Changes in condylar cartilage after anterior mandibular displacement in juvenile pigs

Abstract

Adaptive remodelling of the mandibular condyle in response to mandibular advancement is the mechanism exploited by orthodontic forward displacement devices. Objective: This work investigated the expression of collagens, matrix metalloproteinases and vascular endothelial growth factor during this process. Design: Twenty juvenile pigs were randomly divided into two experimental groups, where the treatment group was fitted with mandibular advancement splints, and the control group was not. Changes in the mRNA content of condylar cartilage tissue was then were measured by real-time PCR using specific primers after 4 weeks of treatment. Results: The temporal pattern of the expression of Col1 and MMP13 during condylar adaptation coincided with that during natural condylar growth. The amount of the expression of Col10 during condylar adaptation was significantly lower ( p < 0.05), whereas the expression of Col2, MMP8 and VEGF was significantly higher compared to natural growth ( p < 0.05). Conclusions: It is suggested that condylar adaptation in growing pigs triggered by mandibular forward positioning results not only from passive adaptation of cartilage, but also involves growth affected processes. Our results showed that mechanical strain produced by mandibular advancement induced remodelling and revascularization in the posteriocranial mandibular condyle. These results are mostly consistent with former published histological and histomorphometrical analyses.