Interference Of Estrogen And Progesterone Induced Mandibular Condylar Resorption In Rats: An Experimental Study

Objectives The temporomandibular joint (TMJ) is the only linked-joint which hascomplex anatomical structure and physiological functions. Condyle is a compoent ofthe temporomandibular joint and condylar lesions directly affect the function of joints.Temporomandibular joint condylar idiopathic resorption (ICR) is a poorly understoodprogressive disease that results in an open bite, mandibular retraction which cause facialdisfigurement. Previous investigations found that adolescent women with lowerestrogen level or oral contraceptive history tend to ICR. However, so far no one hasreasonably explained why the ICR patients do not present systemic bone diseases likeosteoporosis but specific resorption only in condyle. We infer that the reason why ICRoccurs in condyle without bone loss in other parts of the body may have potentialassociation with the existence of estrogen receptor in condylar process. In this study,the estrogen and progesterone level was interfered in rats, trying to establish the animalmodel of ICR.Method Thirty female SD rats aged six weeks were divided into3groups: lavagecontraceptive drug group, cyclophosphamide induced premature ovarian failure groupand control group. The serum levels of estradiol were respectively determined beforeexperiment, on the15th day and at the end of12th week. All animals were put to deathand femoral bone mineral density was detected with bone density meter, histologicalobservation of the condylar process was performed by using light microscopy in thisexperiment. Result1.On the15th day and at the end of12th week, the serum levels of estradiol wereobviously decreased in the premature ovarian model group, and the difference wasstatistically significant (P＜0.05);On the15th day,no obvious change of estradiol levelwas found in the lavage contraceptive drug group（P＞0.05）,but the serum levels ofestradiol were obviously decreased on the12th week, and the difference wasstatistically significant (P＜0.05);2.No significant difference of rat femoral BMD wasfound between the groups （P＞0.05）.3.In lavage contraceptive drug group，thicknessof condylar cartilage decreased, trabeculae clutter and medullary cavity increased. In thepremature ovarian failure group, thickness of condylar cartilage was disorderlyarranged, trabeculae clutter and medullary cavity increased clearly.Conclusion1. Premature ovarian senility and long-term use short-acting contraceptivesmay result in the decrease of estrogen.2. Short-acting contraceptives and prematureovarian senility does not seem to cause femoral BMD decrease in anotherweight-bearing joint of young female rats.3. Contraceptive drug may destroyosteogenesis of condyle, after that condylar absorption occurred,premature ovarianfailure may result in osteoarthrosis of condyle and disorder of estrogen may induce ICR.