| Objective:(1)study the effects of varnish XT and duraphat on enamel color change during fixed and invisible orthodontic treatment in vitro experiments.(2)study the effect of varnish XT and duraphat on the surface micro-hardhess of enamel during orthodontics in vitro in situ experiments.Methods: 1.According to the inclusion and exclusion criteria,120 premolars who needed to be extracted due to orthodontic treatment in July 2020 and were aged between 12 and 15 years old were collected.Cut off half of the root and extract the pulp.Number all the isolated teeth from 1 to 120,refer to the random number table and divide them into 6 groups,each with 20 isolated teeth.The groupings are as follows: group A: isolated teeth + resin attachment;group B: isolated teeth + resin attachment + Varnish XT;group C: isolated teeth + resin attachment +duraphat;group D: isolated teeth + metal brackets;Group E: isolated teeth + metal brackets + Varnish XT;group F: isolated teeth + metal brackets + duraphat.Soak in coffee at 37°C for 5 minutes × 4 times a day,and soak in artificial saliva for the remaining time.The L* a* b* color system recommended by the International Commission of Illumination was used for color analysis.Before the experiment,the baseline color of the 6 groups of isolated teeth was measured.On day 7 and 28,each group took out 10 isolated teeth and removed the brackets and resin attachment,after polishing the tooth surface,the enamel surface color L*,a*,b* is measured,and the calculation results are △L*,△a*,△b*,△E*.2.Collect 50 third molars extracted in the dentistry in July 2020 from who are between 18 and 25 years old,and cut the buccal enamel block of the crown to make enamel specimens.Number all enamel specimens from 1 to 50,refer to the random number table and divide them into 3 groups,each with 16 pieces.The groupings are as follows: Group A: enamel specimens + metal bracket;Group B: enamel specimens+ metal bracket + Varnish XT;Group C: enamel specimens + metal bracket +duraphat.At the same time,12 volunteers were recruited.According to the principle of random allocation,4 volunteers each were entered into Group A,B and C to make personalized enamel specimen molds.The enamel specimens mold was put into the volunteer’s mouth for 2 hours to form an acquired film on the surface of the tooth enamel.The volunteers gargled a cola drink for 5 minutes and repeated 4 times a day.Three hardness indentations were made on the edge of the bracket on the beginning of experiment,7th day,and 14 th day using a Webster microhardness tester with a load of50 g and a residence time of 15 s to determine the surface microhardness SMH of the enamel specimen.And take pictures under the scanning electron microscope on the beginning of experiment and day 14.Results: 1.The initial color L*,a*,and b* values of all teeth were analyzed by variance analysis,and the difference was not statistically significant(p>0.05).The teeth can be used in the experiment.(1)At day 7,the groups A and D had clinically identifiable color changes(△E*>3.7);through pairwise comparison,the difference between group A and group B,group A and group C,group D and group E,group D and group F was statistically significant.There was no significant difference between group B and group C,group E and group F,group A and group D,group B and group E,group C and group F.(2)At day 28,except for group B,the △ E* of the other groups was greater than3.7,and clinically unacceptable and identifiable color changes occurred;the results of the pairwise comparison(LSD-t test)can be seen: There are statistically significant differences between group A and group B,group A and group C,group B and group C,group D and group E,group D and group F,group E and group F.There is no statistically significant difference between group A and group D,group B and group E,group C and group F.(3)The △ E* of day 7 and 28 in each experimental group were analyzed by group t-test,and the differences in groups A,C,D,E,and F were statistically significant.(4)At day 7,the △L* showed a decreasing trend.The value of group D changed the most.There were statistically significant differences between group A and group B,group A and group C,group D and group E,group D and group F.At day 28,△L showed a decreasing trend in the whole day,the value of group D changed the most,the difference betweengroup A and group B,group A and group C,group B and group C,group D and group E,group D and group F,group E and group F was statistically significant.(5)At day 7,△ a* showed an overall increasing trend.The value of group D changed the most.There were statistically significant differences between group A and group B,group A and group C,group D and group E,group D and group F.At day 28,△a* showed an increasing trend in the whole day,and the value of group F changed the most.There were statistically significant differences between group A and group B,group B and group C,group D and group E,group E and group F.(6)At day 7,△b* showed an overall increasing trend.The value of group D changed the most,there were statistically significant differences between group A and group B,group A and group C,group B and group C,group D and group E,group D and group F,group E and group F.At day 28,△b* showed an overall increasing trend.The value of group D changed the most,there were statistically significant differences between group A and group B,group A and group C,group B and group C,group D and E,group D and group F,group E and group F.2.The initial surface microhardness SMH values of all enamel specimens were analyzed by variance analysis,and the difference was not statistically significant(p>0.05).The teeth can be used for the experiment.(1)The results of single factor analysis of variance of SMH% among the three groups at day 7 were statistically significant.Among them,the results of the pairwise comparison(LSD-t test)can be seen: Group A is higher than Group B and Group C,the differences between Group A and B,A and C are statistically significant,and there is no significance statistical difference between Group B and C.(2)The results of single factor analysis of variance of SMH% among the three groups at day 14 were statistically significant.The results of the pairwise comparison(LSD-t test)can be seen: group A is higher than group B and group C,the difference between group A and group B,group A and group C is statistically significant,group B and group C have no difference statistical significance.(3)The loss rate of enamel surface microhardness before and after 7 days and 14 days was tested by group t test.The difference of SMH% between 7 and 14 days in the first group was statistically significant.Other two groups was not statistically significant.Conclusion: 1.Clinically identifiable tooth surface color changes occurred in both the metal bracket and resin attachment orthodontic systems,and there was no statistically significant difference in color changes between the two.2.Both varnish XT and duraphat can reduce the change of tooth surface color during the process of orthodontic treatment.The effect is equivalent in the short term.Varnish XT is better than duraphat over time.3.Both varnish XT and duraphat can reduce the decrease of the surface microhardness of the enamel specimen.4.Varnish XT and duraphat have similar anti-demineralization effects in a short period of time.In the process of time,varnish XT shows more obvious advantages. |
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