Where to find a dentist specialized in 90+ year old people?

Don't know that there are any geriatric dentists out there but the guy my mom uses is very good with her. She's 83 with not many teeth left. He doesn't do complicated and expensive bridges, crowns, implants etc. He does the most basic repairs so that she is able to eat and doesn't have toothaches and infection.

Try asking at nearby nursing homes, they may be able to refer you to someone they are familiar with.