Jaw muscle and joint psychophysics—relevance for clinical orofacial pain practice and research. A narrative review

Diagnosis of jaw muscle and temporomandibular joint (TMJ) pain has been greatly standardized with the development and implementation of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD). A significant part of the DC/TMD examination—pain on palpation and jaw movements—relies on psychophysical principles in the clinical procedures. Thus, it is essential that examiners are aware of the strengths and limitations of such techniques. Here we first review the background and psychophysical techniques used in the clinic and then discuss opportunities to apply both simple and more advanced modifications in research settings to further understand musculoskeletal pain mechanisms and signatures. The goal is to facilitate development of individualized treatment and precision medicine for which a good starting point seems to be careful pain phenotyping where psychophysical testing may play a substantial role.

Orofacial pain; Temporomandibular disorders; Psychophysics; Neuroscience; Pain assessment; Narrative review

[1] Häggman-Henrikson B, Liv P, Ilgunas A, Visscher CM, Lobbezoo F, Durham J, et al. Increasing gender differences in the prevalence and chronification of orofacial pain in the population. Pain. 2020; 161: 1768–1775.

[2] Felin GC, Tagliari CVDC, Agostini BA, Collares K. Prevalence of psychological disorders in patients with temporomandibular disorders: a systematic review and meta-analysis. Journal of Prosthetic Dentistry. 2024; 132: 392–401.

[3] AlSahman L, AlBagieh H, AlSahman R. Oral health-related quality of life in temporomandibular disorder patients and healthy subjects-a systematic review and meta-analysis. Diagnostics. 2024; 14: 2183.

[4] Vallin S, Liv P, Häggman-Henrikson B, Visscher CM, Lobbezoo F, Lövgren A. Temporomandibular disorder pain is associated with increased sick leave and reduced health related quality of life. European Journal of Pain. 2024; 28: 1827–1840.

[5] Schiffman E, Ohrbach R, Truelove E, Look J, Anderson G, Goulet JP, et al.; International RDC/TMD Consortium Network, International association for Dental Research; Orofacial Pain Special Interest Group, International Association for the Study of Pain. Diagnostic criteria for temporomandibular disorders (DC/TMD) for clinical and research applications: recommendations of the international RDC/TMD consortium Network* and orofacial pain special interest group†. Journal of Oral & Facial Pain and Headache. 2014; 28: 6–27.

[6] Dworkin SF, LeResche L. Research diagnostic criteria for temporomandibular disorders: review, criteria, examinations and specifications, critique. Journal of Craniomandibular Practice. 1992; 6: 301–355.

[7] Taimeh D, Leeson R, Fedele S, Riordain RN. A meta-synthesis of the experience of chronic temporomandibular disorder patients within health care services. Journal of Oral & Facial Pain and Headache. 2023; 37: 55–73.

[8] Madhavi A, Sujatha MM, Mazhar M, Pabba K, Lavanya G, Gupta A. Evaluating the influence of acute and chronic orofacial pains on the overall comprehensive quality of life. Cureus. 2024; 16: e63625.

[9] Yap AU, Lai YC, Ho HCW. Prevalence of temporomandibular disorders and their associated factors in Confucian heritage cultures: a systematic review and meta-analysis. Journal of Oral Rehabilitation. 2024; 51: 2169–2194.

[10] Khan A, Liu S, Tao F. Mechanisms underlying sex differences in temporomandibular disorders and their comorbidity with migraine. Brain Sciences. 2024; 14: 707.

[11] Kapos FP, Craig KD, Anderson SR, Bernardes SF, Hirsh AT, Karos K, et al. Social determinants and consequences of pain: toward multilevel, intersectional, and life course perspectives. The Journal of Pain. 2024; 25: 104608.

[12] Svensson P, Sharav Y, Benoliel R. Myalgia, myofascial pain, tension-type headaches, and fibromyalgia. In Sharav Y, Benoliel R (eds.) Orofacial pain and headache (pp. 195–256). 2nd edn. Quintessence Publishing Co, Inc: Hanover Park, IL. 2015.

[13] Simons DG. Myofascial pain syndromes. Archives of Physical Medicine and Rehabilitation. 1984; 65: 561.

[14] Reeves JL, Jaeger B, Graff-Radford SB. Reliability of the pressure algometer as a measure of myofascial trigger point sensitivity. Pain. 1986; 24: 313–321.

[15] Zagury JG, Ananthan S, Quek SYP, Subramanian G. Myofascial temporomandibular disorders at a turning point: pragmatic or evidence-based management? Dental Clinics of North America. 2023; 67: 335–348.

[16] Matuska W, Matuska J, Skorupska E, Siwek M, Herrero P, Santafé MM. Can myofascial trigger points involve Nociplastic pain? A scoping review on animal models. Journal of Pain Research. 2023; 16: 3747–3758.

[17] Fernández-de-las-Penas C, Svensson P. Myofascial temporomandibular disorder. Current Rheumatology Reviews. 2016; 12: 40–54.

[18] Elbarbary M, Goldberg M, Tenenbaum HC, Lam DK, Freeman BV, Pustaka DJ, et al. Assessment of concordance between chairside ultrasonography and digital palpation in detecting myofascial trigger points in masticatory myofascial pain syndrome. Journal of Endodontics. 2023; 49: 129–136.

[19] Costa YM, Ariji Y, Ferreira DMAO, Bonjardim LR, Conti PCR, Ariji E, et al. Muscle hardness and masticatory myofascial pain: assessment and clinical relevance. Journal of Oral Rehabilitation. 2018; 45: 640–646.

[20] Schmidt RF. Fundamentals of sensory physiology. 3rd edn. Springer-Verlag: Berlin. 1986.

[21] Svensson P, Baad-Hansen L, Pigg M, List T, Eliav E, Ettlin D, et al.; Special Interest Group of Oro-facial Pain. Guidelines and recommendations for assessment of somatosensory function in oro-facial pain conditions—a taskforce report. Journal of Oral Rehabilitation. 2011; 38: 366–394.

[22] Costa YM, Bonjardim LR, Conti PCR, Svensson P. Psychophysical evaluation of somatosensory function in oro-facial pain: achievements and challenges. Journal of Oral Rehabilitation. 2021; 48: 1066–1076.

[23] Weaver KR, Griffioen MA, Klinedinst NJ, Galik E, Duarte AC, Colloca L, et al. Quantitative sensory testing across chronic pain conditions and use in special populations. Frontiers in Pain Research. 2022; 2: 779068.

[24] Headache classification committee of the international headache society (IHS) the international classification of headache disorders, 3rd edition. Cephalalgia. 2018; 38: 1–211.

[25] Hoeppli ME, Thurston TS, Roy M, Light AR, Amann M, Gracely RH, et al. Development of a computerized 2D rating scale for continuous and simultaneous evaluation of two dimensions of a sensory stimulus. Frontiers in Psychology. 2023; 14: 1127699.

[26] Ananthan S, Patil AG, Jaiswal D, Nasri-Heir C, Heir GM, Benoliel R. Sensory changes related to dental implant placement: a scoping review. Journal of Oral & Facial Pain and Headache. 2022; 36: 165–186.

[27] Langemark M, Olesen J. Pericranial tenderness in tension headache. A blind, controlled study. Cephalalgia. 1987; 7: 249–255.

[28] Suzuki K, Baad-Hansen L, Svensson P. Verbal instructions influence pain thresholds assessment: a study using manual and electronic mechanical stimulators. European Journal of Pain. 2017; 21: 900–906.

[29] Madsen BK, Søgaard K, Andersen LL, Skotte J, Tornøe B, Jensen RH. Neck/shoulder function in tension-type headache patients and the effect of strength training. Journal of Pain Research. 2018; 11: 445–454.

[30] Fernández-de-Las-Peñas C, Cuadrado ML, Arendt-Nielsen L, Ge HY, Pareja JA. Increased pericranial tenderness, decreased pressure pain threshold, and headache clinical parameters in chronic tension-type headache patients. The Clinical Journal of Pain. 2007; 23: 346–352.

[31] Aaseth K, Grande RB, Lundqvist C, Russell MB. Pericranial tenderness in chronic tension-type headache: the Akershus population-based study of chronic headache. The Journal of Headache and Pain. 2014; 15: 58.

[32] Zhang Y, Shao S, Zhang J, Wang L, Wang K, Svensson P. Temporal summation and motor function modulation during repeated jaw movements in patients with temporomandibular disorder pain and healthy controls. Pain. 2017; 158: 1272–1279.

[33] Sessle BJ, Hu JW, Amano N, Zhong G. Convergence of cutaneous, tooth pulp, visceral, neck and muscle afferents onto nociceptive and non-nociceptive neurones in trigeminal subnucleus caudalis (medullary dorsal horn) and its implications for referred pain. Pain. 1986; 27: 219–235.

[34] Sessle BJ. Fifty years of development of neuroscientific insights into oro-facial pain and its control. Journal of Oral Rehabilitation. 2023; 50: 860–876.

[35] Sessle BJ, Baad-Hansen L, Exposto F, Svensson P. Orofacial pain. In Lynch ME, Craig KD, Peng WHP (eds.) Clinical pain management: a practical guide (pp. 343–354). 2nd edn. Wiley Blackwell: Oxford, UK. 2022.

[36] Simons DG and Travell JG. Myofascial pain and dysfunction: the trigger point manual. 1st edn. Williams & Wilkins: Baltimore. 1983.

[37] Svensson P, Bak J, Troest T. Spread and referral of experimental pain in different jaw muscles. Journal of Oral & Facial Pain and Headache. 2003; 17: 214–223.

[38] Fernández-de-Las-Peñas C, Galán-Del-Río F, Alonso-Blanco C, Jiménez-García R, Arendt-Nielsen L, Svensson P. Referred pain from muscle trigger points in the masticatory and neck-shoulder musculature in women with temporomandibular disoders. The Journal of Pain. 2010; 11: 1295–1304.

[39] Duffin PS, Smith A, Hawkins JM. Nonodontogenic odontalgia referred from the temporal tendon: a case report. Journal of Endodontics. 2020; 46: 1530–1534.

[40] Lövgren A, Visscher CM, Lobbezoo F, Yekkalam N, Vallin S, Wänman A, et al. The association between myofascial orofacial pain with and without referral and widespread pain. Acta Odontologica Scandinavica. 2022; 80: 481–486.

[41] Nolet PS, Yu H, Côté P, Meyer AL, Kristman VL, Sutton D, et al. Reliability and validity of manual palpation for the assessment of patients with low back pain: a systematic and critical review. Chiropractic & Manual Therapies. 2021; 29: 33.

[42] Hsieh CY, Hong CZ, Adams AH, Platt KJ, Danielson CD, Hoehler FK, et al. Interexaminer reliability of the palpation of trigger points in the trunk and lower limb muscles. Archives of Physical Medicine and Rehabilitation. 2000; 81: 258–264.

[43] Shah JP, Phillips TM, Danoff JV, Gerber LH. An in vivo microanalytical technique for measuring the local biochemical milieu of human skeletal muscle. Journal of Applied Physiology. 2005; 99: 1977–1984.

[44] Shah JP, Danoff JV, Desai MJ, Parikh S, Nakamura LY, Phillips TM, et al. Biochemicals associated with pain and inflammation are elevated in sites near to and remote from active myofascial trigger points. Archives of Physical Medicine and Rehabilitation. 2008; 89: 16–23.

[45] Moraska AF, Hickner RC. Letter to the editor: pumping the brakes on the biochemical milieu of myofascial trigger points. Archives of Physical Medicine and Rehabilitation. 2024; 105: 177–178.

[46] Masuda M, Iida T, Exposto FG, Baad-Hansen L, Kawara M, Komiyama O, et al. Referred pain and sensations evoked by standardized palpation of the masseter muscle in healthy participants. Journal of Oral & Facial Pain and Headache. 2018; 32: 159–166.

[47] Rongo R, Ekberg E, Nilsson IM, Al-Khotani A, Alstergren P, Conti PCR, et al. Diagnostic criteria for temporomandibular disorders [DC/TMD] for children and adolescents: an international Delphi study-Part 1-Development of Axis I. Journal of Oral Rehabilitation. 2021; 48: 836–845.

[48] Nilsson IM, Ekberg E, Michelotti A, Al-Khotani A, Alstergren P, Conti PCR, et al.; International Network for Orofacial Pain and Related Disorders (INfORM). Diagnostic criteria for temporomandibular disorders-INfORM recommendations: comprehensive and short-form adaptations for children. Journal of Oral Rehabilitation. 2023; 50: 99–112.

[49] Alonso-Blanco C, Fernández-de-las-Peñas C, Fernández-Mayoralas DM, de-la-Llave-Rincón AI, Pareja JA, Svensson P. Prevalence and anatomical localization of muscle referred pain from active trigger points in head and neck musculature in adults and children with chronic tension-type headache. Pain Medications. 2011; 12: 1453–1463.

[50] Almoznino G, Zini A, Zakuto A, Zlutzky H, Bekker S, Shay B, et al. Muscle tenderness score in temporomandibular disorders patients: a case-control study. Journal of Oral Rehabilitation. 2019; 46: 209–218.

[51] Durham J, Ohrbach R, Baad-Hansen L, Davies S, De Laat A, Goncalves DG, et al.; INfORM. Constructing the brief diagnostic criteria for temporomandibular disorders (bDC/TMD) for field testing. Journal of Oral Rehabilitation. 2024; 51: 785–794.

[52] Ekberg E, Nilsson IM, Michelotti A, Al-Khotani A, Alstergren P, Rodrigues Conti PC, et al; International Network for Orofacial Pain and Related Disorders Methodology (INfORM). Diagnostic criteria for temporomandibular disorders-INfORM recommendations: comprehensive and short-form adaptations for adolescents. Journal of Oral Rehabilitation. 2023; 50: 1167–1180.

[53] Bendtsen L, Jensen R, Jensen NK, Olesen J. Muscle palpation with controlled finger pressure: new equipment for the study of tender myofascial tissues. Pain. 1994; 59: 235–239.

[54] Bendtsen L, Jensen R, Jensen NK, Olesen J. Pressure-controlled palpation: a new technique which increases the reliability of manual palpation. Cephalalgia. 1995; 15: 205–210.

[55] Bendtsen L, Jensen R, Olesen J. Qualitatively altered nociception in chronic myofascial pain. Pain. 1996; 65: 259–264.

[56] Schytz HW, Olesen J. Laboratory tests of headache disorders—dawn of a new era? Cephalalgia. 2016; 36: 1268–1290.

[57] Futarmal S, Kothari M, Ayesh E, Baad-Hansen L, Svensson P. New palpometer with implications for assessment of deep pain sensitivity. Journal of Dental Research. 2011; 90: 918–922.

[58] Kothari SF, Kothari M, Baad-Hansen L, Svensson P. Comparison of techniques for evaluation of deep pain sensitivity in the craniofacial region. Journal of Oral & Facial Pain and Headache. 2012; 26: 225–232.

[59] Kothari SF, Kothari M, Zambra RF, Baad-Hansen L, Svensson P. Standardization of muscle palpation- methodological considerations. The Clinical Journal of Pain. 2014; 30: 174–182.

[60] Pillai RS, Kothari SF, Svensson P, Castrillon E. Comparison of force profiles from two musculoskeletal palpation methods: a methodological study. Journal of Oral Rehabilitation. 2024; 51: 879–885.

[61] Iwata Y, Nishimori H, Iida T, Masuda M, Yoshida K, Ishii Y, et al. Effect of clinical experience and training with visual feedback on standardized palpation outcomes-potential implications for assessment of jaw muscle sensitivity. Journal of Oral Rehabilitation. 2024; 51: 601–610.

[62] Faghihian H, Böthun A, Häggman-Henrikson B, Lalouni M, Svensson P, Hellström F, et al. Gender variability in palpation performance for temporomandibular disorders with three different methods: an experimental study. European Journal of Oral Sciences. 2024; 132: e13026.

[63] Rolke R, Baron R, Maier C, Tölle TR, Treede -DR, Beyer A, et al. Quantitative sensory testing in the German Research Network on Neuropathic Pain (DFNS): standardized protocol and reference values. Pain. 2006; 123: 231–243.

[64] Svensson P, Graven-Nielsen T, Arendt-Nielsen L. Mechanical hyperesthesia of human facial skin induced by tonic painful stimulation of jaw muscles. Pain. 1998; 74: 93–100.

[65] Exposto FG, Udagawa G, Naganawa T, Svensson P. Comparison of masseter muscle referred sensations after mechanical and glutamate stimulation: a randomized, double-blind, controlled, cross-over study. Pain. 2018; 159: 2649–2657.

[66] Serrano-Hernanz G, Futarmal Kothari S, Castrillón E, Álvarez-Méndez AM, Ardizone-García I, Svensson P. Importance of standardized palpation of the human temporomandibular joint. Journal of Oral & Facial Pain and Headache. 2019; 33: 220–226.

[67] Yang S, Exposto FG, Mahmoodi S, Svensson P. Mechanical sensitivity changes in pericranial muscles after local anesthesia and experimentally induced pain in the temporalis tendon: implications for headache and facial pain. Cephalalgia. 2022; 42: 1127–1137.

[68] Renner N, Costa YM, Castrillon EE, Exposto FG. Reliability of an intraoral extension for intraoral palpation and assessment of mechanical sensitivity of the temporal tendon. Journal of Oral Rehabilitation. 2024; 51: 1848–1861.

[69] Naganawa T, Iida T, Baad-Hansen L, Ando T, Svensson P. Application of a new palpometer for intraoral mechanical pain sensitivity assessment. Journal of Oral & Facial Pain and Headache. 2013; 27: 336–342.

[70] Masuda M, Hayakawa H, Boudreau SA, Iida T, Svensson P, Komiyama O. Standardized palpation of the temporalis muscle evoke referred pain and sensations in individuals without TMD. Clinical Oral Investigations. 2022; 26: 1241–1249.

[71] Hayakawa H, Iida T, Honda-Sakaki M, Masuda M, Svensson P, Komiyama O. Drop homotopic effects of masseter-muscle pain on somatosensory sensitivity in healthy participants. Scientific Reports. 2021; 11: 10575.

[72] Svensson P, Exposto F. Patients with temporomandibular disorders. In Melsen Birte, Luzi Cesare (eds.) Adult orthodontics (pp. 362–378). 2nd edn. Wiley Blackwell: Oxford, UK. 2022.

[73] Svensson P, List T, Hector G. Analysis of stimulus-evoked pain in patients with myofascial temporomandibular pain disorders. Pain. 2001; 92: 399–409.

[74] Exposto FG, Huang M, Haasnoot T, Koutris M, Lobbezoo F, Bendixen KH, et al. Location of mechanically-evoked referred sensations within the trigeminal region are not altered following a heterotopic painful stimulus. Scientific Reports. 2022; 12: 21181.

[75] Schmidt-Hansen PT, Svensson P, Jensen TS, Graven-Nielsen T, Bach FW. Patterns of experimentally induced pain in pericranial muscles. Cephalalgia. 2006; 26: 568–577.

[76] Svensson P, Michelotti A, Lobbezoo F, List T. The many faces of persistent orofacial muscle pain. Journal of Oral & Facial Pain and Headache. 2015; 29: 207–208.

[77] Exposto FG, Masuda M, Castrillon EE, Svensson P. Effects of nerve growth factor experimentally-induced craniofacial muscle sensitization on referred pain frequency and number of headache days: a double-blind, randomized placebo-controlled study. Cephalalgia. 2018; 38: 2006–2016.

[78] Costa YM, Exposto FG, Castrillon EE, Conti PCR, Bonjardim LR, Svensson P. Local anaesthesia decreases nerve growth factor induced masseter hyperalgesia. Scientific Reports. 2020; 10: 15458.

[79] Salis B, Svensson P, Exposto FG. Referred sensation location can be altered by a strong heterotopic nociceptive stimulus: implications for clinical pain conditions. Pain. 2023; 164: e242–e250.

[80] Sago T, Costa YM, Ferreira DM, Svensson P, Exposto FG. Referred sensations in the orofacial region are associated with a decreased descending pain inhibition and modulated by remote noxious stimuli and local anesthesia. Pain. 2023; 164: 2228–2238.

[81] Ohrbach R, Gale EN. Pressure pain thresholds in normal muscles: reliability, measurement effects, and topographic differences. Pain. 1989; 37: 257–263.

[82] Ohrbach R, Gale EN. Pressure pain thresholds, clinical assessment, and differential diagnosis: reliability and validity in patients with myogenic pain. Pain. 1989; 39: 157–169.

[83] List T, Helkimo M, Karlsson R. Influence of pressure rates on the reliability of a pressure threshold meter. Journal of Craniomandibular Disorders. 1991; 5: 173–178.

[84] McMillan AS, Lawson ET. Effect of tooth clenching and jaw opening on pain-pressure thresholds in the human jaw muscles. Journal of Oral & Facial Pain and Headache. 1994; 8: 250–257.

[85] Svensson P, Arendt-Nielsen L, Nielsen H, Larsen JK. Effect of chronic and experimental jaw muscle pain on pain-pressure thresholds and stimulus-response curves. Journal of Oral & Facial Pain and Headache. 1995; 9: 347–356.

[86] Bernhardt O, Schiffman EL, Look JO. Reliability and validity of a new fingertip-shaped pressure algometer for assessing pressure pain thresholds in the temporomandibular joint and masticatory muscles. Journal of Oral & Facial Pain and Headache. 2007; 21: 29–38.

[87] Reid KI, Carlson C, Rayens MK, Gracely RH. The influence of cutaneous tissue afferents on masticatory pain-pressure thresholds. Journal of Oral & Facial Pain and Headache. 1996; 10: 324–329.

[88] Takahashi K, Taguchi T, Itoh K, Okada K, Kawakita K, Mizumura K. Influence of surface anesthesia on the pressure pain threshold measured with different-sized probes. Somatosensory & Motor Research. 2005; 22: 299–305.

[89] Graven-Nielsen T, Mense S, Arendt-Nielsen L. Painful and non-painful pressure sensations from human skeletal muscle. Experimental Brain Research. 2004; 159: 273–283.

[90] Pedulla R, Glugosh J, Jeyaseelan N, Prevost B, Velez E, Winnitoy B, et al. Associations of gender role and pain in musculoskeletal disorders: a mixed-methods systematic review. The Journal of Pain. 2024; 25: 104644.

[91] Lövgren A, Häggman-Henrikson B, Fjellman-Wiklund A, Begic A, Landgren H, Lundén V, et al. The impact of gender of the examiner on orofacial pain perception and pain reporting among healthy volunteers. Clinical Oral Investigations. 2022; 26: 3033–3040.

[92] McMillan AS. Pain-pressure threshold in human gingivae. Journal of Oral & Facial Pain and Headache. 1995; 9: 44–50.

[93] Liu R, Gu X, Zhang J, Yu L, Chen W, Wang K, et al. Test-retest reliability of a new technique with pressure algometry applied to teeth in healthy Chinese individuals. European Journal of Oral Sciences. 2016; 124: 259–265.

[94] Smeets Y, Soer R, Chatziantoniou E, Preuper RHRS, Reneman MF, Wolff AP, et al. Role of non-invasive objective markers for the rehabilitative diagnosis of central sensitization in patients with fibromyalgia: a systematic review. Journal of Back and Musculoskeletal Rehabilitation. 2024; 37: 525–584.

[95] Fernández-de-las-Peñas C, Galán-del-Río F, Fernández-Carnero J, Pesquera J, Arendt-Nielsen L, Svensson P. Bilateral widespread mechanical pain sensitivity in women with myofascial temporomandibular disorder: evidence of impairment in central nociceptive processing. The Journal of Pain. 2009; 10: 1170–1178.

[96] Kothari SF, Baad-Hansen L, Oono Y, Svensson P. Somatosensory assessment and conditioned pain modulation in temporomandibular disorders pain patients. Pain. 2015; 156: 2545–2555.

[97] Menéndez-Torre Á, Martin-Pintado-Zugasti A, Paris-Alemany A, Bocos-Corredor E, Molina-Álvarez M, Arribas-Romano A, et al. Pain sensitization and pain-related psychological factors in patients with temporomandibular disorders: an observational cross-sectional study. Clinical Oral Investigations. 2024; 28: 594.

[98] Castien RF, van der Wouden JC, De Hertogh W. Pressure pain thresholds over the cranio-cervical region in headache: a systematic review and meta-analysis. The Journal of Headache and Pain. 2018; 19: 9.

[99] Cayrol T, Meeus M, Aron V, Gatto C, Mouraux A, Roussel NA, et al. Evidence for alterations to dynamic quantitative sensory tests in patients with chronic temporomandibular myalgia: a systematic review of observational studies with meta-analysis. Journal of Oral Rehabilitation. 2022; 49: 654–670.

[100] Santos Silva R S, Conti PC, Lauris JR, da Silva RO, Pegoraro LF. Pressure pain threshold in the detection of masticatory myofascial pain: an algometer-based study. Journal of Oral & Facial Pain and Headache. 2005; 19: 318–24.

[101] Cunha CO, Pinto-Fiamengui LM, Castro AC, Lauris JR, Conti PC. Determination of a pressure pain threshold cut-off value for the diagnosis of temporomandibular joint arthralgia. Journal of Oral Rehabilitation. 2014; 41: 323–329.

[102] Finocchietti S, Graven-Nielsen T, Arendt-Nielsen L. Dynamic mechanical assessment of muscle hyperalgesia in humans: the dynamic algometer. Pain Research and Management. 2015; 20: 29–34.

[103] Palacios-Cena M, Gomez-Mayordomo V, Garcia-Azorin D, Gonzalez-Garcia N, Cuadrado ML, Fernandez-de-Las-Penas C, et al. Dynamic pressure pain hypersensitivity as assessed by roller pressure algometry in episodic cluster headache. Pain Physician Journal. 2020; 23: 219–227.

[104] Álvarez-Méndez AM, Exposto FG, Castrillon EE, Svensson P. Systematic mapping of pressure pain thresholds of the masseter and temporalis muscles and assessment of their diversity through the novel application of entropy. Journal of Oral & Facial Pain and Headache. 2017; 31: 362–371.

[105] Castrillon EE, Exposto FG, Sato H, Tanosoto T, Arima T, Baad-Hansen L, et al. Entropy of masseter muscle pain sensitivity: a new technique for pain assessment. Journal of Oral & Facial Pain and Headache. 2017; 31: 87–94.

[106] Tang Z, Chen Y, Zhou W, Zhang J, Wang R, Wang K, et al. Reliability of mechanical sensitivity mapping in the orofacial region of healthy chinese individuals: towards standardized assessment of somatosensory function. Journal of Oral & Facial Pain and Headache. 2018; 32: 400–408.

[107] Aisaiti A, Zhou Y, Wen Y, Zhou W, Wang C, Zhao J, et al. Effect of photobiomodulation therapy on painful temporomandibular disorders. Scientific Reports. 2021; 11: 9049.

[108] Tanguay-Sabourin C, Fillingim M, Guglietti GV, Zare A, Parisien M, Norman J, et al. A prognostic risk score for development and spread of chronic pain. Nature Medicine. 2023; 29: 1821–1831.

[109] Kielstra SC, Reezigt RR, Coppieters MW, de Vries R, Arendt-Nielsen L, Petersen KK, et al. A myriad of methods to determine temporal summation of pain in people with musculoskeletal pain and healthy participants: a scoping review. PAIN Reports. 2024; 9: e1176.

[110] Santiago V, Janal MN, Cook DB, Raphael KG. Temporal summation and aftersensations of second pain in women with myofascial temporomandibular disorder differ by presence of temporomandibular joint pain. Journal of Pain Research. 2022; 15: 3275–3286.

[111] Santiago V, Janal MN, Cook DB, Raphael KG. Examination of conditioned pain modulation in myofascial TMD with consideration of temporal summation. The Journal of Pain. 2024; 25: 104430.

[112] Takizawa K, Ozasa K, Yan Z, Hitomi S, Fujita-Yoshigaki J, Okubo M, et al. Association between central sensitivity syndrome and psychophysical factors in patients with masticatory myofascial pain. Journal of Oral Science. 2024; 66: 176–181.

[113] Cayrol T, van den Broeke EN, Gerard E, Meeus M, Mouraux A, Roussel N, et al. Chronic temporomandibular disorders are associated with higher propensity to develop central sensitization: a case-control study. Pain. 2023; 164: e251–e258.

[114] Brazenor GA, Malham GM, Teddy PJ. Can central sensitization after injury persist as an autonomous pain generator? A comprehensive search for evidence. Pain Medicine. 2022; 23: 1283–1298.

[115] Le Bars D, Dickenson AH, Besson JM. Diffuse noxious inhibitory controls (DNIC). I. Effects on dorsal horn convergent neurones in the rat. Pain. 1979; 6: 283–304.

[116] Ramaswamy S, Wodehouse T. Conditioned pain modulation-a comprehensive review. Neurophysiologie Clinique. 2021; 51: 197–208.

[117] Yarnitsky D, Bouhassira D, Drewes AM, Fillingim RB, Granot M, Hansson P, et al. Recommendations on practice of conditioned pain modulation (CPM) testing. European Journal of Pain. 2015; 19: 805–806.

[118] Billens A, Van Oosterwijck S, Dhondt E, Meeus M, De Greef I, Van Damme S, et al. The influence of expectations and attention on conditioned pain modulation: a systematic review and meta-analysis. Clinical Psychology Review. 2024; 114: 102517.

[119] Oono Y, Wang K, Svensson P, Arendt-Nielsen L. Conditioned pain modulation evoked by different intensities of mechanical stimuli applied to the craniofacial region in healthy men and women. Journal of Oral & Facial Pain and Headache. 2011; 25: 364–375.

[120] Yarnitsky D. Role of endogenous pain modulation in chronic pain mechanisms and treatment. Pain. 2015; 156: S24-S31.

[121] Yarnitsky D, Granot M, Nahman-Averbuch H, Khamaisi M, Granovsky Y. Conditioned pain modulation predicts duloxetine efficacy in painful diabetic neuropathy. Pain. 2012; 153: 1193–1198.

[122] Bruehl S, France CR, Stone AL, Gupta R, Buvanendran A, Chont M, et al. Greater conditioned pain modulation is associated with enhanced morphine analgesia in healthy individuals and patients with chronic low back pain. The Clinical Journal of Pain. 2021; 37: 20–27.

[123] Ferreira DMAO, Soares FFC, Raimundini AA, Bonjardim LR, Costa YM, Conti PCR. Prediction of duloxetine efficacy in addition to self-management in painful temporomandibular disorders: a randomised, placebo-controlled clinical trial. Journal of Oral Rehabilitation. 2024; 51: 476–486.

[124] Lawn T, Sendel M, Baron R, Vollert J. Beyond biopsychosocial: the keystone mechanism theory of pain. Brain, Behavior, and Immunity. 2023; 114: 187–192.

[125] Larsen DB, Uth XJ, Arendt-Nielsen L, Petersen KK. Modulation of offset analgesia in patients with chronic pain and healthy subjects—a systematic review and meta-analysis. Scandinavian Journal of Pain. 2021; 22: 14–25.

[126] Moana-Filho EJ, Herrero Babiloni A, Nisley A. Endogenous pain modulation assessed with offset analgesia is not impaired in chronic temporomandibular disorder pain patients. Journal of Oral Rehabilitation. 2019; 46: 1009–1022.

[127] Chen TC, Lin CS. Neuroimaging meta-analysis of brain mechanisms of the association between orofacial pain and mastication. Journal of Oral Rehabilitation. 2023; 50: 1070–1081.

[128] Shrivastava M, Ye L. Neuroimaging and artificial intelligence for assessment of chronic painful temporomandibular disorders-a comprehensive review. International Journal of Oral Science. 2023; 15: 58.

[129] Gracely RH, Petzke F, Wolf JM, Clauw DJ. Functional magnetic resonance imaging evidence of augmented pain processing in fibromyalgia. Arthritis & Rheumatology. 2002; 46: 1333–1343.

[130] Sandström A, Ellerbrock I, Löfgren M, Altawil R, Bileviciute-Ljungar I, Lampa J, et al. Distinct aberrations in cerebral pain processing differentiating patients with fibromyalgia from patients with rheumatoid arthritis. Pain. 2022; 163: 538–547.

[131] Greenspan JD, Slade GD, Bair E, Dubner R, Fillingim RB, Ohrbach R, et al. Pain sensitivity and autonomic factors associated with development of TMD: the OPPERA prospective cohort study. The Journal of Pain. 2013; 14: T63–T74.e1–6.

[132] Slade GD, Sanders AE, Ohrbach R, Fillingim RB, Dubner R, Gracely RH, et al. Pressure pain thresholds fluctuate with, but do not usefully predict, the clinical course of painful temporomandibular disorder. Pain. 2014; 155: 2134–2143.

[133] Bair E, Gaynor S, Slade GD, Ohrbach R, Fillingim RB, Greenspan JD, et al. Identification of clusters of individuals relevant to temporomandibular disorders and other chronic pain conditions: the OPPERA study. Pain. 2016; 157: 1266–1278.

[134] Gaynor SM, Bortsov A, Bair E, Fillingim RB, Greenspan JD, Ohrbach R, et al. Phenotypic profile clustering pragmatically identifies diagnostically and mechanistically informative subgroups of chronic pain patients. Pain. 2021; 162: 1528–1538.

[135] Andersen S, Petersen MW, Svendsen AS, Gazerani P. Pressure pain thresholds assessed over temporalis, masseter, and frontalis muscles in healthy individuals, patients with tension-type headache, and those with migraine—a systematic review. Pain. 2015; 156: 1409–1423.