After 7 weeks, the initial recover period has been completed but you will still be healing. In general, when recovering from a facelift, you should avoid the following:
1) Strenuous activity (for the first 4-5 weeks).
2) Stretching or pulling the skin, where tension is put on the incisions.
3) Smoking (for 6 weeks before and after surgery)
4) NSAIDS, Ibuprofen, Vitamin E, fish oil, and other over the counter supplements that can cause thinning of the blood. (For 2 weeks following surgery)
Opening your mouth in a dentist’s chair should not put too much tension on your skin or have an effect on your result. In general, I would recommend avoiding anything that is not comfortable while you are healing. I would recommend communicating with your dentist and explain to them you recently had surgery. I hope this helps, and best of luck to you.