Abstract
The term orofacial pain encompasses a diverse group of disorders affecting the highly innervated oral, facial, jaw and associated tissues and constitutes one of the most frequent and disabling dental and medical complaints. It also has a different neurobiological basis from that of pain in other parts of the body due to its unique anatomical and functional organisation of the trigeminal system. The present review aims to map out the continuum of acute nociception to persistent chronic pain. It starts with peripheral transduction of the noxious stimulation by trigeminal nociceptors and the machineries that transduce the noxious stimulation into electrical signals, such as transient receptor potential channels. These signals are then transmitted to the trigeminal brainstem sensory nuclear complex, with particular focus on the subnucleus caudalis, and the phenomenon of afferent convergence that is responsible for referred pain. The review highlights peripheral and central sensitization as the key amplifying mechanisms, neuroimmune and glial mechanisms sustaining these mechanisms and descending pathways that modulate nociceptive traffic. Special focus is on the transition from acute to chronic pain (chronification), maladaptive neuroplasticity, structural reorganization, and role of genetic, psychological and affective factors. A key contribution of this review is the integration of peripheral, central, neuroimmune, epigenetic and psychosocial mechanisms into a single mechanism-based framework of orofacial pain chronification specific to the trigeminal system, an integration that has not previously been assembled in this form. It is important to have a mechanism-based understanding of these processes in order to make an appropriate diagnosis, and for the development of individualized management of orofacial pain.
Keywords: Central Sensitization, Chronic Pain, Nociception, Neuroplasticity, Orofacial Pain, Trigeminal System.