Modeling And Immunohistochemical Study On The Effectof Orthodontic Brackets On Oral Mucosa In Rats

Objective: To simulate the mechanical and chemical stimulation of brackets on the mucosa in rat oral cavity.To explore the stimulation of bracket to mucosa and tissue recovery after removal of bracket,and compare three different brackets,so as to provide experimental basis for clinicians and patients to choose orthodontic brackets.Methods: Forty-eight healthy male Sprague-Dawley(SD)rats aged 3 month were selected.After one week of adaptive feeding,rats were randomly divided into experimental group: domestic self-locking group(12 rats),imported self-locking group(12 rats)and domestic square silk group(12 rats).Control group: negative control group(12 rats).According to the experimental period,each group was divided into 14 days and 28 days.Domestic self-locking group,import self-locking group and domestic square silk group had 6 rats in each group,a total of 8 groups.In the experimental group,three brackets were sutured on the labial side of the lower anterior teeth of three groups with the same suture method(in natural condition,the lower lip can cover the bracket);in the negative control group,the same suture method was used,and the appliance and suture were worn 24 hours a day.At 14 days after suture,the mucosal status and body weight of all rats were recorded.The rats in 14 days group were sacrificed and the brackets and sutures were removed in 28 days group.At 28 days,the mucosal status and body weight of rats in 28 days group were recorded,and the samples were sacrificed.All animals were fed on soft food,drinking water freely and under the same environment until the end of the experiment.The mucosa of the lower lip was fixed,dehydrated and embedded routinely.After paraffin section,routine HE staining was used to observe the histological changes of mucosa.Immunohistochemical method was used to detect the expression of CD4 and CD8.Immunohistochemical staining score was made by cell image analysis system,and the intensity of staining was expressed by IHS value.Image-pro-plus image analysis system was used for semi-quantitative analysis.All data results were processed by SPSS19.0 statistical software.T test was used to compare the experimental group with the control group,and independent sample t test was used between different experimental groups and experimental groups.CD4 and CD8 were analyzed,and the test level was a=0.05.Result:1.Observing the mucosal state and HE staining with naked eyes,the three brackets showed different degrees of oral mucosal reactions at 14 days.The severity of mucosal reactions ranked from heavy to light as follows: homemade square wire > homemade self-locking > imported self-locking.2.Immunohistochemistry was used to measure CD4 IHS value and statistical analysis showed that there were significant differences between domestic self-locking for 14 days [91.5(15.5)],import self-locking for 14 days [54.0(7.5)],domestic square silk for 14 days [115.5(21.0)] and negative control for 14 days [42(25.5)](P<0.05).The degree of immune response of the three brackets was: homemade square wire>homemade self-locking> imported self-locking(P<0.05).There was no difference among the three brackets at 28 days(P>0.05).However,the immune response of mucosa was greater than that of negative control group(P<0.05).3.Immunohistochemistry was used to measure CD8 IHS value and statistical analysis showed that there were significant differences between domestic self-locking for 14 days [105(19.5)],import self-locking for 14 days [73.0(39.5)],domestic square silk for 14 days [130.5(19.5)] and negative control for 14 days [49(22.5)](P<0.05).The degree of immune response of the three brackets was: homemade square wire > homemade self-locking > imported self-locking(P<0.05).At 28 days,there was no difference between domestic self-locking group and negative control group(P>0.05).There were differences between the other two groups and the negative control group(P<0.05).Conclusion:1.The rat model of bracket stimulation to mucosa was successfully established.2.Different kinds of brackets have different damage to oral mucosa.Among the three kinds of brackets tested,square wire brackets have the most serious damage and imported self-locking brackets have the least damage.3.Brackets have certain mechanical damage and immune effects on mucosa.After removal of brackets,the repair of the damage tends to be normal gradually.