We recently put my dad in a dementia nursing home. Is it better to tell him the truth or that it is temporary?

I would let the Doctors take the blame. My mom fell 3 months ago and has progressive dementia. I know she hates being here..wants to be on her own. But because of the falls I remind her that the Doctors wont let her live on her own again. She has to live with me now in my house. She grumbles about it sometimes..but for the most part I think she excepts it.