Teeth bite does not hurt, lying down when the pain may be caused by pulpitis, specific as follows. 1. When pulpitis occurs in the teeth, the tissue in the pulp is edematous, and the pressure in the pulp cavity may increase due to tissue necrosis and liquefaction, and the change of body position when lying down may accelerate the local blood circulation, leading to the intensification of the pressure in the pulp cavity and the tissue edema, and causing tooth pain. In addition, when lying down, mostly at night, night pain is a characteristic symptom of acute pulpitis. 2. When pulpitis occurs, there is usually no biting pain because the inflammation has not spread to the periapical tissues. There may be other reasons for the pain when lying down, so it is recommended to go to the hospital in time to clarify the cause of the disease and then carry out targeted treatment.