Effects Of Intermittent Dynamic Mandibular Advancement On The Expression Of Sox9and Collagen â…¡ In Condyle

Objective: The incidence of AngleⅡ malocclusion accounts for30%ofpatients with treatment. These usually affect patients’ mastication, esthetics,even arouses psychological problems. At present, we often use functionalappliance to treat AngleⅡ malocclusion in clinical. However, there are variousdisadvantages such as increasing the suffering of patients, the uncertainefficacy. Therefore, orthodontists are doing their best to seek for a moreeffective and rapid new method to accelerate TMJ remodeling. In recentdecades, some studies have shown that proper dynamic mechanical stimulationcan promote mesenchymal stem cells different into chondrocytes、increaseextracellular matrix synthesis and accelerate chondrocytes proliferation. Asimportant transcriptional regulatory factors and markers in chondrocyteproliferation and differentiation, the expression of Sox9and CollagenⅡcanreflect the growth and remolding of condylar cartilage. The purpose of thisstudy was to investigate the effect of intermittent dynamic tensile on theexpression of Sox9and CollagenⅡ in growing condyle.Method: Twenty-eight male35-day-old Wistar rats were randomlydivided into four groups (Dynamic group, Static group, Functional group andControl group, n=7). The rats in dynamic and static groups receive dynamicand static tensile60min everyday, frequency0.5Hz and0Hz respectively. Therats in functional group subject to functional stimulation24hours everyday,and rats in control group do not receive any stimulation. After2weeks ofexperiment, dissect rats’ head to collect bilateral temporomandibular, removethe soft tissue as much as possible, Paraffin-embedded after conventional fixedand decalcification. The sections were prepared for immunohistochemistry staining. The expression of Sox9and collagenⅡ were semi-quantitativeevaluated by Image-Pro Plus6.0. Then use ANOVA-LSD to analyze the data bySPSS for windows (Version17.0SPSS Inc).Results:1、The number of cells expressing Sox9in dynamic group andfunctional group was higher than that of control group, P<0.001; Comparethese measurements in static group to control group, there are no significantdifference; The number of cells expressing Sox9in dynamic group is higherthan that of static group, P<0.001.2、The area expressing Sox9in dynamic group was higher than that ofcontrol group, P＜0.01; The area expressing Sox9in functional group andstatic group was lower than that of control, but there was no statistic difference;The area expressing Sox9in dynamic group was higher than that of static group,P<0.001.3、The area expressing CollagenⅡ in dynamic group and functional groupwas higher than that of control group, P＜0.001; The area expressing collagenⅡin static group was higher than that of control, but there was no statisticdifference; The area expressing CollagenⅡ in dynamic group was higher thanthat of static group, P<0.001.Conclusion:1. After2weeks, short-term intermittent dynamic mandi-bular advancement can significantly increase the expression of Sox9andCollagenⅡ in condyle, which suggests that intermittent dynamic mandibularadvancement can increase chondrocyte proliferation and the adaptiveremolding of TMJ.2. The effect of short-term intermittent static tensile is not evidencecompared with control group. Therefore, the effect needs to be furtherinvestigated. 3. Function appliance can significantly increase the thickness of condylecartilage、the number of cells expressing Sox9and the expression of CollagenⅡ, which suggests that function appliance can enhance condylar proliferation.