| How to inhibit residual ridge resorption (RRR) has puzzled prosthetic researchers for a long time. The loss of the bone will influence the retention and stabilization of the denture. Many researchers had studied the etiopathogenisis, prevention and cure methods of RRR and tried to find an effective way to prevention and cure it. However, the studies had not drawn a conclusion about how to inhibit RRR due to the limit of animal model and clinical research methods.Now, researchers are searching for an effective way to reduce RRR after teeth extraction, which include imbedding hydroxyapatite artificial bone, coral artificial bone, autogenous bone and bone from outside. The capability of bone formation is very low if we only imbed bone marrow or bone marrow cell. The main reasons are lack of cell vector, bone marrow is prone to run off or absorbed, cannot reach the cell density that needed and low resistance to infection. Imbed the autogenous bone will increase the trauma and little patients tend to accept. It is possible to utilize hydroxyapatite as bone marrow cell vector. But as non-degradation material, hydroxyapatite cannot substitute completely by newly formed bone and the biological character is not coincidence with the original bone. As a result, the methods above are dying out now. Recently, more and more researchers concentrate on molecular organism materials and histio-organism materials. The ADM used in our experiment is a histio-organism material. The three diamensions framework of ADM can provide a satisfactory supporter for the regeneration of tissue cells and the ecto-cell matrix protein can promote the adhesion and proliferation of epidermic cells. And also, it can guide the growth of osteoblast, accelerate thebone formation and prevent RRR. ADM can effectively ensure the allocation accuracy of the regeneration cell and keep the tissue renovation in order. Studies have shown that ADM has a good biocompatibility. It can accelerate the healing after teeth extraction and has a positive role in reducing RRR.Studies on healing and reconstruction of rat residual ridge have shown that the resorption curve of rat is resembled to human in shape. And the difference is the healing period is about 4 weeks, which is shorter than human. Our experiment is to investigate the inhibit role of ADM in alveolar bone resorption through plugging ADM after tooth extraction. And at the same time, we detected the number of TRAP positive cells and BMP-2 expression level in alveolar bone, which will provide a powerful evidence for further study on inhibiting residual ridge resorption.The 70 healthy 15 weeks male Wister rats were allotted at random into two groups, experimental group and control group. One of the central incisors in mandible was extracted. And the rats in both groups were perfused and sacrificed at 3rd day, 7th day, 14th day, 21st day, 28th day, 35th day. Histological section in the alveolar crest of central incisors region were prepared, then proceeded with HE staining, TRAP staining and BMP-2immunohistochemical staining. Observing the histological changes, TRAP positive cells number and BMP-2 expression level of the alveolar bone in each group, and then mark the RRR degree. Analyze the histological sections with semi-quantitie. Count the number of TRAP positive cells on the basis of histological observation and image analysis. The gray scale integral of BMP-2 expressing image were treated by statistic.The results shown that there was no significant change in epithelium and lamina propria during the whole experiment period in the control group(without any wadding). And there was no obvious bone resorption in 3rd day group and became obvious in 7th day, 14th day, 21st day, 28th day groups. The bone resorption tended to stable in 35th day group. The number of TRAP positive cells changed with the activity of bone resorption. The BMP-2 staining intensity changed with the activity of bone formation and located in cytoplasm and cell membrane. BMP-2 mainly expressed in a small quantity of fibroblast of lamina propria and osteoblast in the surface of bone and was well distributed. The whole process of bone resorption resembles that of human. There was no obvious bone resorption in 3rd day group of experimental (plugging ADM immediately after tooth extraction) and TRAP positive cell was rare. There was no obvious change in BMP-2 staining intensity between experimental group and control group. They concentrated mainly in a small quantity of fibroblast of lamina propria, which near to the surface of alveolar bone and osteoblast in the surface and cavitas medullaris of bone. We found bone resorption lacune in 7th day, 14th day, 21st day, 28th day groups and polynuclear osteoclast in the lacune. There are strong stained particles located in cytoplasm and cell membrane of TRAP positive cells. BMP-2 still expressed in a small quantity of fibroblast and osteoblast in the surface of bone, and also can be seen in osteoblast and hemopoietic stem cells in cavitas medullaris of alveolar bone. The number of TRAP positive cells and the intensity of BMP-2 staining are obviously higher than the control group. The bone resorption tended to stable in 35th day group and then the structure of bone resembled to the control group. The TRAP positive cells were found occasionally and the intensity of BMP-2 staining was resembled to the control group.In the experimental group, after plugging ADM, there was an active boneresorption after tooth extraction in 7th day, 14th day, 21st day, 28th day groups. The ADM in alveolar socket can guide the growth of osteoblast effectively and promote the formation of bone. It can prevent the resorption and atrophy of alveolar bone and inhibit RRR. The number of TRAP positive cells and the intensity of BMP-2 staining were higher than the control group obviously. The bone resorption tended to stable in 35th day group, and there were no obvious change in the descent of the number of TRAP positive cells and the intensity of BMP-2 staining in both group.In this study, we established an animal model successfully on studying the patho-physiology mechanism, prevention and cure methods of alveolar bone resorption after tooth extraction of rats. The results shown that plug ADM in alveolar socket after tooth extraction can inhibit RRR effectively. BMP-2 expressed in fibroblast and osteoblast in the surface of alveolar bone, and the content and intensity were related to the activity of bone formation. The results demonstrated that the expression of BMP-2 is an effective index in judging bone formation. Since plugging ADM immediately after tooth extraction can inhibit RRR effectively, it set a powerful experimental basis for clinical application in the future.
|
PDF Full Text Request