The history of a patient who suffered encephalopathy and coma is presented. A 25-year-old female consumed large quantities of cold water over several weeks, to control long-term dental pain. This eventually led to dilution hyponatraemia, followed by a seizure and encephalopathy. The patient made a good recovery after spending three days in neurological intensive care. Conventional endodontic therapy immediately resolved her symptoms following recovery from this life-threatening episode. Prior to her admission the patient had experienced difficulties in gaining access to effective emergency dental care. Her problems could have been avoided if appropriate management had been provided sooner. The dental profession should be aware of the potential life-threatening risk when continued water consumption is used to control the long-term pulpitic pain. Primary care agencies should ensure that information on local emergency dental services is well disseminated to the population. Dental surgeons should be able to manage acute dental pain.