An In Vitro Study Of Remineralization Potential Of CPP-ACP After Interproximal Enamel Reduction

Objective To evaluate the preventive effect of casein phosphopeptide-orphous calcium phosphate (CPP-ACP) on enamel demineralization after interproximal enamel reduction (IER) in vitro, and to assess validity of the method of using Computer-assisted image analysis of circularly polarized images to quantify enamel demineralization.Methods40human premolars extracted for orthodontic reasons were collected for the experiment. Mesial and distal surfaces were sectioned into80samples. The samples were assigned to4groups randomly. Group A was the control group, no treatment. In Group B, interproximal enamel reduction and polishing were made, but no remineralize treatment. In Group C, interproximal enamel reduction and polishing were made, then remineralize treatment was made with fluoride foam. Group D, similar to Group C, but remineralize treatment was made with CPP-ACP. Then caries was created in the four groups by pH cycling for60days in-vitro. The experiment was carried out at37℃. The polarize images of each tooth was taken by one operator, and the computer assisted image analysis system was used to record the mean grey level of the demineralized area. Micro hardness tester was used to record the micro hardness of demineralized area. The data was analyzed in SPSS17.0microware package. At the same time, the compare between the means of different groups was done by Multiple Factors Variance Analysis. The differences among the same group were measured by LSD-t test. The enamel surface of morphology micro structure was examined using scanning electron microscopy (SEM) after the pH cycling.Results①The mean grey level of group B is highest. The mean grey level of group C and D both decreased. The mean grey level of group A is lowest. The mean grey level of group B is higher significantly than that of the other groups (p=0.000).But there is no significant difference among group A、D and C (p=0.113,0.665), while it was statistically different (P=0.045) between group A and group D.②The micro hardness of group A is highest. The micro hardness of group B is lowest. The micro hardness of group C and D both increased. The micro hardness of group B is lower significantly than that of the other groups (p=0.000,0.003).There is no significant difference among group A、C and D (p=0.152,0.294). But there is significant different between group A and C (p=0.017)③There is partial demineralization in samples of group A. The demineralization in group B is serious. Demineralization happened on the whole surfaces after interproximal enamel reduction. There is steady matter deposited on the whole surfaces in group C and D.Conclusions①The demineralization of enamel after IER is serious if the surfaces were not treated with remineralizing,with decrease of the mean grey level and increase of the micro hardness.②If the surfaces were treated with fluoride foam or CPP-ACP after IER, the mean grey level of the enamel surface decreased, the micro hardness of the enamel surface increased. They both could improve the micrological condition and proceed the remineralization of the enamel.③Computer-assisted image analysis of circularly polarized images is an effective quantifying method of assessing enamel demineralization.