| Objectives Dental enamel demineralization and staining around brackets are common problems in orthodontic clinical work.At present,penetrating resin therapy is the most commonly used treatment for the decrease of microhardness caused by enamel demineralization.However,penetrating resin therapy alone has limited ability to change the enamel color of demineralized and colored teeth.In this study,we compared the effects of artificial saliva self-remineralization,penetrating resin therapy,Opalescence Boost whitening system in consulting room combined with penetrating resin therapy in vitro at immediately,2 weeks and 4 weeks,to explore the best repair methods,and provide experimental basis for clinical application.Methods 1)Collection and Preservation of Samples: collect 120 extracted bicuspid teeth that due to orthodontic needs(first premolar and second premolar),Remove dental calculus,tissue debris,etc.,cover the teeth except the cheek surface with transparent anti acid nail polish and put them in artificial saliva.2)Sample preparation:(1)Establish orthodontic model: 120 teeth that in vitro were numbered,and brackets were bonded to the clinical crown center of the teeth,and placed in artificial saliva for reserve.(2)Prepare the model of demineralization and coloration of teeth in vitro: demineralization and coloration of teeth with cola to make the model of enamel demineralization and coloration after orthodontics.3)Grouping experimental treatment: 120 teeth in vitro were randomly divided into 4 groups,30 teeth in each group.Group A was a blank control group,without demineralization and coloration treatment,immersed in constant temperature artificial saliva and replaced regularly;Group B was an autonomous remineralization group,which was remineralized in constant temperature artificial saliva after experimental treatment;Group C was an penetrating resin treatment group;Group D was an Opalescence Boost whitening system in consulting room combined with penetrating resin group.Then,each group was randomly divided into three groups according to the test time,namely,10 teeth in each group were randomly tested at immediately,2 weeks and 4 weeks after the treatment.4)The surface morphology and color changes of the samples were observed with naked eyes;Vickers hardness tester was used to measure the microhardness of the enamel surface;Olympus Crystaleye spectrophotometer was used to do the colorimetric comparison of the enamel surface;and scanning electron microscopy was used to observe the micromorphology of the tooth surface.5)Statistical analysis: SPSS23.0 was used for statistical data analysis.The data of four groups were analyzed at different time after treatment.Statistical description use sx ±.The hardness data was analyzed by repeated measurement ANOVA.The value of chromatism was analzed by one-way ANOVA.The LSD method was used to make further comparison between two groups.The test standard was ?=0.05.The difference was statistically significant with P < 0.05.Results 1 naked eye observation: the enamel of normal teeth before demineralization and coloration treatment is smooth and glossy,translucent and opalescent,and there is no visible color difference on the surface of teeth;after demineralization and coloration treatment,the enamel surface of the non-bonded bracket part of the crown is brown,and the bonding part of the bracket floor is opalescent,which shows color difference obviously.After treatment with penetrating resin,the colour of the colouring part becomes lighter and the colour difference decreases obviously,but the colour differenceis still visible to the naked eye.After treatment of Opalescence Boost whitening system in consulting room combined with penetrating resin,there was no visible color difference on the surface of teeth,and the surface of enamel was glossy,which was basically consistent with the appearance of normal enamel.2.The results of surface microhardness test showed that the hardness of demineralized enamel in groups B,C and D was significantly increase than in different times with P<0.05.The hardness of demineralized enamel in different groups have statistic significance with P<0.05.The penetrating resin can restore the hardness of demineralized enamel immediately.3 Colorimetric results:The color difference of group A,B and C at different times have statistic significance with P<0.05,but the difference was not visible to naked eyes in group A,there was no significant difference in group D with P>0.05,and there was no visible color difference for naked eyes.Comparisons of color differences in different groups of teeth: By multiple statistical comparisons,group B and group C were compared with group A with P<0.05,the difference has statistically significant,group D with P>0.05,the difference has no statistically significant,which achieve aesthetic effect.4 Scanning Electron Microscope:Group of demineralization:the original normal enamel structure was destroyed,the surface was rough,a large number of honeycomb-like changes appeared,showing a lot of irregular pit-like acid etching appearance;Group of autonomous remineralization : The surface structure of the sample enamel changed obviously.The appearance of honeycomb and pit-like etched samples still existed,and did not completely restore to the normal enamel structure.However,the pit became shallow and the enamel was remineralized,which resulted in partial restoration of the surface structure;Group of penetrating resin: After penetrating resin treatment,the enamel surface did not show honeycomb pit-like etching appearance,the teeth surface was flat,and the enamel gap after demineralization was filled by penetrating resin;Opalescence Boost whitening system in consulting room combined with penetrating resin: No honeycomb pit-like etching appearance was observed on the surface of the enamel that treated by the experiment,and a small amount of minerals deposited on the surface,and remineralization occurs.Conclusions 1)Compared with other methods,penetrating resin can improve the surface microhardness of demineralized enamel instantly and effectively,and can meet the requirements of normal enamel hardness.2)Opalescence Boost whitening system can eliminate the color difference between the bracket bonding area and the coloring area around the bracket,and restore the normal color appearance of enamel.3)Opalescence Boost whitening system combined with penetrating resin treatment can meet the requirements of immediate restoration of microhardness and appearance of teeth.Figure 20;Table 2;Reference 101... |
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