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Myofascial pain is the second most recurrent type of orofacial pain and is estimated that 33% of people have symptoms in the face and mastication muscles.⁵ Orofacial pain can be associated with numerous pathological conditions or disorders related to somatic and neurological structures, and have confounding biopsychosocial components.⁴

Central nervous system differences in the trigeminal nucleus and limbic structures have been demonstrated in people with myofascial pain, and chronic pain results in sympathetic nervous system overactivation. ³ The incidence of altered sensation after dental or mandibular surgery varies, ranging from 1% to 5% for third molar removal, up to 80% to 85% for sagittal split osteotomies. ⁶

There is a neurophysiological relationship between the upper cervical spine, TMD, tooth pain, and even headaches. ¹ The trigeminal nerve is divided in to three branches. The ophthalmic nerve is responsible for sensory innervation of the face and skull above the palpebral fissure and the eye and portions of the nasal cavity.⁷ The mandibular nerve provides motor innervation to the muscles of mastication and sensory innervation to the TMJ, teeth, and jaw, via the auriculotemporal branch. ¹ The maxillary nerve is a sensory branch and innervates portions of the nasal cavity, sinuses, maxillary teeth, palate, and the middle portion of the face and skull above the mouth and below the forehead.⁷ The spinal tract of the trigeminal nerve synapses with the dorsal horn of C1 – C3, thus, helping explain pain referral between the craniofacial area and upper cervical spine.⁸

The dense interconnections between the trigeminal as well as facial, glossopharyngeal and vagus nerves, can give rise to local and referred pain and associated symptomatology.⁸ Muscles of mastication may refer to the teeth.³ The anterior digastric muscle can cause toothache via referred pain to the central and lateral mandibular incisors.⁸ The masseter muscle can refer pain to the ipsilateral mandibular and maxillary three molars.⁸ The temporalis can refer pain to any of the ipsilateral maxillary teeth. ⁸ Odontogenic pain can mimic maxillary sinusitis-like symptoms in temporomandibular disorders or neuropathic pain. ⁴ One hypothesis for dental pain is the osmolality theory, whereby the dentine fluids can elicit an action potential within the A delta and C fibers in the pulp when stimulated by mechanical stimulation. ⁴

Dry needling can stimulate an analgesic response, by stimulating the tissues in the surrounding areas,   similar to the analgesic effects of commonly used pain medication, such as ibuprofen or paracetamol. ²,⁴ A systematic review and meta-analysis suggested dry needling increased pain pressure threshold compared with sham therapy, and decreased pain intensity compared to lidocaine injection and combination drug therapy (methocarbamol and paracetamol). ⁵ Dry needling can mitigate central sensitization by segmental inhibition or gate control, release of endogenous opioids, and activation of serotonergic and noradrenergic descending inhibitory tracts.⁸

A recent multi-center randomized control trial found dry needling and upper cervical spinal manipulation to be more effective than interocclusal splint therapy, diclofenac, and TMJ mobilization in patients with TMD.¹ The semi standardized TMJ protocol used in the RCT targeted the inferior head of the lateral pterygoid muscle, the superficial masseter muscle, the anterosuperior and anteroinferior aspects of the temporalis muscle, and the periarticular capsule of the posterior TMJ. A retrospective study using many of the similar points as the RCT  and found decreased pain with improved mouth opening in TMD, compared to occlusal splints and low level laser therapy. ⁹

The evaluation process for patients presenting with orofacial or TMD pain to physical therapy should include a complete cranial nerve screen, with particular attention to the trigeminal nerve, as well as screening of the upper cervical vertebrae. ³ The  complex  interplay between the sympathetic and trigeminal nervous  systems  and  an  increased  understanding of the centralization of pain have resulted in an important role not only for dentists, physical therapists, but also behavioral scientists, for successful  management  of  chronic pain related to TMD. ³