Psychoneuroimmunology and its relationship to the differential diagnosis of temporomandibular disorders.

Psychoneuroimmunology (PNI) is a field of medicine which joins immunology and neurobiology. It focuses on the relationship of stress upon the hypothalamic-adrenal-pituitary (HPA) axis. Depletion of hormones and neurotransmitters within the HPA-axis, as a result of stress, can lead to a multitude of diseases and disorders. Therefore, it is necessary for the dentist to be familiar with PNI and the HPA-axis in order to make an accurate diagnosis of TMD.