The Effect Of Simulating Maxillary Protraction On The Position And Sutures Of Maxilla: An Experimental Study On SD Rats

Angle' s class Illmalocclusion is a kind of common dentofacial deformities in orthodontic practice, which can severely degrade the craniofacial development, oral function and facial aesthetics. Having complicated etiological mechanism, it is difficult to correct and should be pay more attention to. The maxillary protraction with orthopedic force is often used to treat those with the primary deformity of maxilla underdevelopment. But whether the maxillary protraction can promote the adaptive growth remodeling of maxilla, what its working biomechanism is, these questions are not solved yet presently, and the relative basic research is quite few. In our research, combined with the orthodontic clinic, the pubertal SD Rats were selected to establish the animal model for simulating maxillary protraction. And in this basis, the changes of the position and sutures of maxilla are investigated to explain what happened to the maxilla and the maxillary sutures with exerting orthopedic force on maxilla, to explore the working biomechanism of the maxillary protraction and provide partly theoretic basis for orthodontic practice.In this research, the pubertal five-week-old SD rats were chose as experimental object to establish the animal model for simulating maxillary protraction, on which was imposed the orthopedic force of 85g with utilizing the self-devised maxillary protraction appliance. Located lateral X-ray cephalograms were taken to measure and analyze the changes of maxillary development after exerting the orthopedic force for 4 weeks. The technique of immunohistochemistry was used to investigate theexpression of TGF- , in frontomaxillary sutures (FMS) and palatomaxillary sutures(PMS) with identical force performing for different extent of time. The average hue was selected as indicator, which was measured by the means of the analysis system of pathological color images. The measuring data were analyzed by the one-way ANOVA in software SPSS 11.0 version.The results are as follows: (1) With the imposing of orthopedic force of simulating maxillary protraction on maxilla, in the sagittal direction, the maxillary complex of the SD Rats in experimental group grows more quickly than that in two control groups, and the extent of the maxillary complex increases more evidently. The maxillary complex displays anti-clockwise forward and upward rotation. (2) With the imposing of orthopedic force on maxilla, upper incisors exhibit labial-inclined, labioclination of lower incisors changes insignificantly, and the shape and the dimension of skull are not affected significantly. (3) The expression of TGF-3 , in frontomaxillary sutures and palatomaxillary sutures shows different intensity in different extent of time. But The expression of TGF-{3, in experimental group is more intensive than that in two control groups, and that in operated control group and natural growth group has no significant difference. The results suggest that: In pubertal SD Rats, the orthopedic force for maxillary protraction can accelerate forward growth .promote the active remodeling of maxillary sutures; TGF- Piplays an important role in the remodeling of maxillary ' sutures. It also indicates that the animal model for simulating maxillary protraction established in this research can imitate precisely the maxillary protraction applying in the clinics, as haven' t been seen yet from the reports internally and internationally.