| Objectives In the process of orthodontic treatment,some cases require quantitative grinding of the adjacent surface of the enamel,which is called interproximal enamel reduction(IER).However,the IER will cause some damage to the tooth body,and may cause allergic discomfort or enamel demineralization.In severe cases,it can cause dental caries.Therefore,surface of the enamel after IER needs to be properly treated to prevent or reduce the damage to the teeth.In this study,by simulating the saliva environment of the oral cavity and the vitro pH cycle,the newly extracted teeth were treated with penetrating resin,tooth protector,and fluorinated foam.It was observed that the clinical effects of three reagents on promoting enamel remineralization and inhibiting enamel demineralization after IER.Provide experimental basis for clinical selection of the best treatment reagent after IER.Methods 1 Collection and storage of samples: Collected 105 premolars(12 to 18 years old female,non-high-fluoride area teeth,non-tetracycline,no visible caries and defects,no cracks and horizontal lines,no chalky plaques caused by demineralization,no treatment of teeth and pulp)required for orthodontic treatment in the Department of Oral Surgery of the North China University of Stomatology Stomatological Hospital.remove tartar deposition,pigmentation and tissue debris on the tooth surface,then place cleaned isolated teeth in pHysiological saline,and store it in a refrigerator at 4 degrees Celsius.2 preparation of samples(Establish a model of interproximal enamel reduction): 105 extracted teeth were embedded in plaster,exposing only the complete crown.Use the deglazing bur to grind0.2mm enamel on the mesial and surfaces of the teeth,and polish with a polishing sand bar.The crowns were split in the mesial and distal directions along the check and tongue,and the roots were removed to obtain two samples.A total of 210 samples were obtained from105 extracted teeth.3 Group experiment processing: The IER surface of each sample only retains the 4mm×4mm window area,and the area outside the window area is closed with an antacid nail polish.Ten samples were randomly selected from the 210 samples as the control group.The X-ray energy spectrum analyzer was used to measure the calciumphosphorus ratio of five sample and the surface microstructure was observed with a scanning electron microscope.The remaining 200 samples were randomly divided into 8groups(A1,A2,B1,B2,C1,C2,D1,D2)of 25 samples each.After grouping,5 samples were randomly selected from each group to measure the microhardness of the enamel surface.The remaining 20 samples in each group were processed as follows.Groups A1 and A2: no treatment after IER;Groups B1 and B2: treatment with infiltration resin after IER;samples of this group were treated with penetrating resin only once in the experiment;Groups C1 and C2:samples were treated with tooth protector after IER.The samples of this group were applied to remove the glaze with the protective tooth every day and evening,and rinsed with deionized water after 5 minutes;Groups D1 and D2: After IER,use fluorinated foam to process.The sample was immersed in fluorinated foam for 5 minutes and then removed.After 30 minutes,rinse thoroughly with deionized water and use it once every 2 weeks for 5 times.This experiment lasted a total of 60 days,place the vessel containing the solution and sample throughout the 37℃ thermostatic water bath.The four groups of samples A1,B1,C1 and D1 were placed in artificial saliva,and the four groups of samples A2,B2,C2 and D2 were placed in artificial demineralizing fluid for 2 hour each day,and the remaining time was soaked in artificial saliva for in vitro PH cycle.The artificial demineralization fluid and artificial saliva were changed daily.The samples were thoroughly rinsed with deionized water before and after each fluid change or experimental treatment.4 Detection: The micro-hardness meter measures the surface micro-hardness value of the unglazed window area;the X-ray energy spectrum analyzer measures the deglazed mineral content and calculates the calcium-pHospHorus ratio;the scanning electron microscope observes and compares the un-glazed column and glaze MorpHology of the column gap.5 Statistical analysis: Use SPSS23.0 for statistical analysis of the experimental data of the samples,and statistical description of (?)±s was used.First,the homogeneity of variance of the surface microhardness value and the calcium-phosphorus ratio of the unglazed surface were tested separately.The values between groups were analyzed by single factor analysis of variance.The comparison of microhardness values was performed using the repeated measures analysis of variance;further pairwise comparisons between means were performed using the LSD test.Test standard α=0.05.Results 1 Test results of surface microhardness: The surface micro hardness values of the four groups A1,B1,C1 and D1 after the in vitro remineralization simulation experiment were all greater than the surface microhardness values before remineralization,and the differences were statistically significant(P<0.05).the difference in group A1 is small,and the difference in group B1 is the largest.There was no statistical difference between the surface microhardness valuses of each group before remineralization;the surface microhardness values of the grouops A2,B2,C2 and D2 after the end of the in vitro pH cycle simulation experiment were all smaller than those before the in vitro pH cycle Microhardness value,and the difference is statistically significant(P<0.05),where the difference in the A2 group is the largest,and the difference in the B1 group is the smallest.There is no statistical difference between the surface microhardness values of each group before the pH cycle.2 X-ray energy spectrum analysis results: the comparison between the calcium and pHospHorus ratios of the control group,A1,B1,C1,and D1 groups shows that C1> D1> A1> B1 > control group;A2,B2,C2,D2 five groups of calcium and pHospHorus ratio comparison results showed that B2 > C2 = control > D2 >A2.3 Scanning electron microscope observation: The scanning electron microscope of the control group shows that the rough surface covered with scratches and cracks can still be seen on the IER surface of the adjacent surface even after careful polishing;The IER surface of the A1 group is uneven,with obvious scratches,and sparsely arranged particles or flakes can be seen on the enamel surface;The IER surface treated with penetrating resin in group B1 is relatively smooth,and densely arranged penetrating resin can be seen in the gap between the glaze columns;Group C1 is treated with daily tooth protector,the surface is smooth,and more granular or lumpy deposits can be seen in the enamel column gap and enamel surface;The surface of group D1 is not smooth,the ends of the glaze columns are more complete,and more flaky or lumpy deposits can be seen in the gap between the glaze columns;Group A2 can be found under scanning electron microscope observation that the IER surface has a more serious demineralization phenomenon after extracorporeal pH cycling,the demineralized pores are large and there are a large number of demineralized pits,showing “ acid-like ”;The surface of group B2 is relatively smooth,with few obvious demineralized pores,and protrusion resins in the glaze column gap;The surface of group C2 is smooth,the ends of the glaze columns are incomplete,there are fewer demineralized pores,and a small amount of high-density flaky or granular deposits can be seen on the enamel surface;The IER surface of group D2 was not smooth,some demineralized pores were visible under the electron microscope,and a small amount of granular or lamellar mineral deposits were found.Conclusions 1 Experiments show that the remineralization effect of different agents on the enamel after IER of the adjacent teeth is different.Compared with the penetrating resin and fluorinated foam,tooth protector has the best effect of promoting demineralization of IER surface.2 Penetrating resin can effectively inhibit the demineralization of the IER surface,followed by the effect of dentin,and both reagents are superior to fluorinated foam.Figure31;Table4;Reference 109... |
PDF Full Text Request