Two and a half year old baby sleep grinding teeth for more reasons, as follows: 1, cerebral cortex excitement: If the baby frolics and games during the day, causing abnormal excitement in the cerebral cortex, the upper and lower teeth will also move frequently after falling asleep. 2, mental tension: If the baby is frightened during the day causing mental tension, it will also produce the phenomenon of night grinding teeth. 3, frequent movement of the temporomandibular joint: There are early contact points in the upper and lower teeth, forming a bite When trauma or lead to (dental) interference, can induce frequent movement of the temporomandibular joint, so that the phenomenon of grinding teeth in bed. 4, parasites in the body: this will stimulate abnormal activity of the gastrointestinal tract, the emergence of night grinding teeth. 5, sleep with a bottle: the upper and lower teeth constantly rub during sleep, simulating the action of gnawing on a rubber nipple.