Expression of RANKL mRNA during Root Resorption Induced by Orthodontic Tooth Movement in Rats

Receptor activator for nuclear factor kappa b ligand (rankl), which is alsocalled osteoclast differentiation factor, is an important regulatory factor in osteoclastmaturation. knowledge of bone and cementum similarities and rankl role in bone resorptionsuggests the possibility of a role for this protein in root resorption induced by orthodontictooth movement. the aim of this study is to examine the expression of ranklmrna during root resorption induced by orthodontic tooth movement in rats.materials and methods: in order to move maxillary right first molars mesially fixed ni-ticlosed coil springs (dentaurum®-germany) were tightened to the teeth. sample consistedof 20 male seven week old wistar rats. for each animal, the contralateral tooth was usedas, an internal control. at day 21 the rats were sacrificed. tissues from 10 rats were embeddedin paraffin for histologic examination. scratched material from resorptive lacunaeon mesial sides of the roots of the other ten rats was used for extracting mrna by rtpcr.results: the histologic sections, analyzed histomorphometrically, showed a significantincrease in root resorption in the case group as compared to the control (p<0.001).densitometric studies of rankl mrna expression band on gel electrophoresis showedsignificantly increased rankl expression in the resorptive lacunae of the case group(p<0.001).conclusion: this observation indicates increased rankl expression is associated withorthodontic tooth movement induced root resorption.