Expression Of RANKL/OPG In PTH-accelerated Orthodontic Tooth Movement After Mandibular Ramus Osteotomy

Introduction:This study investigated the effects of different doses of parathyroid hormone(PTH)on orthodontic tooth movement after mandibular ramus osteotomy and the associated dose-response relationship.Methods:One-hundred and twenty rabbits were divided into two experimental groups(A and B)and two control groups(control group and negative control group).An experimental model of mandibular ramus osteotomy with installation of an orthodontic tooth movement device was established in groups A and B and the control group.Postoperatively,groups A and B received intermittent subcutaneous injections of PTH 20 and 40 μg/kg,respectively,and the control group received injections of normal saline.The negative control group underwent installation of the orthodontic tooth movement device without mandibular ramus osteotomy and received normal saline postoperatively.Changes in expression of RANKL.OPG and RUNX2 in the periodontal tissues of the first molars were evaluated by immunohistochemical analysis and quantitative fluorescence polymerase chain reaction.Results:Movement of the first molars was more rapid in group B than in group A in the 21 days postoperatively.Significantly higher RANKL mRNA levels and lower OPG、RUNX2 mRNA levels were detected on the compression side of the periodontal tissues in groups A and B than in the control groups.There was a significant difference in RANKL、OPG and RUNX2 expression levels between group B and the control groups at all time points.Conclusions:Mandibular ramus osteotomy and high-dose PTH act synergistically to increase catabolism on the compressed periodontal tissues,thereby accelerating remodeling of periodontal bone and promoting orthodontic tooth movement postoperatively.