I have done it a few times with the obturator out (usually only because I forgot to do my exercises and already had taken it out for the night), but mostly use the therabite with it in. I think it gives an additional pressure point to help avoid too much on the front teeth.

Sharon, 57; Hard Palate; T1, High Grade, DX 6-12-09, Surgery, maxillectomy 7-14-09, 33 RT (9-2-09 to 10-19-09); Prothesis (obturator). None smoker, non drinker.