Effects Of Intermittent Dynamic Mandibular Advancement On The Expression Of Runx2and Collagen X In Condyle

Objective:Angle class Ⅱ malocclusion not only affects patients’ mastication, esthetics,the healthof temporomandibular joint,but also arouses psychological and societalproblems.Orthodontists are doing their best to seek for a new method,new technique toeffectivly,rapidly accelerate mandibular and TMJ growth and remodeling.In recentdecades,researchers have found that proper dynamic mechanical stimulation can promotecartilage and bone formation,but there were no research about the effect of dynamicmandibular advancement on endochondral ossification in condyle. As importanttranscriptional regulatory factors and markers in endochondral ossification,the expression ofRunx2and collagen X can reflectthe growth and remodeling of TMJ,therefore,our studywill investigate the effects of intermittent dynamic mandibular advancement on theexpression of Runx2and collagen X incondyle.Method:In our study,twenty-eight male35-day-old wistar rats were randomly divided into threeexperimental and one control groups.The three experimental groups receivedynamic,static,and functional mandibular advancement respectively.At the beginning of theexperiment,we set up “dynamic,static,functional mandibular advancement model”firstly.Then the rats in dynamic and static groups receive dynamic(0.5Hz) and staticmandibular advncement1hour a day,according to their groups.The rats in functionalmandibular advancement group subject to functional stimulation24hours a day,and rats incontrol group do not receive any mandibular advancement stimulation.After2weeks ofexperiment,the rats were sacrificed,the tissues were fixed, decalcified, embedded in paraffin,serial sections were cut through the TMJ in the sagittal plane.And the sections were preparedfor immunohistochemistry staining.Expression of Runx2and collagen X weresemi-quantitatively evaluated by means of software Image-Pro Plus6.0.The data obtainedwas analysed by software SPSS17.0(Chinese).A student t-test and ANCOVA were applied toexamine the intergroup differences for measurements, respectively. Results:The number of cells and area expressing Runx2and collagen X among the four groupsshow significant different, P＜0.001.1. The number of cells expressing Runx2in dynamic group was higher than that ofstatic group, P＜0.01; the number of cells expressing Runx2in dynamic group and controlgroup were higher than that of functional group, P＜0.001;the number of cells expressingRunx2in static group was lower than that of control group,but higher than functionalgroup,P＜0.05.2. The area expressing Runx2in dynamic group and cortrol group were larger than thatof static group, P＜0.001;the area expressing Runx2in dynamic group, static group andcontrol group were larger than that of functional group, P＜0.001or P＜0.01.3. The area expressing collagen X in dynamic group, static group and cortrol groupwere larger than that of functional group, P＜0.001; the area expressing collagen X indynamic group were larger than that of control group and static group, P＜0.001.Conclusion:1. Different modes and duration of mandibular advancement differently regulated theexpression of Runx2and collagen X in condylar chondrocytes.2. In comparation with static mandibular advancement (static group,functional group),dynamic mandibular advancement (dynamic group) can significantly increase the expressionof Runx2and collagen X in condyle.3. In comparation to continuous mandibular advancement (functional group),intermittent mandibular advancement (dynamic group, static group) can significantlyincrease the expression of Runx2and collagen X in condyle.