Histological Evaluation of Mandibular Condyle after Jaw Protrusive Stimulation in Rats

Objective: The present study aimed to evaluate the cytological and histological behavior of the condyle of rats after mandibular advancement.

Materials and Methods: Thirty male Holtzman rats were randomly divided into three experimental and three control groups, with five animals each, aged five, nine, and thirteen weeks. The animals received flat tracks on the upper and lower incisors made of photopolymerizable composite resin, which resulted in the protrusion of the mandible. After thirty days, the animals were euthanized, the mandibles were dissected and photographed, the condyles were demineralized, paraffinized, sectioned, and stained in H&E. Cytological and histological analysis were performed using a light microscope. The collected data were tabulated using the SPSS 17.0 for Windows software and the Student's “t” test was used to compare the data.

Results: In the experimental group there was an increase in the number of cells in the proliferative layer and the mandibular size in five-week rats; increased number of fibrous layer cells in nine-week-old rats; and an increase in the proliferative layer in thirteen-week-old rats.

Conclusion: The protrusion of the mandible in rats of five, nine, and thirteen weeks of age promoted an increase in cell and area in different layers of the condyle. However, further studies are needed to better understand the adaptive responses generated in the condyle resulting from functional orthopedic stimuli.