The Change Of Temporomandibular Joint Disc After Mandibular Advancement During Treatment With Insulin In Diabetes Rats

Objective: The functional mandibular advancement plays an irreplaceable role in treating AngleⅡmalocclusion .It aims at the patients of the growing prophase and fastigium of adolescence. This treatment makes use of the growing potentials and the effect of the jaw born growth produced by masseter muscle to change the position of the sub maxilla and enhance the function of lateral pterygoid muscle and superficial masseter muscle. The research on functional mandibular advancement shows the temporomandibular joint disc is remodeled adaptively. With the changes of modern human beings'work, life style and the habit of diet, the morbidity rate of diabetes is increasing, at the same time the onset age is younger than before. Most patients of type1are adolescent. More and more diabetes patients need to treat the malocclusion. However the rebuilt of collagen fibers and cells are affected because of the osteoporosis and arthrosis with diabetes. Currently the researches about the change of the temporomandibular joint disc after the functional mandibular advancement on diabetes patients are quite few. This experiment built the model of functional mandibular advancement on typeⅠdiabetes rats. We monitored the changes of the temporomandibular joint disc during the experiment and discussed the feasibility to use the functional mandibular advancement on diabetes patients to provide academic theory of basic experience for clinical practice.Method: We need healthy male SD rats (3 weeks old) whose weight range from 45 to 55 grams .The first phase is to construct the models of diabetes rats and find the best dose of STZ: 112 SD rats were chosen and randomly divided into 16 groups to inject different doze of Streptozotocin (STZ):40mg per kilogram, 55mg/kg,60mg/kg,65mg/kg,70mg/kg,75mg/kg,80mg/kg,85mg/kg,90mg/kg,95mg/kg,100mg/kg,105mg/kg,110mg/kg,115mg/kg,120mg/kg,130mg/kg. Each group was injected the STZ after 24 hours fasting. 72 hours later, blood was extracted from caudal vein and urine was sampled before blood glucose and urinary glucose were respectively tested. Those rats whose blood glucose were above 16.7mmol/L and urinary glucose is above 1000mg/dl were diagnosed as diabetes.10 days later; we analyzed the number of achievement ratio and death rate to get the best dose for building models.The second phase is experiment of functional mandibular advancement: 105 male SD rats (3 weeks old) whose weight range from 40 to 50 grams were chosen and randomly divided into three groups of 35 rats, group A, the normal group; group B, diabetes group and group C, Insulin treated group. Each group randomly divided into 5 sub groups, the advancement group for 0 days, 7 days, 14 days, 21 days, and 30 days. Streptozotocin (STZ) was injected in rats of group B and group C with the amount of 85mg per kilogram. Rats in group A were injected with the same amount of sodium citrate. 72 hours later, blood was extracted from caudal vein and urine was sample before blood glucose and urinary glucose were respectively tested. Those rats whose blood glucose were above 16.7mmol/L and urinary glucose were above 1000mg/dl were diagnosed as diabetes. Four days after the model of diabetes mellitus was built, rats in group C began to receive subcutaneous injection at their necks. The amount of injection was adjusted according to the rats'blood glucose and urinary glucose till the blood glucose was 8-10 mmol/L. Group A and group B were given the same amount of normal saline injection. 10 days later, each group was equipped for the functional mandibular advancement lasting 24 hours.The rats of each group were killed by abstracting blood from their heart under general anaesthesia after 0 days, 7days, 14 days, 21 days and 30 days 7 days'expansion. We uncovered the left and right TMJs and broke out them inextenso. Then they were washed by isotonic Na chloride. The left TMJ was fixed by 4% paraformaldehyde for 72 hours. Then the decalcification was being done with 7%EDTA on it. About 6 weeks, this sample's anhydration was done and we embedded it for cutting it. After colored the sample with HE, we observed it under light microscope. The right TMJ was fixed by 2.5% glutaraldehyde over 24 hours (conserving it under 4℃). Then the sample's surface was spurted with gold. We observed it under electron microscope.Result: 1 The diabetes sample of 3-week-old rats: all the rats injected the STZ 85-95mg/kg after 24-hour fasting. This will build the best model.2 Observing the histological section: The changes of Group A and C have no difference. For 1 week, their collagen fibers were unbent and compact; anterior and posterior collagen fibers go forward and backward clearly; middle collagen fibers'wavilness were small; the posterior part showed some puerile cartilage cells. For 2 weeks, the temporomandibular joint disc'fibrosis were more evident, the posterior cartilage cells were increased obviously, cartilage cells at anterior and middle parts increased as well. For 3 weeks, the cartilage cells were riper, but the posterior fibers were thicker than the anterior ones, the middle part was compact and the fibers were more evident. Group B showed pathologic changes and the cartilage cells were lesser.3 Scanning electron microscope specimen: During the course of functional mandibular advancement, all the groups were adaptively remodeled to different extent. The group A and C are similar and have no evident differences. For advancing mandibular for 7 and 14 days, the remodeling is notable. The moire fabric of posterior and anterior disc was constructed in a more typical way. The anterior ripple is of striation and become more slightness. The posterior one is wide. The middle is knitted and is elongated along the aspect of arrow which is close and the wave is small. The fibriform film on the face is manifold. Group B showed more breach and gap of the ripple structure. The anterior and middle changes are less evident than the others. For advancing mandibular for 21 and 30 days, the fibriform film on the face is manifold. The groups A and C show no more evidence on adaptive remodeling. The group B showed more pathologic remodeling like breach and gap of the ripple structure.Conclusion: 1 Bones of Diabetes-modeled rats are soft, joint remodeling is restrained, after mandibular advancement, the joint is pathologically remodeled which is harm to mandibular advancement and sustainable improvement.2 Earlily good insulin controls contributes to the temporomandibular joint remodeling after treatment of functional mandibular advancement for Diabetes-modeled rats. There is no remarkable difference from the normal rats, and the effect of functional mandibular advancement is satisfactory.3 3-week-old Diabetes SD growing rats modeling and STZ doze : Intraabdominal Injection of 85-95mg/kg STZ after 24 hours fasting for the rats will make the modeling successful, and is the best doze .