Infant’s teeth clenching may be caused by imperfect development of temporomandibular joints, incomplete growth of teeth, lack of calcium, epilepsy, or psychological and emotional problems, and it is recommended to go to the hospital for examination and treatment. Temporomandibular joints are constantly developing during an infant’s growth and development, and during the period of underdevelopment, the joints may wobble, or appear to shake, when the infant clenches his or her teeth vigorously. When the back teeth are not fully erupted, infants may often clench their teeth by testing or rubbing against neighboring teeth on the opposite jaw. The child’s teeth clenching to make the jiggling appear due to faster growth and development and insufficient calcium absorption. Epileptics will clench their teeth and twitch involuntarily during a seizure. It may also occur when the baby is emotionally excited and when he or she is psychologically stressed.