[Mechanisms by which acute orofacial pain becomes chronic]

Pain is a complex, multidimensional experience encompassing sensory-discriminative, cognitive, emotional and motivational dimensions. These dimensions in the orofacial region have particular expression since the face and mouth have special biological, emotional and psychological meaning to each individual. Orofacial pain is frequent. Epidemiological studies reveal a high prevalence of severe pain in syndromes such as temporomandibular disorders (TMD), burning mouth syndrome and toothaches, as well as an important role of psychosocial influences, contributing to the persistence of these syndromes. Many of the difficulties experienced by clinicians with the diagnosis and management of acute and chronic orofacial pain stem from a lack of recognition and understanding of these complex conditions, the various intricate bio-psycho-social interactions and the neurobiology behind the chronicisation of acute pain. This text strives to review the important advances and insights into the peripheral processes by which noxious stimuli activates or modulates nociceptive afferent input into the brainstem, the neural pathways in the brainstem and higher levels of the trigeminal (V) somatosensory system and the mechanisms involved in the plasticity of nociceptive transmission. We shall link this knowledge to clinical correlates and suggest a therapeutic approach in acute orofacial pain, in the attempt to avoid the development of chronic pain.