An In Vitro Study Of Enaml With Different Orthodontic Interproximal Enamel Reduction Methods

Expermient 1 Study on enaml with different orthodontic interproximal enamel reduction methodsObjective:The aim of this study was to observe, measure and compare the effect of remineralization with different interproximal enamel reduction (IER) methods by PH cycles in vitro. After that, the best was chosen, and put into practice in clinic.Methods:50 human premolars extracted for orthodontic reasons were collected for the experiment. After removal of the root, the crown was split vertically into two halves with wafer-thin wheel blade. Then the 100 samples were randomly divided into 5 groups,20 samples for each group. Every group was reduced enamel with different IER methods: groupâ… , stripping strip; groupâ…¡stripping disk; groupâ…¢,stripping strip with polishing system with 35% orthophosphoric acid; groupâ…£, stripping disk with polishing system with 35% orthophosphoric acid; groupâ…¤, control. All the samples were treated with PH cycles in vitro for 30 days. The microhardness of enamel surface of all samples was detected by microhardness testing machine. The enamel surface morphology of microstructure was examined by scanning electron microscopy(SEM). And also the effect of remineralization of each group was analyzed by SPSS13.0 Microsoft ANOVA test.Results:â‘ ANOVA detected statistically significant differences between groups (F=13.89,P=0.000). And from the mean microhardness, groupâ…¡was the lowwest and groupâ…¢was the highest. The post SNK-q test showed that there were no statistically significant differences between groupâ… and groupâ…¡, groupâ…¢and groupâ…£(P>0.05); Also there were statistically significant differences between groupâ… and groupâ…¢, groupâ… and groupâ…£, groupâ…¡and groupâ…¢, groupâ…¡and groupâ…£(P<0.01). And there were statistically differences between groupâ… and groupâ…¤, groupâ…¡and groupâ…¤, groupâ…¢and groupâ…¤, groupâ…£and groupâ…¤(P<0.05).â‘¡From naked eye and SEM, there were no obviously difference between the two chemical polishing groups, but they were better than the others.Conclusions:â‘ There is no significant difference between strip and disk by PH cycles.â‘¡Chemical polishing group is better than the others by PH cycles.â‘¢The furrows of the enamel surface caused by IER are hardly repaired even after remineralization.Expermient 2 Study on remineralization with different fluoride afer orthodontic interproximal enamel reductionObjective:The aim of this study was to observe, measure and compare the effect of remineralization with different fluoride agents by PH cycles in vitro. After that, the best was chosen, and put into practice in clinic.Methods:30 human premolars extracted for orthodontic reasons were collected for the experiment. After removal of the root, the crown was split vertically into two halves with wafer-thin wheel blade. Then the 60 samples were randomly divided into 2 groups,30 samples for each group. Every group was reduced enamel with different IER methods: group A, stripping strip with polishing system with 35% orthophosphoric acid; group B, stripping disk with polishing system with 35% orthophosphoric acid. Each of the group above was divided into 3 sub-groups based on the fluoride agents (fluor protector; fluoride foam and contorl),10 samples for each sub-group. All the samples were treated by PH cycles in vitro for 15 days. The microhardness of enamel surface of all samples was detected by microhardness testing machine. The enamel surface of morphology microstructure was examined by scanning electron microscopy(SEM). The effect of remineralization of each group was analyzed by using SPSS13.0 Microsoft ANOVA test.Results:â‘ Group A:ANOVA detected statistically significant differences between sub-groups (F=11.73, P=0.0015). And from the mean microhardness, fluor protector was the highest and the contorl was the lowwest. The post SNK-q test showed that there were no statistically significant differences between treatment with fluor protector and the treatment with fluoride foam(P>0.05), which meant the effect of remineralization in the two groups was the same after IER. Also there were statistically significant differences between treatment with fluor protector and the control (P<0.01), which meant the effect of remineralization in treatment group with fluor protector was better than the control group after IER. And there were statistically differences between treatment with fluoride foam and the control (P<0.05), which meant the effect of remineralization in treatment with fluoride foam was better than the control after IER.â‘¡Group B:ANOVA detected statistically significant differences between sub-groups (F=9.33, P=0.0036). And from the mean microhardness, fluor protector was the highest and the contorl was the lowwest. The post SNK-q test showed that there were no statistically significant differences between treatment with fluor protector and the treatment with fluoride foam(P>0.05), which meant the effect of remineralization in the two group was the same after IER. Also there were statistically significant differences between treatment with fluor protector and the control (P<0.01), which meant the effect of remineralization in treatment group with fluor protector was better than the control group after IER. And there were statistically differences between treatment with fluoride foam and the control (P<0.05), which meant the effect of remineralization in treatment with fluoride foam was better than the control after IER.â‘¢From naked eye and SEM, there were no obviously difference between the two fluoride agents, but they were better than the control.Conclusions:â‘ There is some effect of renineralization after PH cycles in vitro with different IER methods and fluoride agents.â‘¡Flour protector and fluoride foam have some effect of remineralization.â‘¢The furrows of the enamel surface caused by IER are hardly repaired even after remineralization.