He's a professional. He genuinely cares about your dental health. Most medical doctors enter the profession because they genuinely want to help people, not exploit them for bucks. And prevention is very often the best method of help.

Compare him to the programmer who creates an extensible open framework, as opposed to the guy who throws together a dense hack that only he understands. The latter could be said to be acting more in his own interest, but the former is more dedicated to his profession and the greater good.