Effects Of Ultrasound On Cementum Repair After Orthdontic Root Resorption In Rats And Related Mechanism

Objective: To study the effect of ultrasound on cementum repair and theexpressions of TGF-β1and OPG/RANKL ratios in the model of root resorption in rats.Methods:64healthy male Wistar rats were established as animal models oforthodontic root resorption, and randomly divided into four groups(the control group,experimental group, natural recovery group, ultrasound repair group) with16in eachgroup. The ultrasound repair group were given1.5MHz100MW/cm2ultrasoundirradiation for15min per day in the two weeks of repair period. Rats in each group wererandomly divided into two groups(n=8), in one group scanning electron microscopy wasused to observe the root surface absorption condition and the root resorption indexeswere measured, in the other group, upper first molar-centered mesial-distal tissue sliceswere generated from the upper first molars and peridentium. Specimen slices wereanalyzed with TGF-β1,OPG, RANKL, immunohistochemistry, and optical microscopy.Analyses of cell number, densitometry, and one-way analysis of variance wereperformed.Results:1. Large amounts of new cementum formation were observed in ultrasound repairgroup. The root resorption index of ultrasound repair group was significantly lower thanthe natural repair group (p<0.05). There was no significant difference between theexperimental group and the natural recovery group.2. The expressions of TGF-β1and OPG/RANKL in ultrasound repair group weresignificantly increased than the natural repair group (p<0.01).Conclusion: Ultrasound promoted the repair and the reconstruction of thecementum by increasing the expressions of TGF-β1and OPG/RANKL ratios.