I had my the people who wrote mine address it to "Medical School Admissions Committee". Besure the letter also includes your social security number, AMCAS ID, and TMDSAS ID (if applicable).
Everytime I have seen it referenced, it is AMCAS ID. But, they would probably know what you meant either way.
The point is to give them redundant ways to locate your record. If you do it this way, they will have your name, social security, AMCAS (AAMC) ID, and TMDSAS ID.