Hi Hazelnut,
Do you take an SSRI anti-depressant daily (Prozac, Zoloft, etc.) Recent reports have shown that these types of anti-d's may cause night-time clenching. If you are, either see about changing to a different type of anti-d or add a very small dose (7.5 mg or less) of Buspar to your daily meds. It does have to be prescribed by a doctor but it is very inexpensive.
Also if you aren't already, add Magnesium to your daily vitamins. Not only do I take the Mag that comes with Calcium but also 500 mg. of just Magnesium just before bed. Start at a lower dose and build up to allow your body to get used to it. It can cause diarrhea.
I personally cannot sleep on my back. I purchased a special pillow for side-sleepers and it does the trick for me.
God bless...
Carol