This is the CodeSystem that contains all the codes in American Dental Association Area of Oral Cavity System (http://terminology.hl7.org/CodeSystem/ADAAreaOralCavitySystem) and American Dental Association Area of Oral Cavity System (http://terminology.hl7.org/CodeSystem/ADAAreaOralCavitySystem). E.g. what you have to deal with if you get resources containing codes in either of them