Study Of The Effect Of Nd:YAG Laser Irradiation On Enamel Demineralization

The purpose of this study was to investigate the effect of Nd:YAG laser irradiation on enamel demineralization after orthodontic treatment with fixed appliance, through the investigation of incidence of enamel demineralization and the test of comparing the ability of reducing demineralization on enamel between Nd:YAG laser and fluoride.This study included five parts, part I. Studying the incidence of enamel demineralization and the most susceptible teeth and area of enamel demineralization after orthodontic treatment with fixed appliance .Part II , determining the optimal energy of Nd:YAG laser irradiation on enamel through observing the morphologic changes of the enamel surfaces exposed to Nd:YAG laser with a SEM. Part III, among 80 orthodontic patients, one side upper lateral incisor was irradiated with Nd:YAG laser at a energy 40mj 15pps and the other side upper lateral incisor was coated with 2% sodium fluoride on the surface of enamel, then evaluating the effect on reducing demineralization between them. Part IV, 12 healthy premolars, which were randomly divided into two equal groups, one was coated by 2% sodium fluoride and the other was irradiated by Nd:YAG laser at a energy 40mj 15pps , being put in artificial oral system for 7 days, were observed the attachment of the bacteria to the surface of enamel with SEM and compared their difference .Part V, Observing the histological and morphological alteration of enamel ,which were treated by Nd:YAG laser at aenergy 40mj 15pps or 2% sodium fluoride and have been put in artificial oral system for 7 days, with SEM and PLM and then comparing their difference.1. The result of studying the incidence of enamel demineralization suggested that the incidence of demineralization in the orthodontic treated group is obviously higher than the control group .and the patients, whose oral sanitation surroundings are bad, more easily suffer enamel demineralization than other patients. The most susceptible teeth to demineralization were maxillary incisor and the most susceptible area is dental cervix.2. The result of observing the morphologic changes of the enamel surface exposed the different energy Nd:YAG laser suggest the 40mJ 15pps is the optimal irradiation intensity to enamel. At such energy density, the micropores and focal holes on the enamel are melted and sealed. There is not obviously visual damage to the enamel.3. The result of comparing the effect on reducing enamel demineralization between Nd:YAG laser and fluoride shows that both Nd:YAG laser and fluoride can reduce the demineralization of enamel, especially, the NdrYAG laser is more effective than fluoride to those patients whose oral sanitation environment is bad.4. The result of observing the effect on attachment of the bacteria to the surface of enamel shows that fluoride can postpone the mature of streptococcus, the Nd:YAG laser can affect the adherence of bacillus to surface of enamel and make the tridimensional structure of plaque loose.5. Analyzing the morphological alternation of enamel with PLM and SEM, we can see that fluoride can promote the remineralization of enamel ,and there are a lot of remineralizational crystal sediment on the teeth surface, moreover theNd:YAG laser can inhibit the demoralization under the surface zone of enamel .we can observe a obvious surface zone and the thinnest body of the lesion among the three group.From these study , we can conclud that the Nd:YAG laser can reduce demineralization of enamel by sealing the micropores of the enamel surface, and affecting the structure of plaque ,the fluoride can promote enamel remineralization as well as FAP formation to prevent enamel from forming white spot and caries in orthodontic. As a orthodontist, we should choose corresponding means on the basis of the patient's concnete oral circumstance to prevent from the appearance of ennmel demineralization in the procession of our treament.