Effect Of Altered Functional Loading On The Growth Of Condyle Cartilage And Subchondral Bone In Rabbits

ObjectiveAltered loading is an important etiological factor for temporomandibular joint (TMJ) disorders. The goal of this study was to develop a TMJ altered functional loading model in New Zealand white rabbits,and investigate the effect and change of altered functional loading on the condyle cartilage and subchondral bone.MethodsTwenty seven,2-month-old rabbits, weight 1.5 to 2.0 kg, were divided into three groups randomly:(1)the experimental group,12 rabbits (2)the control groups,12 rabbits(3)the recovery group 3 rabbits. The experimental group was altered functional loading (incisor trimming every three days, to ensure that no pulp exposed)after onset of anesthesia, for 2-8 weeks.3 rabbits were sacrificed at the end of the experiment,2,4,6,8 weeks. The recovery group:after 4 weeks stop incisor trimming, the rabbits were sacrificed at 8 weeks, the control group, only anesthesia, do not do any other treatment,3 rabbits were sacrificed at the end of the experiment, 2,4,6,8 weeks also, All the rabbits were given normal grain diet. So the altered functional loading animal model was established. The condyles,removed from all rabbits,were fixed with 10% neutral formalin at least 24 hours. Specimens were placed in 10% EDTA decalcification for 2 weeks (replaced once every two days decalcification solution). Until a pin that can easily pierce it. Fixed, decalcified, embedded tissue sections, stained with HE, investigate histological changes of condylar cartilage,subchondral bone and the thickness of condylar cartilage. The pictures of the condylar (the front, middle and back) was obtained under the Olympus optical microscope at 100 magnification. Use 0.2 mm diameter wire as a ruler, calibrated the scale in Image-Pro Plus 6.0 software, the distance between the the fiber layer and cortical endplate was measured in each part of condylar cartilage(3 times each part).ResultsCompared with the control group, the thickness of intermediate and posterior part of condylar cartilage was increased in the 2-week group (P<0.05), there was no significant change in the 4-week group; the thickness of anterior intermediate and posterior part of condylar cartilage was decrease in 6-week and 8-week group (P<0.05), the trabeculae of the subchondral bone was thin and the bone marrow cavity was widened. Compared with the control group, there was no significant change in the recovery group, the thickness of condylar cartilage was increased compared with the control group.Conclusion1. Altered loading can lead to the changes of condylar cartilage in thickness and histological changes in young rabbits, this method could established the altered functional loading model.2. In the recovery group, there was no significant difference between the control group, after stop incisor trimming, suggesting that the mandibular condylar has a strong ability to repair in young rabbits.3. Altered loading can lead to the remodeling of condylar in young rabbits.