• Estephan Jose Moana-Filho, Alberto Herrero Babiloni, and Aaron Nisley.
• Division of TMD and Orofacial Pain, School of Dentistry, University of Minnesota, Minneapolis, Minnesota, USA.
• J Oral Rehabil. 2019 Nov 1; 46 (11): 1009-1022.

BackgroundAbnormal endogenous pain modulation (EPM) was suggested as a pathophysiological characteristic of chronic pain. EPM has been investigated using psychophysical tests for pain facilitation and inhibition such as temporal summation of pain and conditioned pain modulation, respectively. Another psychophysical test for pain inhibition is offset analgesia (OA), where small variations in noxious stimulus intensity over time elicit a disproportionately large analgesic response. OA has been investigated in patients with mixed pain conditions, but not in chronic temporomandibular disorder (TMD) patients.ObjectiveTo compare OA responses in chronic TMD female cases to age-matched, pain-free female controls.MethodsOffset analgesia was assessed by applying noxious heat over the non-dominant forearm of chronic TMD cases (n = 22) and controls (n = 17), using a previously reported paradigm with individualised test temperatures (TT): T1(5 seconds) = TT, T2(5 seconds) = TT + 1°C and T3(20 seconds) = TT. Clinical and psychosocial characteristics were measured. Main outcomes for OA were delta computerised visual analogue scale (COVAS), per cent change (T2-T3/T2-T1) and area under the curve (AUC) ratio of pain ratings controlling for TT.ResultsNo statistically significant between-group differences were found for delta COVAS (TMD cases mean ± SD = 53.5 ± 22.0; controls = 51.6 ± 22.9, P = 0.876) and per cent change (T2-T3/T2-T1) (cases mean = 327.2 ± 375.1; controls = 226.9 ± 553.4, P = 0.515), with both groups presenting a robust OA response. TMD cases perceived more pain during OA trials than controls, as measured by AUC ratio (mean difference [95% CI] = -15.6 [-26.9, -3.5], P = 0.017).ConclusionChronic TMD cases presented with similar OA response over the forearm as controls; however, they experienced greater pain during testing. Future studies including this patient population should investigate OA responses over painful body sites, for example, jaw/face.© 2019 John Wiley & Sons Ltd.

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