Interleukin-1alpha and tumor necrosis factor-alpha expression during the early phases of orthodontic tooth movement in rats.

Remodelling of the periodontium after application of mechanical forces constitutes the basis of clinical orthodontics and various immunoregulatory molecules are involved in this process. The aim of this study was to investigate the expression of the cytokines interleukin-1alpha (IL-1alpha) and tumor necrosis factor-alpha (TNF-alpha) in dental tissues during the early phases of orthodontic tooth movement. Eightteen male Wistar rats were used. All maxillary right first molars were moved orthodontically, with a force of 0.5 N, for 3 h, 1 d, and 3 d. The contralateral sides served as untreated controls. Parasagittal sections of the maxillary molars and the surrounding tissues were subjected to immunohistochemical staining for IL-1alpha or TNF-alpha, and were evaluated with light microscopy. IL-1alpha and TNF-alpha were expressed in the bone and periodontal ligament (PDL) along the roots of the orthodontically moved molars and in the gingiva. Increased expression of both cytokines was observed in the aforementioned areas after 1 and 3 d of tooth movement. The pulp tissue exhibited only minor changes in cytokine expression during tooth movement. The results suggest that mechanical stress results in almost immediate inflammatory reactions in various dental tissues.