| Objective:To establish the dental fluorosis model of SD rats under fluoride intake.To observe the effect of fluoride on tooth development in rats.The microstructure changes of different enamels were observed by scanning electron microscope,and the effects of fluoride on the appearance and microstructure of enamel were investigated.It provides a reference for the related clinical research of fluoride.Through the study of dental fluorosis whitening cases,the curative effect of whitening treatment and tooth sensitivity were evaluated and analyzed.Methods:①Thirty male SD rats(6 weeks)were randomly divided into 3 groups with 10 rats in each group.The control group was fed with deionized water without fluoride,the low fluoride group was fed with 50mg/L NaF deionized water,and the high fluoride group was fed with 100mg/L NaF deionized water to establish the dental fluorosis model.②The occurrence of dental fluorosis was recorded during the experiment.On day 0,A mark a was engraved on the distal gingival of the right mandibular incisor with a high-speed dental handpiece.After that,the gingival position of the right mandibular incisor was marked as b,c,d,e,f and g every week.The weekly eruption length m1,m2,m3,m4,m5 and m6 were measured with a vernier caliper.After feeding for 6 weeks,the mandibular incisors of rats were collected,and the total tooth length n was measured,and the values of ml/n and m6/n were calculated.③The tooth samples were observed and recorded.The enamel structure was observed by scanning electron microscope and the thickness of the enamel layer was measured and analyzed.④45 cases with dental fluorosis need whitening treatment in our oral cosmetic department were selected and classified according to the severity of dental fluorosis.The whitening curative effect of patients with different degrees of dental fluorosis and the sensitivity of whitening treatment were statistically analyzed and compared.Results:①There was no statistical significance between ml,m6 and n values among the blank group,low fluoride group and high fluoride group(P>0.05).The ml/n values of blank group,low fluoride group and high fluoride group were 0.21±0.03,0.19±0.02 and 0.21±0.05,there was no significant difference between the three groups(P>0.05).The m6/n values were 0.20±0.01,0.19±0.02 and 0.20±0.02,there was no significant difference between the three groups(P>0.05).②Normal enamel was uniform and translucent brownish yellow,while Enamel of dental fluorosis showed yellow and white stripes and chalky spots.③After 6 weeks,the enamel surface of 20 teeth in blank group was normal;In the low fluoride group,2 had normal enamel,14 had striate changes,and 4 had chalky spots changes.In the high fluoride group,there were 0 normal enamel,8 striate enamel and 12 chalky spots enamel.④Under electron microscope,the enamel column of normal enamel was uniform and strong,with clear arrangement rules and braided shape.The enamel column of dental fluorosis was smaller,the arrangement direction changed,and the normal braided structure was lost.The striped enamel column was arranged in a regular unidirectional manner,while the chalky spots enamel column was arranged in an irregular and disordered unidirectional manner.⑤By measurement of enamel thickness,normal enamel>stripe enamel>chalky spots enamel.⑥The curative effect of moderate and severe dental fluorosis was worse than that of mildly dental fluorosis(P<0.05),and the sensitivity rate was also higher(P<0.05).Conclusion:①The replacement period of mandibular incisors in rats was 5 weeks,and fluoride did not affect the replacement period.②Fluoride can cause streaky and chalky spots changes in rat enamel,the low fluoride group mainly showed streaky changes,and the high fluoride group mainly showed chalky spots changes.③Fluoride can change the arrangement of enamel column and decrease the thickness of enamel layer.④The enamel structure of mildly dental fluorosis is complete,and whitening treatment has good effect and low sensitivity.The enamel thickness of moderate and severe dental fluorosis is reduced,the structure is disorganized,the effect is poor and the sensitivity is high. |
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