Methods: Fortynine patients with TMJ involvement of rheumatoid arthritis were included. TMJ resting pain, tenderness to palpation, pressure pain threshold over the TMJ and the reference site glabella, pain upon mandibular movement and anterior open bite (0 - 9) were assessed. Plasma samples were obtained for analysis of TNFa, sTNFrII and inflammatory markers and the patients were grouped according to higher (n = 25) or lower (n = 24) plasma TNFa concentrations.
Results: The median (IQR) plasma TNFa and sTNFrII concentrations were 9.8 (3.7) and 2070 (732) pg/mL, respectively, in the patients with lower plasma TNFa and 22 (14) and 2809 (1404) pg/mL in the patients with higher plasma TNFa. There was a higher ratio between sTNFrII and TNFa plasma concentrations in patients with lower than in patients with higher plasma TNFa (p < 0.001). Presence of anterior open bite was found in 54% of the patients with low plasma TNFa and in 52% of the patients with high TNFa. The median (IQR) degree of anterior open bite (median ± IQR) was 1 (4) in both of these patient groups.
There was a negative correlation between plasma sTNFrII concentration and degree of anterior open bite in the patients with lower plasma TNFa (rs = -0.41, p = 0.044).
Conclusion: High plasma levels of sTNFrII in rheumatoid arthritis patients with lower plasma levels of TNFa seem to prevent or reduce TMJ cartilage and bone destruction in RA by inhibiting TNFa effects.