Method: Forty adult (200-225 g) male Sprague Dawley rats were used in this study. Ten were injected with complete Freund’s adjuvant (CFA, 50 mg in 50 ml of paraffin oil) into the superior joint space of the TMJ to induce acute inflammation (CFA only group). Ten additional rats also received CFA injection in addition to subcutaneous implantation of the microstimulatory device lateral to the TMJ (CFA + MS). An additional ten rats received microstimulators only (MS). Microstimulation was performed for 30 minutes twice daily. The rats were sacrificed 48 hours later along with ten age-matched, uninjected controls (Con). TMJ tissues and trigeminal ganglia (TG) were removed, homogenized, and analyzed via ELISA for changes in levels of TNF-α and IL-1β.
Result: ELISA analysis revealed a significant increase in TNF-α and IL-1β levels in the CFA group in comparison to the uninjected Con group in both the TMJ and TG (p<0.01). The CFA + MS group produced a significant reduction in both TNF-α and IL-1β in the TMJ tissues (p<0.01), while levels in the TG were only slightly decreased (p<0.07) relative to the controls.
This study demonstrated that adjuvant-induced inflammation of the TMJ resulted in an increase in proinflammatory cytokine levels during the acute stage of inflammation of the TMJ. These levels were decreased with the use of the microstimulatory device, suggesting that with further testing it may have potential as a therapeutic device. This study was supported by the Baylor Oral Health Foundation.
Keywords: Inflammation, Inflammatory mediators, Neuroscience and TMJ and masticatory muscles