why do children grind teeth in sleep   

Teeth grinding is usually not a major cause of concern. Teeth grinding occurs due to anxiety or stress. Try talking to your child when (s)he is awake. Try to understand what is bothering them and get to a solution together. Assure them that they can talk to you about any and everything. This should solve your child's teeth grinding problem. You can also consult a child psychologist to identify the reasons for stress or anxiety and cure it with counselling sessions. In some cases, teeth grinding may lead to some oral problems. For this, you can consult your child's dentist and get a mouth guard if the problem occurs frequently.