Temporomandibular synovial fluid pressure response to altered mandibular positions

Hydrostatic synovial fluid pressure within the superior aspect of the temporomandibular joint space of the growing pig, Sus scrofa domesticus, was examined in response to various acute and chronic alterations of mandibular position. Bilateral measurements of pressure were recorded with chronically implanted wick catheters in three 8-week-old pigs before and at the time of appliance placement and then at 2-day intervals until the animals were 20 weeks old. Besides confirming the observations of a previous study, we noted that forward positioning of the mandible caused an increase in synovial fluid pressure that decayed to baseline levels within 2 hours. Posterior positioning of the mandible effected a larger increase in pressure that partially decayed over 2 hours but did not return to baseline levels over the entire course of the experiment. These results may have significance in the understanding of the physiology of the temporomandibular joint, local control mechanisms involved in the normal and treatment-aided growth of the mandible, and disorders of the temporomandibular joint.