My daughter is now 4.5 and she starting grinding her teeth since she was a baby (she didn't get her first tooth until she was 10 months old). Her grinding got worse as time went by. Both her pediatrician and dentist said there was nothing we can really do about it and that it was caused by stress. Anyway, to make a long story short, we took her off of dairy and wheat and her grinding stopped (we went to a naturopath and we found out she had a "food sensitivity" to wheat and dairy). So it seems that teeth grinding can be caused by not only mental stress, but physical stress (teething, indigestion...).
