Orthodontic movement; evaluation of periodontal ligament in a experimental study on adult Wistar rats

Objective: To assess the response of the periodontal ligament to a force applied in the initial phase of tooth movement. Methods: 48 male Wistar rats, were used in the present study. The rats were divided into four groups: control group without treatment (n=12) and three treatment groups (n = 12 per group) submitted to 50 g forces for periods of 24, 48 and 72 hours respectively. All the animals had free access to water and food. At the end of the experimental periods, the animals were given excess anesthetics and periodontium sections were analyzed by immunohistochemistry for proliferating cell nuclear antigen (PCNA). Results: Proliferation was observed in the periodontium of all the animals submitted to treatment, as assessed by PCNA expression. PCNA expression levels also revealed similar proliferation levels in the tension and in the pressure sides. PCNA-positive cells were detected at 24 hours, augmented at 48 hours and declined at 72 hours indicating the rapid onset of the repair process following injury. The cells marked for PCNA were visible throughout the evaluated areas, including the perivascular regions, enlightening the involvement of fibroblasts in the repair process. Conclusion: The results of the present study revealed that, even in adult animals, periodontal ligament cells respond quickly to the application of a force by increasing their proliferative activity in both the tension and pressure sides. (C) 2014 Sociedade Portuguesa de Estomatologia e Medicina Dentaria. Published by Elsevier Espana, S.L.U. All rights reserved.