My dear mom will be 102 in October. She is in memory care, and I visit her almost every day. She seems unable to close her mouth. Any suggestions?

If she is in memory care that means that her brain is broken, so I can only guess that perhaps her brain is no longer able to tell her mouth to stay closed.
And at your moms age there should be no reason that she wouldn't qualify for hospice care. I mean really.....at 102 it doesn't take a rocket scientist to know that her time here on earth is extremely limited. Perhaps you may need to contact a different hospice agency, as I'm sure there are many that would be more than willing to offer their services.
Best wishes to you and your mom.

OMGOODNESS 102!!! WOW!! Anyway, she may need hospice now! Have her checked especially if she is in memory care I'm surprise she isn't. Yes it could be she cannot feel her jaw. And for her to see something that is not there is a normal thing for older people. My Mama saw her mother several times before she passed. As one post said, take it one day at a time, one moment at a time and accept that physical things will happen. Hugs

God bless you & your mom. She's a strong lady and survivor. You're a good daughter
[[hugs]]

Has she been examined for any type of occlusion in her teeth?

My dear MIL died aged 99 years and 9 months. She couldn’t speak for the last couple of years. I was with her about three days before she died, and was talking to the aide in her room, saying how sorry I was when I could not care for her at home. It just about destroyed my difficult back, I had to give up long before I wanted. MIL, Dora, started to try to speak, which she hadn’t done for months. It wasn’t intelligible, but I am sure it meant that she had heard and was trying to tell me it was OK. I hadn’t realised that she could still hear so well.

So you may be right that she can still hear you and understand, even if you can’t understand her. Tell her stories of nice things you did together in the past, perhaps she will remember and be happy. Lots of love to you both, Margaret

A stiff jaw could cause this open mouth effect, changes in breathing or swallowing could be factors too.

I think considering such an advanced age, I would take one day at a time.

Each day Mom can chat with you or smile is a blessing indeed ❤️

I would not be surprised to find one morning soon she had slipped away with the dawn 🕊️