Orofacial Pain and Sleep

Pain is defined by the International Association for the Study of Pain (IASP) as ‘‘.an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.’’ Acute pain is short term and although the impact on sleep may be significant, it does not have a longstanding influence. Chronic pain, however, can have a long-standing and negative impact on sleep. The IASP defines chronic pain as ‘‘pain without apparent biologic function that has persisted beyond the normal tissue healing time’’ (usually taken to be 3 months). Chronic pain includes such disorders as arthritis, neuropathic pain, and sometimes headache. Melzack in 1993 described a pain neuromatrix that involved all regions of the brain, helping to explain the emotional and cognitive response to the pain. Nofzinger and Derbyshire described the ‘‘significant overlaps between the neuromatrix of pain and that of sleep.’’ The interrelationship between pain and sleep is complex and that relationship may be overlooked by clinicians treating only orofacial pain or only treating sleep disorders. Pain and sleep seem to represent opposing forces. Pain is a conscious process and in going to sleep, awareness of the surrounding environment decreases and the neural networks related to wakefulness become less active. Nevertheless, pain can intrude into the unconsciousness of sleep, bringing pain into consciousness, thereby disturbing sleep. Melzack and Wall in 1965 proposed a pain modulating system called the ‘‘gate control theory of pain.’’ This system has been modified over the years as the understanding of ascending and descending modulation has increased. Nevertheless,