Neck lift and lower face lift first or cosmetic dentistry?

It depends on the kind of cosmetic procedures you are considering. Your lack of teeth show may also improve with a lip lift as our upper lip gets longer and starts hanging like a courtain over the upper dentition. Only a physical examination will determine if this is the case in you.Otherwise, there is no preferred order of treatment for you. This is different in patients who are considering multiple dental implants which will impact the facial anatomy. Then it is advisable to have the dental reconstruction done first followed by the facelift.

It doesn't matter whether you have dental work or face and neck lift first.  They do not interfere with each other.