Up-regulation of various cytokines in pulp tissues after experimental tooth movement in rats

Aim: Previous studies have demonstrated that orthodontic forces may injure dental pulp tissue via the apical foramen. The purpose of this study was to investigate the expression of various cytokines in pulp tissues of root apex after orthodontic tooth movement and compare the amount of internal root resorption in vital and pulp less rat teeth. Methods: Upper right first molars of 7-week Wistar rats were subjected to pulpectomy and root canal filling. Both upper first molars were moved medially for 28 days (10 and 50 g force). The amount of internal root resorption and number of TRAP positive cells around the root apex were determined and expression of Interleukin-1β (IL-1β), Tumor Necrosis Factor-α (TNF-α), Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL) and Macrophage Colony-Stimulating Factor (M-CSF) in pulp tissue of root apex was examined by immunohistochemistry. Results: The expression of these factors in 50 g force groups was significantly higher in vital tooth than in the 10 g groups. However, expression of these factors was not detected in the control group. The number of odontoclasts around root apex in vital teeth was significantly more than in the pulpectomized teeth (p<0.05). The number of odontoclasts and the amount of internal root resorption in vital teeth were significantly more than in pulpectomized teeth (p<0.05). Conclusions: This study demonstrates that during orthodontic tooth movement, injured pulp cells express these bones resorbing cytokines; as a result, internal apical root resorption may occur because of derived odontoclasts.