When having MOHS why not use the anesthesia that dentists use to numb your gums?

I think that you're actually asking about the type of "block" used to numb the face prior to Mohs excision. This mainly depends upon the area of the face that is being operated on and the Dermatologist's experience with dental blocks. In my Denver facial plastic surgery practice I perform alot of Mohs reconstruction and use blocks whenever possible to numb large areas with a single injection. However, some areas of the face cannot be blocked because sensation is supplied by more than a single nerve. For parts of the forehead, inner part of the cheek and lips, blocks can be highly effective. However, some surgeons are not familiar with how to safely perform these blocks. You can certainly ask your Mohs surgeon if a dental block would be helpful prior to your procedure. I hope this information is helpful.Stephen Weber MD, FACSDenver Facial Plastic Surgeon

The anesthetic agent used by dentists and Mohs surgeons is most often lidocaine (brand name Xylocaine).  A topical anesthetic cream can be used to minimize the pinch from the injection but the solution does cause some discomfort as it is injected into the deeper tissue.  The topical anesthetic would not work to relieve that discomfort.

Frequently, the type of anesthetic used is the same, referred to as lidocaine or xylocaine. Dentists frequently perform a nerve block to get anesthesia, whereas usually Mohs surgeons would use local infiltration. The difference is where the anesthetic is injected. Best way to look at it might be to think of the shape of a tree. In a nerve block it is like the medication is injected around a tree's trunk or large branch. With local infiltration it would be like injecting on a smaller branch and just impacting the twigs and branches on that smaller branch. Sometimes Mohs surgeons might use a nerve block, but usually local infiltration works well without anesthetizing a larger area. Hope this helps.