how to fill small gap between slab & wall

I am redoing my basement, and need to know what to do about ceiling tiles. I am thinking about reusing as many of the old tiles as I can (they are standard 12" tiles put up with staples) Just going to pull staples and save all tiles that are in decent condition, the problem I have is this, the existing ceiling got damaged because I need access points for furnace dampers, water shut-off's ect. and the tiles were put up with screws in these locations. I am wonderign how else these removable tiles could be put up, or what other options I could use in place of these removable tiles. The hole doesn't need to be bigger than the size of the tiles. I had thought about a drop ceiling, but the ceiling is low as it is. Any help you can give would be greatly appriciated.

What is the best method to use for roof top ventilation on an existing concrete tile roof. I already have adequate eave ventilation and need some way for the air to exit.