Grinding and clenching of teeth is medically called bruxism. Stress was thought to be the reason behind it but latest researches have confirmed its relation with sleep apnea. Brain cycles through lighter and deeper stages of sleep during night. All the muscles in the body fully relax during the deep cycle. This troubles the airway and causes heaviness in jaw and blockage of the airway by the tongue. Scans taken at this stage shows that the grinding of teeth reopened the airway and person can breathe again. It is the physiological response caused by the hypercapnia (increased CO2 in the body). Thus grinding is one of the symptoms of OSA that can save person’s life. But conversely, causes morning headaches and TMD in the long run.