Mandibular condyle changes in rats with unilateral masticatory function

Certain malocclusions or unilateral tooth loss can lead to asymmetric functional load of the two mandibular sides during mastication and induce skeletal asymmetries to the condylar process of growing individuals. However, in adults, asymmetric function may have a different impact. The aim of the present study was to investigate three-dimensionally the effects of unilateral masticatory function on the condylar process morphology in growing and adult rats and the adaptive processes to differential condylar loading.

Fifty-six growing and adult Wistar rats aged 4 and 26 weeks respectively were obtained. The maxillary right molars of the experimental animals were extracted and all animals were followed for 12 weeks. Three-dimensional images were obtained by an in-vivo microcomputed tomography (micro-CT) examination. The following measurements were studied: condylar process height, condylar base width, and condylar cross-sectional surface.

While no differences were found with regards to condylar process height and base width, the cross-section of the condyle on the extraction side did not increase during growth in the young rats. No such differences were found in adults. Young rats had statistically significantly shorter condylar height, base width and cross-sectional surface than the adult rats and showed significant growth of these structures during the experimental period.

Condylar height and base width growth are not hindered by reduced occlusal function, contrary to the average cross-sectional surface, which implies that the condyle form of growing individuals becomes thinner while maintaining its length, in the absence of occlusal stimuli. The condyle of adult rats with extractions is less affected by occlusion changes.