Grinding of the teeth at night is a common problem but as you have mentioned that it is so severe that even your son can hear it , it is problematic. Grinding of teeth is basically related to stress and tension. The first solution is not just taking a diazepam, first you should make some modifications in your lifestyle. Take less tension as you will spoil your health and then be alert of your grinding because if you are doing it at night you must be doing at day time at the time of stress, anger or tension. Notice it and try to avoid it. Also get the treatment of tooth infection done. Then use nightguard and some muscle relaxant. If still not relieved then consult your physician for another medication But I think you will get relieved by these things