Bell's palsy is an isolated facial paralysis of sudden onset caused by a neuritis of the seventh nerve within the facial canal. It occurs often in the adult man with a history of recent exposure to local cold, such as sleeping next to an open window, or in some cases it occurs after infections of the nasopharynx or masticator spaces. Especially, this neuropathy have linked with the major collagen disorders (diabetes mellitus). A segmental demyelination develops rapidly, with vascultitis in microinfarcts and ischemia to the nerve segment. The authors experienced about the bizarre neurological symptom of Bell's palsy after inferior alveolar nerve block anesthesia and TMJ dislocation in diabetic mellitus. The early and correct consultation with the multiple medical and dental departments was important to prevent the inadequate care & medicolegal problems.