| Objective:The purpose of this study was to investigate the interaction between the Beyond whitening method and the orthodontic bracket bonding.Method:Experiment One:The 50 premolars were randomly divided into 5 groups of 10 teeth.Group A was not subjected to any pretreatment and evaluated as a control group,was prepared for bonding brackets directly.The teeth in the other groups were bleached by the Beyond whitening system and then stored in artificial saliva.Following bleaching,Group B was prepared for bonding brackets immediately; Group C was stored in artificial saliva for 7 days;Group D was stored in artificial saliva for 14 days;Group E stored in artificial saliva for 28 days.The bond strength were tested by the tester.Any adhesive remaining after bracket removal was assessed with adhesive remnant index and scored with respect to the amount of resin adhering to the enamel surface.Observe the change of the enamel surfaces of each group by using SEM.Experiment Two:The 20 premolars were randomly selected,and the mesial part of buccal surface was experimental group and the distal part of buccal surface was control group.The experimental group was bonded with the bracket of the lower incisor. Before bonding each tooth was taken photo.After debonding the bracket the buccal surface was bleaching by the Beyond Whitening system,and then took photo again.Finally,the photo was input the computer,using the CIE analysis system to analyze the bleaching effect.Results:(1)The Beyond Whitening method affects the orthodontic bracket bonding.Compare to Group A,the P value of Group B,C,D,E was＜0.005,0.784,0.564,0.082,respectively.Group B showing the lowest mean value,differed significantly from Group A.(2)In the scanning electron microscope,the enamel surface on Group A was homogeneous,dense,flat and showed straight striations and widespread minute granules,but enamel structure was not observed.On group B, there was generally irregular exfoliation and bumpy on the enamel surface which was free of plaque and debris.Prism core and sheath failed to identify.On group C,apart from enamel was preferentially eroded in prism cores as rough efflorescent rock and an apparent increase in surface disperse porosity,surface mineral content precipitate was observed in this study.(3)After debonding the bracket, compare to Group A,the ARI scores showed the P value of Group B,C,D,Ewas＜0.005,0.421,0.421,0.065,respectively.Group B showing the lowest mean value,differed significantly from Group A.(4)The Beyond Whitening method can change the color of the tooth surface. Compare the Group A with Group B,the P value of the bleaching effect was 0.006.The△E value showed that the orthodontic bracket bonding can influence the effect of Beyond bleaching.Conclusion:(1)The Beyond Whitening method altered the enamel surface structure and made it demineralized,occur porosity and corrosion.Post-bleaching tooth was bonded orthodontic bracket immediately result in the shear bond strength reduced,and it makes that the shear bond strength can not reach the clinical need.(2)The expose of bleaching-treated enamel to artificial saliva for a prolonged period eliminates the reduction in bond strength that attends the immediate application of resin to bleached enamel.The experiment showed that storage of hydrogen peroxide bleached specimens in artificial salive for 7 days appeared to restore bond strength of brackets to a point and meet requirement of orthodontic clinical operation attributed to diffusion of residual hydrogen peroxide out of enamel and subsequent remineralization of the enamel surface structure lesions.(3)The digital photo-taken and computer CIE analysis system can anylyze the change of the color of tooth surface with quantitation.The Beyond Whitening system can make the color of the tooth surface have a visual change. The orthodontic bracket bonding reduces the effect of the Beyond Whitening.Therefore,after debonding the bracket it cannot operate the Beyond Whitening immediately.
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