Intraarticular pressure in the functioning human temporomandibular joint and its alteration by uniform elevation of the occlusal plane.

Intraarticular pressure (IAP) was measured at the posterior slope of the eminence in the upper compartment of the temporomandibular joint (TMJ) of 35 individuals (28 females and 7 males) under local anesthesia. Pressure measurements were obtained with the jaw in rest position, during maximal mouth opening (MMO), and while clenching. During MMO, IAP decreased to levels ranging between -130 and -5 mm Hg (mean, -53.82 +/- 34.40 mm Hg), whereas during clenching the pressure was always positive (range, +8 to +200 mm Hg; mean, 63.90 +/- 52.25 mm Hg). The significance of the fluctuating pressures with respect to the joint's maintenance and performance, as well as the potentially harmful effect of the positive pressure, especially when it is high and prolonged, are discussed. Females generated significantly higher pressures than males (73.70 +/- 61.06 mm Hg vs 31.42 +/- 11.47 mm Hg, P = .017). This gender difference regarding IAP may help elucidate the enigma of the considerably higher proportion of women with TMJ problems. In 22 of the patients IAP also was measured while clenching on a specifically constructed interocclusal appliance (IOA), which uniformly elevated the occlusal plane so as to reduce the force directed toward the TMJ. During clenching without the IOA, pressures ranged from 20 to 200 mm Hg (mean, 68.8 +/- 49.1), decreasing by 81.2% to IAP levels ranging from 0 to 40 mm Hg (mean, 7.9 +/- 10.9; P < .001) with the appliance in place. The use of an IOA as a palliative treatment for symptomatic TMJs is discussed.