My Mom (90) with dementia and very little mobility sleeps most of the time but at night moans and groans very loud. Advice?

Vinatha, if your Mom is sleeping on a flat pillow maybe she is experiencing acid reflex [it's acid from the stomach that is coming back up into one's throat and it can feel like your throat is on fire]. Experiment with using a fluff pillow which helps raise her head, or if she is already using one pillow, then try two. Check with her primary doctor first to be sure it won't cause any other issues by using more than one pillow.

Do the moans sound like she is in pain? Or does it sound more like spontaneous utterances? My father used to quote scripture loudly in the middle of the night. I'm not sure why and I'm not sure he was fully awake when he was doing it. I would hear it coming from their room. Then things would go quiet again. It must be that what was in his mind spilled out while he was sleeping.

Stilnot (ambien) is meant for short term insomnia. I assume you are trying to help her sleep at night rather than during the day? Moaning usually accompanies pain or perhaps mental distress. Is she on any meds for pain or anxiety? I find that melatonin at bedtime works very well for us without the need of more powerful drugs. Try to engage her more during the day, read to her, play music, talk. Is she able to get up at all? Being more active during the day the better will help her sleep better at night.