Effect of topical fluoride application on eroded enamel in vitro

AIM:To evaluate the effect of different topical fluoride application on the eroded enamel in vitro.METHODS: Forty freshly extracted human premolars for orthodontic purpose without caries and cracks were selected.Two enamel samples were prepared from each crown.All samples were randomly divided into four groups: control,0.1% NaF solution,fluoride toothpaste and strengthened group.The samples were discontinuously immersed into soft drink for one week,then treated with different fluoride for another week.The surface micro-hardness(SMH) was measured and the surface morphology was observed under Scanning Electrical Microscope(SEM) and Atomic Force Microscope(AFM).RESULTS: The SMH of enamel after erosion was significantly lower than the SMH before erosion in each group,but there was no difference between groups.The increase of SMH of group treated with fluoride was statistically higher than that of control(P0.001).The AFM and SEM examination indicated a honey-comb structure after erosion and SEM showed the deposition on the enamel surface after fluoridation.CONCLUSION: The enamel surface can be demineralized by soft drinks and the eroded enamel can be remineralized by fluoride in vitro.