ABSTRACT
The mechanisms of relief from persistent pain after temporomandibular joint (TMJ) surgery are not well studied. It was hypothesized that if persistent pain is relieved by TMJ surgery, up-regulated parts of the central nervous system will be desensitized and the neuroendocrine opioid release will decrease back to normal levels. Eleven female patients with a mean age of 47.4±19.4 years and with TMJ pain due to chronic closed lock were examined before and 6-24 months after TMJ discectomy. The effects on plasma ß-endorphin levels, pain intensity, and pain thresholds were analyzed. Plasma ß-endorphin levels (P=0.032), pain at rest (P=0.003), and movement-evoked pain (P=0.008) were all significantly reduced at follow-up. The reduction in plasma ß-endorphin levels correlated with a reduction in maximum pain intensity (P=0.024) and with a longer time after surgery (P=0.041). Seven out of eight patients who reported a substantial reduction in maximum pain intensity presented a decrease in ß-endorphin levels in the plasma. In conclusion, this pilot study showed a significant reduction in plasma ß-endorphin levels and pain intensity at 6-24 months after TMJ surgery; plasma ß-endorphin levels were correlated with time after surgery. However, the results must be interpreted with caution since this was a single-centre observational study with a small sample size. If replicated in larger sample sets, the measurement of ß-endorphin levels may be of prognostic value for the treatment outcome.
