Insulin-like Growth Factor-1 Expressed During The Orthodontic In Rat

As the rapid development of today's society, improvement of people's living standards, more and more people choose to make themself more perfect image by Orthodontic treatment. Tooth movement in the course of orthodontic is a complex physiological process, when the teeth under mechanical force, osteoblasts , osteoclasts and macrophages interact and constrain each other, and release a variety of cytokines to activate, enhance or inhibit the activity of various cells to led periodontal tissues to alterate, including the bone resorption of pressure side and the bone regeneration of tension side. the research of bone's biological behaviour change under particular mechanical stress and mechanism of cytokines interact become a frontline question in international oral medicine domain .In 1978, scientists first time discovered insulin-like growth factor-I in human plasma. Later they can nearly find IGF- I in all types of organizations, and it is one of most abundant growth factors in bone. Its main function is to regulate the growth of the body after the birth, and promote many cell lines to mitosis, including keratinocytes , osteoblasts, smooth muscle and skeletal muscle cells.IGFs gene expression mainly in the liver, the synthesis and secretion control by growth hormone (GH) levels in the blood , the secretion of GH is controlled by IGFs negative feedback regulation, thereby form a regulated hormone-axis system, we called growth hormone -- insulin-like growth factor axis units (GH-IGF axis). IGFs not only exist in the blood circulation as endocrine factors, but also play a role in the local organization through the secretion of autocrine and paracrine, especially important in bone metabolism regulating course.It is very important sense to clinical work that studying the mechanism of orthodontic tooth movement and how to speed up the process of orthodontic tooth movement. The control of the power size, time, direction is clinical orthodontic doctors most need to care about. There is not a report about IGF-I expression in normal periodontal tissues and periodontal tissue of the comparative analysis of IGF-I expression in the process of tooth movement under different loading forces.The purpose of this study is detect IGF-I expression in periodontal tissue cells at different times after under different loading forces by immunohistochemical method, to explore the periodontal tissues rebuiled function of IGF- I in the process of orthodontic tooth movement, in order to further elaborate the mechanism of orthodontic tooth movement, and comparative analyze appropriate force size, time in the clinical treatment to improve the efficiency of clinical treatment, safety, and provide a theoretical basis.Materials and Methods: 33 Wistar rats were randomly divided into 6 groups, unloaded group, loaded 1 day group, loaded 4-day group, loaded 7 days group, loaded 14 days group and loaded 21 days groups of six. In addition to unloaded group, each of three load force 40g, the other three load strength 100g.Use rats maxillary incisor teeth as anchorage to pull maxillary first molar to mesial side. Get maxillary first molar and its periodontal tissue, by 4% paraformaldehyde fixed and 10% EDTA decalcification, product tissue slice that maxillary first molar as the center ,and HE stain line and IGF-I immunohistochemical staining, TRAP staining. Detect the respective expression of IGF-1 in tension and pressure side of first molar . take tissue slice to semi-quantitative analysis Combined with time of tooth movement will be carried out. On the base of tissue slice histological observation and image analysis , count IGF-I immunohistochemistry percentage of positive cells for statistical analysis.Results: In normal periodontal tissues, IGF-I expression, only a small amount, distributed in the periodontal tissue cells within the cytoplasm. IGF- I expression from 1 day to 7 days gradually increased in Experimental animals'tension side, the peak period is 7 days and then gradually decline , maintain at a higher level than normal periodontal tissue ; IGF-I expression from 1 day to 14 days gradually increased in Experimental animals'pressure side, then gradually decreased, the peak period is 14 days. Compared to the same period , the number of positive cells in 100g group is more than 40g group. From histological observation we can also find osteoclasts appeared earlier in the 100g group , alveolar bone and root surface absorbed more serious in 100g group's pressure side.CONCLUSION:â‘ The experimental results show that the insulin-like growth factor-I participate in periodontal tissue reconstruction during orthodontic process, and its higher expression in the periodontal tissue can be considered to be active periodontal alterations performance.â‘¡there is a relationship between loading time and the expression of IGF-I in the periodontal tissue reconstruction.â‘¢The most suitable strength in the experimental rats tooth movement is 40g.â‘£the interval time should be longer than 21 days. Further research that the best strength and interval time in human dental treatment is needed.