The Study Of The Enamel And The Dentin Color Relapse To The Teeth Color Relapse After Bleaching A Short Time

ObjectiveIn addition to the uncertainty of tooth bleaching with immediate effect, theteeth color regression after bleaching a short period of time is another problemperplexing in dentists and patients. It’s a common concern that how much colorgradation of the teeth color can be improved after bleaching and to what extentteeth color regression after bleaching a short time. Current studies indicatesthat the reason of the teeth color regression is the change of the enamel oftranslucence, the dissolved demineralization of teeth enamel after bleachingre-building in oral environment. As the translucency of the recovering carries on,the below dentin color exposes more and more. The enamel and dentin is theprimary component of tooth hard tissue. Do enamel and dentin color regressionhave influence on teeth color regression?The aim of this study is to observe the influence of the color relapse for theenamel and the dentin on the teeth color change after bleaching a short time.MethodsTwelve freshly extracted non-carious human premolars for the orthodonticreason, free from enamel defect, were selected for this study. Discolored teeth,such as tetracycline teeth or teeth with fluorosis were excluded. With high speed dental drill along tooth length axis under water cooled，half of the dentalcrowns were removed. The specimens were serially ground flat by cloth anddiamond polishing paste and then enclosed it with resin. The specimens werefirstly bleached by15%carbamide peroxide for8h per day, with covering theenamel surfaces with1mm thickness of bleaching gel. Then the bleaching gelwas removed under running distilled water, and the specimens wereindividually kept in artificial saliva for the remaining16h. This procedure wasrepeated for14days.3weeks later, the color of the dental cusp, the middle andneck of the tooth on the lip surface near the middle-line, the enamel, dentin inthe dental cusp, and the middle and neck of the tooth on the section should bemeasured by the spectrophotometer, and the changes of the△E valuesshouldbe analyzed. The color measurements were performed in the following testingintervals, not only before bleaching but3weeks after withdrawal of bleaching.SPSS17.0statistical software was used to analyze data in this progress.ResultsAfter being bleached3weeks we found, on the surface view, the color ofthe teeth have relapse. The color regression at the incisal, cervical and thebody part of enamel ΔE respectively was2.38、2.28、2.06. The pairwisecomparison of the three did not have significant difference (P＞0.05).in various degrees, the enamel and the dentin regressed. The colorregression of body dentin was5.01, the color regression of cervical dentin was5.19, there are no significant difference between them. The color regression ofenamel was3.5; which has significant difference with dentin color’s (P＜0.05).The incisal surface of enamel was not significantly different from therelated profile surface (P＞0.05), but to dentin, the result was different (P＜0.05). ConclusionsA short time after bleaching, the enamel and the dentin color was relapse,the teeth color was significantly correlated with the changes of the enamel anddentin color.