I've gone to El Salvador twice and Guatemala once for medical/dental missions while I was in dental school. In my experience, a general dentist well-trained in the art of exodontia (not necessarily OMFS capable) would probably be the most capable of helping the largest number of people. From what I've seen, there are a lot of cavities to be filled and sealants to do, but most of these mouths have non-restorable, abscessed teeth that need to be taken care of first. The problem is in the quantities. If you are going to treat these people, you have to, in some way, develop a criteria for who would be treated first. I think we would all agree that a person with an active infection is more urgently in need of treatment than a person needing an MOD amalgam. The dental problems in these countries is so bad that by the time you've finished making the first round of "triage," the patients that were seen first would be back to triage stage again.
When I was on these trips, I had the capability to do composite and amalgam restorations in the clinic. It didn't matter, because there were always people in more urgent need of extractions. It really is incredible how fast you can cruise through an appointment when you don't need consents or progress notes. I would typically numb up several people, then extract down the line. As a dental student, I'd probably get through 10 people an hour. The lines never ended. So many more people were in the dental lines than the medical. I never did do a single restoration...
If you ever get the chance to participate in some kind of a medical/dental mission trip, take advantage of the opportunity. I promise that you'll get more out of it than the people that you're helping.
What's on First? and Who's on Second? 
