Occlusal stimuli influence on the expression of IGF-1 and the IGF-1 receptor in the rat periodontal ligament

Objective: To test the hypothesis that hypofunction/recovered occlusal function has no effect on the changes in insulin-like growth factor-1 (IGF-1) and IGF-1 receptor expressions and cell proliferation of periodontal ligament (PDL) cells. Materials and Methods: To produce occlusal hypofunction, the appliances were attached to the rats' maxillary and mandibular incisors. Subsequently, occlusal contact of the molar area was thoroughly recovered by removal of the appliances. Results: In periodontal sections, localization of IGF-1, the IGF-1 receptor, and proliferating cell nuclear antigen (PCNA) immunoreactive cells was significantly more expressed in the control group compared with the hypofunctional group (P <.01). In addition, after the recovery of the occlusion, IGF-1, IGF-1 receptor, and PCNA were detected significantly much more than in the hypofunction group (P <.01). Conclusion: The hypothesis was rejected. This study suggests that occlusal stimuli induce cell proliferation of PDL cells by increasing IGF-1 and IGF-1 receptor expression.