface of drink was in alignment with the drawn circle to prevent penetration of drink under the adhesive tape .
after each phase , samples were rinsed with deionized water and stored in artificial saliva until the next phase of the test .
furthermore , in order to have a stable rest for profilometry each group of teeth were glued on a piece of cardboard . in the next phase ,
the amount of surface loss in samples was measured by a profilometer ( emd-1500 - 311 , mahr federal inc .
the output of profilometer is the greatest difference in surface area scanned by the stylus which is shown as ymax . for each tooth
, profilometry was performed 3 times ( for the protected surface , for the eroded surface and for a total surface area ) and three output data were obtained .
finally , the protected and eroded surfaces in each tooth were compared with each other .
values measured by the profilometer data were analyzed using spss version 16 software ( spss inc , chicago , il , usa ) .
one - way anova was used for comparison of erosion rate and surface changes in the three understudy groups .
the surfaces were then rinsed with deionized water and placed in ethylenediaminetetraacetic acid 17% solution for 1 min for smear layer removal .
afterwards , half the tooth surfaces were covered with adhesive tape and samples were then randomly divided into three groups of 12 each . for higher precision and comfort in the next steps ( pretreatment and erosion phases ) ,
three clean and transparent glasses were prepared and a circle was drawn on their internal surfaces in a height higher than the mid - height of the longest tooth . the drawn circle was covered with adhesive tape to prevent wiping off or fading when in contact with acid and mouthwash . in the next step ,
the samples were glued to the external surface of glasses ( each group on one glass ) in a way that the covered halves of the teeth were placed above the drawn circle and their remaining halves were located below it . in the next steps , these glasses were placed in dishes containing acid or mouthwash .
the amount of acid and mouthwash was regulated in a way that the surface of acid or mouthwash was in alignment with the drawn circle . by doing so
, we made sure that the upper halves of teeth were not exposed to acid or mouthwash and were safely protected from the effects of these solutions .
two groups received pretreatment before placing in acid solution . in the first group , samples received pretreatment with cpp - acp paste ( tm , gc , japan ) according to the manufacturer 's instructions .
tm paste was applied on samples 4 times a day ( 5 min each time ) for 5 days . after each phase of pretreatment
, the teeth were irrigated with deionized water and stored in artificial saliva ( ph = 7.3 ) until the next phase .
deionized water , carboxymethyl cellulose , mgcl2 , kcl , cacl2 , nacl , k2hpo4 , and sorbitol were the constituents of artificial saliva .
this solution was prepared by the iran polymer and petrochemical research center upon the author 's request . in the second group , samples were pretreated with 0.2% sodium fluoride mouthwash ( behsa , iran ) .
samples were placed in the mouthwash 4 times a day ( 1 min each time ) for 5 days according to the manufacturer 's instructions .
after each phase of pretreatment , the teeth were irrigated with deionized water and stored in artificial saliva .
after completion of pretreatment phase , the teeth in all three groups were exposed to acid under similar conditions .
the samples were placed in a glass of coca - cola 4 times a day ( 2 min each time ) for 3 days . as mentioned earlier , the surface of drink was in alignment with the drawn circle to prevent penetration of drink under the adhesive tape .
after each phase , samples were rinsed with deionized water and stored in artificial saliva until the next phase of the test .
furthermore , in order to have a stable rest for profilometry each group of teeth were glued on a piece of cardboard .
in the next phase , the amount of surface loss in samples was measured by a profilometer ( emd-1500 - 311 , mahr federal inc . , germany ) .
the output of profilometer is the greatest difference in surface area scanned by the stylus which is shown as ymax . for each tooth
, profilometry was performed 3 times ( for the protected surface , for the eroded surface and for a total surface area ) and three output data were obtained .
finally , the protected and eroded surfaces in each tooth were compared with each other .
data were analyzed using spss version 16 software ( spss inc , chicago , il , usa ) .
one - way anova was used for comparison of erosion rate and surface changes in the three understudy groups .
table 1 shows the number of samples and statistical data regarding ymax for the protected and eroded surfaces , the total ymax and the surface loss . since , the whole tooth had similar surface roughness before exposure to acid , the surface loss or amount of erosion was calculated by subtracting ymax of the protected area from the total ymax .
this rate was 2.24  2.4 m in the paste pretreatment and 1.14  0.81 m in the mouthwash group , respectively .
test results of the three understudy groups anova failed to find a significant difference in mean surface roughness of protected surfaces between the three groups ( p = 0.051 ) .
furthermore , no significant difference was detected in mean surface roughness of eroded surfaces after exposure to acid between the three groups ( p = 0.052 ) .
comparison of mean total ymax and mean surface loss revealed a significant difference between the three groups ( p < 0.05 ) .
comparison of mean total ymax between the three groups showed no significant difference between the paste and the mouthwash groups ( p = 0.098 ) .
the paste and the control groups did not have a statistically significant difference in this respect either ( p = 0.853 ) . however , the difference between the mouthwash and the control group in this regard was statistically significant ( p < 0.05 ) .
comparison of mean surface loss between the three groups revealed no statistically significant difference between the paste and the mouthwash groups ( p = 0.284 ) .
the paste and the control groups did not have a statistically significant difference in this regard either ( p = 0.094 ) . however , the difference between the mouthwash and the control group was statistically significant ( p < 0.05 ) .
figure 2 shows ymax values for the protected surfaces of the three groups . error bar of mean and 95% confidence interval of ymax for protected surfaces in the three groups of tooth mousse , mouthwash , and control figure 3 shows ymax values for surfaces exposed to acid
. error bar of mean and 95% confidence interval of ymax for eroded surfaces in the three groups of tooth mousse , mouthwash , and control total ymax values are demonstrated in figure 4 .
the ymax values are obtained when diamond stylus is moved vertically in contact with the protected and eroded tooth surfaces and then moved laterally across them for a specified distance and specified contact force .
error bar of mean and 95% confidence interval of total ymax for the three groups error bar of mean and 95% confidence interval of surface loss in the three groups
dentin hypersensitivity is among the direct outcomes of erosion that may occur in clean tooth surfaces .
acid reflux and acidic foods and beverages can dissolve the smear layer and expose dentinal tubules to the oral cavity resulting in aggravation of dentin hypersensitivity .
consumption of acidic foods and beverages play a significant role in occurrence of acid erosion in teeth . considering the growing consumption of soft drinks and
increased prevalence of dentin hypersensitivity among patients , the present study was conducted aiming at evaluating the role of preventive factors in prevention of erosion due to the consumption of coca - cola which is a popular drink worldwide .
the effectiveness of fluoride in toothpastes and mouthwashes is mainly because of strengthening the tooth surface against dissolution .
studies conducted on caries have shown that fluoride supplementation in the form of mouthwash increases the concentration of fluoride ion in the mouth which subsequently results in strengthening of teeth surfaces .
topical application of fluoride compounds leave behind a considerable amount of fluoride on tooth surfaces due to the porosities and water content of dentin . in deeper dentin layers , high fluoride concentrations act as a fluoride reservoir .
various studies have compared different fluoride - containing solutions and varnishes , fluoride mouthwashes with the different compositions and fluoride products in combination with other preventive materials .
others have evaluated the effect of increased concentration of sodium fluoride and the efficacy of fluoride compounds at various phs for prevention of erosion .
furthermore , it has been shown that calcium - containing compounds are capable of preventing erosive wear .
cpp - acp complex provides super - saturated concentrations of calcium and phosphate ions that prevent demineralization by providing a rich source of neutral ion pair ( capo4 ) and enhance the formation of hydroxyapatite crystals in demineralized lesions .
however , it has been revealed that cpp - acp remineralizes the enamel surface eroded as the result of acid exposure and increases its hardness .
many compounds other than cpp - acp are involved including glycerol , xylitol , propylene glycol , water , metal oxides , and hydroxybenzoates .
glycerol has been suggested to play a major role in the efficacy of tm for reduction of erosive wear of enamel and dentin due to its lubricating effect .
rees et al . , in their study compared the efficacy of tm ( containing cpp - acp ) and pronamel toothpaste for erosion prevention
taleb et al . , compared cpp - acp and fluoride gel in remineralization of demineralized human enamel surfaces .
some other studies assessed the effect of cpp - acp on prevention of erosive enamel and dentin wear and demineralization .
ymax value for protected surfaces from the total ymax was calculated , since ymax of protected surfaces was not significantly different between the three groups .
the results of this study revealed that both cpp - acp paste and sodium fluoride mouthwash were capable of reducing erosion which is in accord with the findings of wiegand et al .
, magalhes et al . , rees et al . , and ranjitkar et al .
, comparison of means showed that the rate of erosion ( surface loss ) in the control group was higher than the tm and mouthwash groups .
furthermore , the level of erosion in the tooth mouse group was greater than the mouthwash group .
thus , the efficacy of mouthwash for prevention of erosion was greater than that of tm .
paired comparison of groups revealed that although the rate of erosion ( surface loss ) in the cpp - acp group was lower than the control and higher than the mouthwash groups , none of these differences were statistically meaningful .
in contrast , rate of erosion ( surface loss ) in the mouthwash group was significantly lower than the control group which was in agreement with the findings of hamba et al . , they showed that sodium fluoride and cpp - acpf paste were more effective than cpp - acp for inhibition of enamel demineralization .
more recently many valuable articles are published regarding effect of cpp - acp on enamel by shetty et al . in 2014 , somasundaram et al . in 2013 , vashisht et al . in 2013 , and patil et al . in 2013 , and different results have been obtained , which all show that cpp with fluoride is a promising material for remineralization of enamel subsurface lesions and it means that still more studies have to be done to evaluate exact protective effect of cpp - acp .
this study showed that using mouthwash is an effective method for prevention of erosion in at - risk patients .
sodium fluoride mouthwash provides protection against caries and prevents erosive tooth wear by strengthening the enamel surface .
 aim : the purpose was to compare the effect of 0.2% sodium fluoride mouthwash and casein phosphopeptide - amorphous calcium phosphate paste on prevention of dentin erosion.materials and methods : buccal surfaces of 36 sound premolar teeth were ground flat and polished with abrasive discs . 
 half the polished surfaces were covered with tape to maintain a reference surface . 
 samples were randomly allocated into three groups . 
 group a was pretreated with tooth mousse ( tm ) 4 times a day for 5 days . 
 group b was pretreated with 0.2% sodium fluoride mouthwash 4 times a day for 5 days . 
 group c was considered as the control group with no pretreatment . in the next step , 
 the samples were exposed to coca - cola 4 times a day for 3 days . 
 after each erosive cycle , the samples were rinsed with deionized water and stored in artificial saliva . 
 the surface loss was determined using profilometry.results:the erosion in both groups a and b was less than the control group . 
 the surface loss in mouthwash group was significantly lower than in the control group . 
 erosion in tm group was more than the mouthwash group and less than the control group.conclusion:sodium fluoride mouthwash is more effective for prevention of dentin erosion . 
INTRODUCTION
MATERIALS AND METHODS
Preparation of samples
Pretreatment
Exposing the teeth to acid
Profilometry
Statistical analysis
RESULTS
DISCUSSION
CONCLUSION