Autonomic mechanisms in oral sensations.

Sympathetic fibres reach the oro-facial region by several routes, the main one being via the carotid nerve and the trigeminal or facial nerves. Sensory receptors in this region may be affected non-specifically by activity in these fibres as a result of, for example, changes in local blood flow or contraction of pilo-erector muscles. There is evidence that the responses of intradental receptors and periodontal mechanoreceptors may change during stimulation of the cervical sympathetic trunk, but these effects are probably not due to specific modulatory mechanisms. There is no evidence that the parasympathetic nervous system affects the properties of oral receptors. Patients with Horner's syndrome appear to have no sensory abnormalities, apart from pain which is sometimes associated with the onset of the condition. Reflex sympathetic dystrophy seems to be rare in the oro-facial region.