An In Vitro Study Of Caries Risk After Orthodontic Interproximal Enamel Reduction

Objective: The aim of this study was to observe the caries risk of enamel after orthodontic interproximal enamel reduction(IER) by artificial dental caries with extracted teeth after interproximal enamel reduction, and applying evidence for clinical application of orthodontic interproximal enamel reduction.Methods:28 human premolars extracted for orthodontic reasons were collected for the experiment. Every premolar was split vertically into medial and distal haves. The samples were divided into 4 groups randomly,14 samples for each group. Group A was the control group, no treatment. In Group B, interproximal enamel reduction was made, but no polishing and remineralize treatment. In Group C, interproximal enamel reduction and polishing were made, but no remineralize treatment. In Group D, interproximal enamel reduction and polishing were made, then remineralize treatment was made with fluoride foam. Then caries was created in the four groups by pH cycling for 30 days in-vitro. The experiment was carried out at 37 centigrade. The enamel surface of morphology microstructure was examined using scanning electron microscopy(SEM) before and after the pH cycling. Before and after pH cycling, the microhardness of enamel surface of all samples was detected by microhardness testing machine. The date of each group was analyzed by SPSS13.0. The differences among mean values were compared by Student-Newman-Keuls multiple comparison test.Results:â‘ The decrease of microhardness in group B and C was larger than that in Group g after pH cycling (P<0.01), which means that caries risk of enamel in group B and C is bigger than that in group A. There were no statistical differences between group A and group D(P>0.05), which indicates that the caries risk of enamel in group A and group D is similar. The decrease of microhardness in group B and group C was no statistically significant different(P>0.05). The demineralization in group B and group C was same. The decrease of microhardness in group D was smaller than that in group B and group C (P<0.01), which means that, after interproximal enamel reduction, the caries risk of enamel with remineralization is lower than that without remineralization.â‘¡Before pH cycling, SEM images demonstrated that interproximal enamel reduction left a relatively rough enamel surface. The surfaces of enamels became smoother after polishing, but the scrapes can't be completely eliminated.After pH cycling, there was partial demineralization in samples of group A. The demineralization in group B and group C was serious. Demineralization happened on the whole surfaces after interproximal enamel reduction. There was steady matter deposited on the whole surfaces in group D.Conclusions:â‘ The caries risk of enamel after orthodontic interproximal enamel reduction increases if the surfaces are not treated with remineralizing.â‘¡If the surfaces are polished and treated with fluoride foam,the caries risk of enamel after orthodontic interproximal enamel reduction is the similar as that without enamel reduction.â‘¢Althougth polishing doesn't increase acidoresistance of enamel after orthodontic interproximal enamel reduction, it reduce the roughness of the enamel surfaces. Polishing is in favor of the precaution of the caries in clinical.