| OBJECTIVES:To analysis the effect of bleaching to teeth enamel surface vicker's microhardness through measuring human teeth enamel surface vicker's microhardness before bleaching, immediately after bleaching and after treatment by each regent in vitro for 14 days, offer reference for clinical applicationMETHODS:Adopting micro-indentation hardness tester measured sixty specimens enamel surface microhardness before bleaching.The specimens were randomly divided into four groupsGroup A:Beyond bleaching gel and Beyond bleaching apparatus (n=15);Group B:Everbrite bleaching gel and BT cool LED bleaching apparatus (n=15);Group C:Beyond bleaching gel and BT cool LED bleaching apparatus (n=15);Group D:Everbrite bleaching gel and Beyond bleaching apparatus (n=15);All specimens besmeared bleaching gel respectively and irradiated for eight minutes by cold light for three times.Adopting micro-indentation hardness tester measured all specimens enamel surface microhardness immediately after bleaching.Each experimental group was subdivided into three groups according to the postbleaching treatment:storaged in human saliva (group A1, B1, C1,D1) (each group n=5) storaged in artificial saliva (group A2, B2, C2, D2) (each group n=5)storaged in distilled water (group A3, B3, C3, D3) (each group n=5)Measured all specimens enamel surface microhardness after 14 days treatment in vitro.All datas were analyed statistically,with the software SPSS 17.0, datas in group by matching t-test, datas between groups by one-way ANOVA or Kruskal-Wallis H test.RESULTS:1. All the specimens enamel surface microhardness before bleaching were 243.70 to 341.94 kg/mm2, there were no significant difference by analysis of variance (P> 0.1).2. Each group tooth enamel surface microhardness immediately after bleaching significantly reduced compared with before-bleaching, there was significant difference by t-test (P< 0.01). The impact of reduction of tooth enamel surface microhardness of group B was the maximum, group D was second, group A was third and group C was the minimum. The difference of teeth enamel surface microhardness between groups before and immediately after bleaching compared by one-way ANOVA, there was significant difference(P< 0.05),SNK-q inspection results:results group A and group C,group A and group D had no significant difference (P> 0.05), between group B andgroup D had no significant difference (P > 0.05),results group B and group A,group B and group C were significantly different (P< 0.05). It indicated that Beyond bleaching apparatus cooperated to Beyond or Everbrite bleaching gel had the same effect to the difference of enamel surface microhardness before and immediately after bleaching, while the impact of tooth enamel surface microhardness was less when BT cool bleaching instrument jointed Beyond bleaching gel. 3. Teeth enamel surface microhardness increased significantly after treated by human saliva for 14 days compared with the level immediately after bleaching, it could restore to the level before bleaching; Teeth enamel surface microhardness increased significantly after treated by artificial saliva for 14 days compared with the level immediately after bleaching,but it was difficult to restore to the level before bleaching; Teeth enamel surface microhardness decreased significantly after treated by distilled water for 14 days compared with the level immediately after bleaching.CONCLUTIONS:1. Human enamel surface microhardness significantly reduced immediately after Everbrite and Beyond cold light-bleaching.2. The increase of enamel surface microhardness after treated by human saliva was the most obvious, it indicated that human saliva was ideal remineralization fluid,artificial saliva also caould obviously increase enamel surface microhardness, distilled water didn't have the effect.3. Beyond bleaching apparatus had the same effect to two bleaching gels of this research, any kind of two bleaching gels of this reserch could cooperate to Beyond cold bleaching apparatus. |
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