title: Reduction in maximum pain after surgery in temporomandibular joint patients is associated with decreased beta-endorphin levels - a pilot study.
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 β-endorphin levels, pain intensity, and pain thresholds were analyzed. Plasma β-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 β-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 β-endorphin levels in the plasma. In conclusion, this pilot study showed a significant reduction in plasma β-endorphin levels and pain intensity at 6-24 months after TMJ surgery; plasma β-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 β-endorphin levels may be of prognostic value for the treatment outcome.
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden. Electronic address: anna.feldreich@ki.se.
authors.forename: A
authors.initials: A
authors.lastname: Feldreich
authors.affiliation: Section of Orofacial Pain and Jaw Function and Scandinavian Centre for Orofacial Neurosciences (SCON), Karolinska Institutet, Huddinge, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Ernberg
authors.affiliation: Department of Clinical Dentistry, Division of Oral Surgery and Oral Medicine, University of Bergen, Bergen, Norway.
authors.forename: A
authors.initials: A
authors.lastname: Rosén
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005157:Facial Pain / Q000097:blood* / Q000601:surgery*; D005260:Female; D006801:Humans; D008875:Middle Aged; D059408:Pain Management / Q000379:methods*; D010147:Pain Measurement; D017288:Pain Threshold; D010865:Pilot Projects; D011446:Prospective Studies; D011862:Radiography, Panoramic; D013705:Temporomandibular Joint Disorders / Q000601:surgery*; D016896:Treatment Outcome; D001615:beta-Endorphin / Q000097:blood*
chemical_list: D001615:beta-Endorphin
keywords: beta-endorphin; central sensitization; discectomy; pain intensity