Many children grind their teeth at some stage. Your child might just clench his jaw quite firmly or he might grind so hard that it makes a noise.
Your child will not usually be woken up by the sound of his own teeth grinding but other people in the room might be!
In only a few very extreme cases, where the grinding is very regular, is it likely that your child could damage his teeth. Devices to protect teeth can help, and are available from dentists.
In most cases, there is no damage at all. If you are concerned, talk to a professional.
American Academy of Pediatric Dentistry, Council on Clinical Affairs. (2003). Policy on Oral Habits. Retrieved on 24 November 2005 from http://www.aapd.org/media/Policies_Guidelines/P_OralHabits.pdf.
Archhold, K.H., Pituch, K.J., Panabi, P., & Chervin, R.D. (2002). Symptoms of sleep disturbance among children at two general pediatric clinics. Journal of Pediatrics, 140, 97-102.
Giglio, P., Undevia, N., & Spire, J-P. (2005). The primary parasomnias: A review for neurologists. The Neurologist, 11, 90-97.