Why does my grandfather keep misplacing his dentures and car keys?

I wouldn't expect to find my teeth under the bed either haha. They must have fell and went under the bed. I always misplace my car keys as well. I don't always hang them up on the key holder so I forget where I set them down when I get home. I can usually remember the rooms I had been in though. I think some of that is normal but if there is concern that it might be more than occasional forgetfulness have him talk to his doctor.

Hopefully it's not signs of dementia

very off place to find them. Give him a receptacle next to the bed, for him to place them before going to sleep. How old is he? How many of us, even at a young age, has ever forgotten where you put the keys, TV remote, etc?

1. Habit
2. Ageism

That'll be you someday.

Sounds like dementia. Make a place for him to put his keys and dentures in.