Just speaking for myself here, but I would simply ask the dentist and any other staff treating me to mask in my presence. I cannot imagine they would decline.

We have been traveling and living as normally as possible this past year and a half, even flying (masked) and have this far escaped illness. Right now my kids are stating away due to them having respiratory issues, and I'm missing them but appreciate their carefulness.
I have had many medical appointments in December, and all of the docs and physical and respiratory therapists masked while in close proximity (during exams and tests).
Sue