| Objective: The aim of this study was to evaluate the effects of shear bond and the surface of enamel added fluoride in different times. The enamel demineralization and remineralization may keep a dynamic equilibrium in normal, enamel demineralization will not happen. But the enamel demineralization can happen in the first month after bonding brackets. Fluoride has the effectiveness to prevent demineralization and help remineralization during orthodontic treatment. During orthodontic treatment, using fluoride before etching, during etching or after etching can prevent enamel demineralization. But the shear bond strength and the surface of enamel will be effected or not are the problems which doctors care.Materials and method: To select 96 human premolars which extracted for orthodontic reasons. All of them were stored in a 0.5%chloramine T at 4℃. The brackets were edgewise resin made in China with a cross section 0.022×0.028 inches and with a base area 11.84 mm2. 96 premolars were divided into 4 groups of 24. Group A, group B, group C, group D. The surface of enamel was observed with electron microscope. Group A etched, group B covered with fluoride form for 4min before etching. 2% NaF were added into phosphoric acid of group C .Group D covered with fluoride form for 4min after etching. The enamel surface of these premolars were observed with microscope. All the brackets bonded routinely according to the directions of the manufacture .After ten minutes, the teeth specimens were stored in artificial saliva at 37℃for 24hours. Took the teeth out after they were dried. Then do thermocycling tests, using the hydroplus to test the shear bond strength. The surface of enamel with electron microscope should be observed right after the brackets have been removed. First research of this experiment: to see thesurface of enamel after different methods dealing with the enamel with fluoride. The second research of this experiment: to see the shear bond strength after different methods dealing with the enamel with fluoride. The third research of this experiment: to see the surface of enamel with electron microscope after removing the brackets. Compare the three methods to see the effects of shear bond strength and surface of enamel added fluoride to find the best methods which meet the requirement of orthodontic therapy.Results:1 Group A, group B and group C all have reagent in depression.2 The shear bond strength of group A is the strongest, the next is group D.3 Group D has the largest reagent in depression after the brackets have been removed.4 ARI score showed group B and group D had less adhesive remained after brackets removed. The enamel surface was examined in a megaloscope at 10 magnification, 5 enamel fracture happened in compared group. Enamel fracture were not happened in other groups. Most of the adhesive resin in group B and group D exhibited enamel/adhesive interface. Added fluoride before and after acid etching are good methods.Conclusions: All of the three methods with fluoride can satisfy clinical needs. Covered with fluoride foam before or after etching are good methods in clinic, and they had large reagent in depression, little adhesive remained after brackets removed. But how long should we give fluoride will be investigated.
|
PDF Full Text Request