How can we help my father if he is combative with anything my brother and I try to do to help?

My mother has dementia and we had to hospitalize her because she became agitated and combative easily. It turned out that she had a UTI and I am told that can have a big impact on behavior in the elderly. Also her doctor explained that like young children they can't explain what they feel and act out or make noises as a way of expressing themselves. In addition, my mother's meds get out of whack now and then as her condition changes and they need tweaking. When they become combative it is very scary - hang in there and try to remember this is not voluntary.