Abstract
BackgroundClinical differentiation between pain mechanisms of temporomandibular joint (TMJ) arthralgia and osteoarthritis (OA) is challenging. The aims were to compare somatosensory function at the TMJs and conditioned pain modulation (CPM) effects between TMJ arthralgia and OA patients diagnosed clinically and based on different imaging techniques and age- and gender-matched healthy controls (n = 41).MethodsPatients (n = 58) underwent standard clinical examination and three different TMJ imaging modalities. After each examination, they were classified into arthralgia or OA based on the findings. TMJ region somatosensory testing was performed in all participants. Z-scores were calculated for patients based on healthy reference data. CPM was tested by comparing pressure pain thresholds (PPTs) at TMJ and thenar (control) before, during and after the application of painful and nonpainful cold stimuli. Data were analyzed using analyses of variance.ResultsSomatosensory abnormalities were commonly detected in both patient groups. Assessment of somatosensory function at the TMJ revealed that arthralgia patients were less sensitive to warmth, cold and tactile stimuli than OA patients (P < 0.048). OA patients showed pressure hyperalgesia compared with arthralgia patients (P = 0.025). There was a significant CPM effect at both test sites during painful cold application in all groups (P < 0.001). There was no significant difference in the relative CPM effect between groups except for clinically diagnosed arthralgia patients showing reduced CPM effect compared with controls (P = 0.047).ConclusionsPain profiles including somatosensory function differed between TMJ arthralgia and OA patients although CPM effects were similar in patients and controls. Thus, different TMJ pain conditions may share common pain mechanisms but the present study for the first time also indicated that differential pain mechanisms could be involved.Electronic supplementary materialThe online version of this article (doi:10.1186/s10194-016-0653-6) contains supplementary material, which is available to authorized users.
Highlights
Clinical differentiation between pain mechanisms of temporomandibular joint (TMJ) arthralgia and osteoarthritis (OA) is challenging
All the included TMD pain patients were classified as 28 TMJ arthralgia and 30 TMJ OA based on clinical examination plus Cone beam computed tomography (CBCT) findings
The assessment of sensory and pain thresholds using a standardized quantitative sensory testing (QST) protocol uncovered an array of somatosensory abnormalities in both TMJ arthralgia and OA patients diagnosed clinically and based on different imaging modalities
Summary
Clinical differentiation between pain mechanisms of temporomandibular joint (TMJ) arthralgia and osteoarthritis (OA) is challenging. TMJ OA involves pain in the TMJ associated with inflammation and degenerative processes of the bony components revealed by imaging techniques or coarse crepitation [4]. These criteria are internationally accepted, have been shown to be reliable, and recently have been updated to the Diagnostic Criteria for TMD (DC/TMD) [5,6,7], there are still major concerns about how to differentiate between the involved pain mechanisms in TMJ arthralgia and OA. A good understanding of underlying pain mechanisms may have significant implications for the rational management of pain and dysfunction
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