H.L.
Kathleen,
I spoke with my pediatrician and dentist. This is common for children around 4-5 because their adult teeth are getting ready. The kids grind their teeth only at night because it makes them feel better. The name of it is called Bruxism. Massaging the cheeks is one of the things that will relieve the clenching and grinding. My 5 yr old son does the same thing.