My 5 year old daughter has a cavity in her last lower back molar tooth.
My general dentist diagnosed it with a digital x-ray and said it was
deep, just nearing the root. We can also visibly see the blackness on
the top of the crown.

She will not be eligable for a surface numbing, and will require local
anethesia to numb her mouth during the procedure. Needless to say, I'm
concerned about the local anethesia for a five year old and about her
temperment during the procedure. Is it safe for a child her age?

My general dentist said we could use him for the filling, or go with a
pediatric dentist whom might be better for this. Would you choose a
general or pediatric dentist? Why?

Also, why would a child so young get a deep cavity like this? She
brushes regularly.