dental caries is one of the causes of tooth loss for all human beings across age and gender .
numerous studies have been carried out , which have helped to increase our knowledge of dental caries and reduce the prevalence of dental caries . however , according to the world oral health report , dental caries still remains a major dental disease .
the caries process is well understood as a process of alternating demineralization and remineralization of tooth mineral ( featherstone 1999 ) .
the major shortcoming of currently available anti - caries products is the fact that their ability to remineralize enamel is limited by the low concentration of calcium and phosphate ions available in saliva .
this has led to the research of many new materials that can provide essential elements for remineralization .
some of them are bioactive glass ( bag ) , casein phosphopeptide - amorphous calcium phosphate ( cpp - acp ) .
bag is an unique material has numerous novel features ; the most important feature is its ability to act as a biomimetic mineralizer , matching the body 's own mineralizing traits .
cpp - acp is also one of the novel calcium phosphate remineralization technology , that shows to promote remineralization of enamel subsurface lesions in various in - vitro and in - vivo studies . in - vitro ph - cycling technique
was introduced , over 20 year ago , to study the effect of caries - preventive regimens and treatments .
many of the researchers have utilized and modified this ph - cycling model to suit their own studies to test different caries - preventive agents .
hence the aim of this study was to evaluate and compare the remineralization potential of bag and cpp - acp on early enamel carious lesion .
the null hypothesis for the present study was that there is no significant difference in the mean microhardness values of the two groups .
a total of 30 healthy human premolars , which were extracted for orthodontic purposes , were collected .
teeth were sectioned 1 mm below the cemento - enamel junction with a slow speed diamond disc .
the roots were discarded and the crowns were used for the study . to remove variability in samples , 200 m of surface enamel was removed from the buccal surface of all teeth with help of 600 grit abrasive paper and confirmed with digital caliper .
a 4 mm  4 mm working window was marked on the buccal surfaces of all the samples .
group a : bag containing dentifrice ( shy - nm ; group pharmaceuticals ; india ) and group b : cpp - acp ( gc tooth mousse ; recaldent ; gccorp ; japan ) containing dentifrice .
the area of the crown other than the working window was covered with nail varnish .
b - smh was checked with vicker 's microhardness testing machine ( vmt ) for all the tooth samples in the area of the working window .
the indentations were made with vmt at the rate of 25 gram load for 5 seconds .
the average microhardness of the specimen was determined from 3 indentations to avoid any discrepancy .
the buffered de-/re - mineralizing solutions were prepared using analytical grade chemicals and deionized water .
the demineralizing solution contained 2.2 mm calcium chloride , 2.2 mm sodium phosphate , and 0.05 m acetic acid ; the ph was adjusted with 1 m potassium hydroxide to 4.4 .
the remineralizing solution , which contained 1.5 mm calcium chloride , 0.9 mm sodium phosphate , and 0.15 m potassium chloride , had a ph of 7.0 .
samples were kept in demineralizing solution for 96 h to produce the artificial carious lesion in the enamel .
d - smh was checked with vmt , similarly as done for b - smh .
dentifrice supernatants were prepared by suspending 12 g of the respective dentifrice in 36-ml deionized water to create a 1:3 dilution .
the suspensions were thoroughly stirred with a stirring rod and mechanically agitated by means of a vortex mixer for 1 min .
the suspensions were then centrifuged at 3500 rpm for 20 min at room temperature , once daily before starting the ph - cycling .
the specimens were placed in the ph - cycling system on a cylindrical beaker for 10 days .
each cycle involved 3 h of demineralization twice a day with a 2 h immersion in a remineralizing solution in between [ figure 1 ] .
a 1-min treatment with a toothpaste solution of 3:1 deionized water to toothpaste , after centrifugation ( 5 ml / section ) , was given before the first demineralizing cycle and both before and after the second demineralizing cycle and sections were placed in a remineralizing solution overnight .
r - smh was checked with vmt , similarly as done for b - smh .
statistical analysis of data were conducted using anova and multiple comparisons within groups was done using bonferroni method ( post - hoc tests ) the decision criterion was to reject the null hypothesis if the p < 0.05 .
if there was a significant difference between the groups , multiple comparisons ( post - hoc test ) using bonferroni test was carried out .
b - smh was checked with vicker 's microhardness testing machine ( vmt ) for all the tooth samples in the area of the working window .
the indentations were made with vmt at the rate of 25 gram load for 5 seconds .
the average microhardness of the specimen was determined from 3 indentations to avoid any discrepancy .
the buffered de-/re - mineralizing solutions were prepared using analytical grade chemicals and deionized water .
the demineralizing solution contained 2.2 mm calcium chloride , 2.2 mm sodium phosphate , and 0.05 m acetic acid ; the ph was adjusted with 1 m potassium hydroxide to 4.4 .
the remineralizing solution , which contained 1.5 mm calcium chloride , 0.9 mm sodium phosphate , and 0.15 m potassium chloride , had a ph of 7.0 .
samples were kept in demineralizing solution for 96 h to produce the artificial carious lesion in the enamel .
d - smh was checked with vmt , similarly as done for b - smh .
dentifrice supernatants were prepared by suspending 12 g of the respective dentifrice in 36-ml deionized water to create a 1:3 dilution .
the suspensions were thoroughly stirred with a stirring rod and mechanically agitated by means of a vortex mixer for 1 min .
the suspensions were then centrifuged at 3500 rpm for 20 min at room temperature , once daily before starting the ph - cycling .
the specimens were placed in the ph - cycling system on a cylindrical beaker for 10 days .
each cycle involved 3 h of demineralization twice a day with a 2 h immersion in a remineralizing solution in between [ figure 1 ] .
a 1-min treatment with a toothpaste solution of 3:1 deionized water to toothpaste , after centrifugation ( 5 ml / section ) , was given before the first demineralizing cycle and both before and after the second demineralizing cycle and sections were placed in a remineralizing solution overnight .
r - smh was checked with vmt , similarly as done for b - smh .
statistical analysis of data were conducted using anova and multiple comparisons within groups was done using bonferroni method ( post - hoc tests ) the decision criterion was to reject the null hypothesis if the p < 0.05 .
if there was a significant difference between the groups , multiple comparisons ( post - hoc test ) using bonferroni test was carried out .
table 1 gives us the results of comparison of microhardness within each group , from anova and the p value .
mean microhardness in group a was found to be 385.93 at baseline , 300.40 after demineralization and 371.67 after remineralization . while in group b mean microhardness was found to be 385.73 at baseline , 314.73 after demineralization and 357.07 after remineralization .
these mean values for group a and group b were found to be statistically significant from baseline to after demineralization ( p < 0.001 * * ) as well as from after demineralization to after remineralization ( p < 0.001 * * ) .
mean microhardness within the groups table 2 gives us the results of comparison of microhardness between the group a and group b at different phases of the study .
no significant difference in mean microhardness was observed between both groups at baseline ( p > 0.05 ) and after demineralization ( p > 0.05 ) .
this indicates that the tooth samples were demineralized to almost the same level of hardness after demineralization , hence giving non - significant result on statistical analysis .
mean microhardness between the groups however , the difference in mean microhardness between the groups after remineralization , was found to be statistically significant after remineralization ( p < 0.05 ) , indicating changes in the mineralization of the tooth samples .
despite of major advances in the field of cariology , dental caries still remains a major problem affecting human population across the globe .
however caries process is now well - understood ; much of it has been described extensively in the dental literature .
early enamel carious lesion appears white because the normal translucency of the enamel is lost .
even though initial enamel lesions have intact surfaces , they have a low mineral content at the surface layer when compared to sound enamel ; thus showing a lower hardness value at the surface than for sound enamel tissue . when there is acid attack on the tooth surface , the acids lowers the surface ph and diffuse through the plaque , which causes loss of minerals from the enamel and dentine .
this mineral loss compromises the mechanical structure of the tooth and lead to cavitation over a long period of time .
the subsequent re - mineralization process is nearly the reverse . when oral ph returns to near neutral , ca and po4 ions in saliva incorporate themselves into the depleted mineral layers of enamel as new apatite .
the demineralized zones in the crystal lattice act as nucleation sites for new mineral deposition .
essentially , the sudden drop in ph following meals produces an under saturation of those essential ions ( ca and po4 ) in the plaque fluid with respect to tooth mineral .
this promotes the dissolution of the enamel . at elevated ph , the ionic super - saturation of plaque shifts the equilibrium the other way , causing a mineral deposition in the tooth .
over the course of human life , enamel and dentin undergo unlimited cycles of de - mineralization and re - mineralization . for many years
however recent reviews have concluded that the decline in caries may be at an end or even in reversal , with levels increasing in some areas .
thus , there is a need for developing new biomaterials which can act as an adjunct to the existing fluorides or can individually act as an agent for arresting the carious lesion and their remineralization . in the present study , we have compared the remineralization potential of two different dentifrices , which are not normally the key active ingredients in the dentifrices largely used .
considering the importance of the surface layer in caries progression , the evaluation of changes in this region is relevant , thus smh measurement is a suitable technique for studying de - remineralization process .
micro hardness measurement is appropriate for a material having fine microstructure , non - homogenous or prone to cracking like enamel .
smh indentations provide a relatively simple , non - destructive and rapid method in demineralization and remineralization studies . rather than using the traditional ph - cycling method ,
a modified version was utilized in our study , in an attempt to simulate the real - life situation .
this included a 3 h demineralizing cycle twice a day , with one 2 h and one intervening overnight remineralizing cycle , respectively . and to replicate early morning , midday and before bed - time tooth brushing , toothpaste was applied thrice daily .
the remineralizing solutions used in the study were created to replicate supersaturation by apatite minerals found in saliva and were similar to those previously utilized by ten cate and duijsters .
even though all the specimens were sectioned from different teeth , the variations among them did not yield any major effect on the progression of demineralization .
this was confirmed by the p - value obtained for all the hardness measurements ( p > 0.05 ) before the in - vitro ph cycling commenced .
it was therefore reasonable to disregard such variations when analyzing the data after ph cycling .
after the treatment regime with the respective dentifrices , increase in mean microhardness was observed in both groups [ table 1 ] ; this is in accordance with various previous studies carried out for determining the remineralization potential of bag , cpp - acp , and when compared group a and group b showed statistically significant values after ph - cycling regimen [ table 2 ] .
bag is a ceramic material consisting of amorphous sodium - calcium - phosphosilicate which is highly reactive in water and as a fine particle size powder can physically occlude dentinal tubules . in the aqueous environment around the tooth ,
i.e. , saliva in the oral cavity , sodium ions from the bag particles rapidly exchange with hydrogen cations ( in the form of h3o ) and this brings about the release of calcium and phosphate ( po4 ) ions from the glass .
a localized , transient increase in ph occurs during the initial exposure of the material to water due to the release of sodium .
this increase in ph helps to precipitate the extra calcium and phosphate ions provided by the bag to form a calcium phosphate layer . as these reactions continue
, this layer crystallizes into hydroxycarbonate apatite ( hca ) . unlike other calcium phosphate technologies , the ions that bag release form hca-(a mineral that is chemically similar to natural tooth mineral ) directly , without the intermediate acp phase .
these particles also attach to the tooth surface and continue to release ions and re - mineralize the tooth surface after the initial application .
these particles have been shown , in in - vitro studies , to release ions and transform into hca for up to 2 weeks .
a study was carried out to determine the remineralizing effects of bag on bleached enamel .
it concluded that bag deposits were found on the enamel surface of all the specimens , suggesting that they may act as a reservoir of ions available for remineralization at sites of possible demineralization .
the present study also revealed that cpp - acp remineralized enamel lesion in human enamel in - vitro .
cpp - acp is calcium phosphate - based delivery systems containing high concentrations of calcium phosphate .
the roles of cpp - acp has been described as - localization of the acp on the tooth surface and buffer the free calcium and phosphate ion activity , thereby helping in maintaining the role of super saturation .
the cpp stabilizes the calcium and phosphate in a metastable solution facilitating high concentration of the ca and po4 which diffuses in the enamel lesion when cpp - acp comes in contact with the lesion .
however the lower hardness values for cpp - acp may be due to its amorphous nature ; which does not adhere to the enamel surface , unlike bag gets attached to tooth , hence not remineralizing the tooth surface for a longer period of time to enhance its hardness .
a study investigated the enamel remineralization potential of cpp - acp and bag , showed that , after scanning electron microscope analysis it was clearly seen that although both group samples had plugs that sealed the fissures formed by demineralization , bag plug appeared to be more compact and intimately attached to the enamel surface .
the deposits formed by cpp - acp were smaller and amorphous , while bag created larger , more angular deposit .
this may also explain the high values of hardness for bag as compared to cpp - acp in the current study ; as bag attaches more intimately and compactly to the tooth surface .
under the current in - vitro experimental conditions it can be concluded that both bag and cpp - acp are capable to remineralize early carious lesion and also that bag has a better remineralization potential than cpp - acp .
 aims : the aim of this study was to evaluate and compare the remineralization potential of bioactive - glass ( bag ) ( novamin/calcium - sodium - phosphosilicate ) and casein phosphopeptide - amorphous calcium phosphate ( cpp - acp ) containing dentifrice.materials and methods : a total of 30 sound human premolars were decoronated , coated with nail varnish except for a 4 mm  4 mm window on the buccal surface of crown and were randomly divided in two groups ( n = 15 ) . 
 group a  bag dentifrice and group b  cpp - acp dentifrice . 
 the baseline surface microhardness ( smh ) was measured for all the specimens using the vickers microhardness testing machine . 
 artificial enamel carious lesions were created by inserting the specimens in de - mineralizing solution for 96 h. smh of demineralized specimens was evaluated . 
 10 days of ph - cycling regimen was carried out . 
 smh of remineralized specimens was evaluated.statistical analysis : data was analyzed using anova and multiple comparisons within groups was done using bonferroni method ( post - hoc tests ) to detect significant differences at p < 
 0.05 levels.results:group a showed significantly higher values ( p < 0.05 ) when compared with the hardness values of group b.conclusions:within the limits ; the present study concluded that ; both bag and cpp - acp are effective in remineralizing early enamel caries . 
 application of bag more effectively remineralized the carious lesion when compared with cpp - acp . 
INTRODUCTION
MATERIALS AND METHODS
Baseline SMH (B-SMH) measuring
Preparation of demineralizing and remineralizing solutions
Preparation of artificial carious lesion
After 96 h of initial demineralization SMH (D-SMH) measuring
Toothpaste preparation
The pH-cycling model
After remineralization SMH (R-SMH) measuring
Statistical analysis
RESULTS
DISCUSSION
CONCLUSION