AN ATOMIC FORCE MICROSCOPE EVALUATION OF DENTAL EANAMEL SURFACE STRUCTURE FOLLOWING BEYOND COLD-LIGHT BLEACHING AND CPP-ACP TREATMENT

The study aimed to evaluate the dental enamel surface morphology following cold- light bleaching with/ without casein phosp-hopeptide-amorphous calcium phosphate (CPP-ACP) treatment. It provided important reference for that CPP-ACP’s capability promoting a slight remineralization of enamel. Methods: 30 clinical patients were randomly divided into three groups, with ten people in each group. Control group: cold-light bleaching, CPP-ACP group: cold-light bleaching and CPP-ACP paster, NaF group: cold-light bleaching and NaF. Negative control group is pre-operation. The silicone rubber mold of the leading front teeth were made quickly before and after treatment. Then epoxy resin moulding was performed and the moulds were put in 37℃ incubator for 24 hours. The morphology of enamel surfaces were observed with AFM. Results: The enamel surface was smooth and a small pit-like lacunae porous can be observed with AFM before treatment. Control group: Enamel column and interstitial can not be observed with AFM after cold-light bleaching, the enamel surface structure became rough and porous surface was uneven. CPP-ACP group: The roughness of Enamel surface was reduced, Micro fiber and coarse fiber bundle merged and pores were reduced. NaF group: Granular structure of enamel surface became smooth, the roughness was slightly bigger than CPP-ACP group, but few pores were observed, micro fiber and coarse fiber bundles were found in parallel with each other. Among treatment specimens of control group and CPP-ACP group, control group and NaF group, preoperative group and postoperative control group, a statistically significant differences (p<0.05) were identified. CPP-ACP group and NaF group have no significant difference (p>0.05). Conclusion: Cold light bleaching will cause enamel microstructure to change and the surface roughness to be increased. Postoperative application of CPPACP and sodium fluoride will both promote enamel mineralization, yet the former one is superior to the latter one, improving cold light bleaching effect.