Before you go off on two half-baked professional school boondoggles for half a million dollars you presumably don't have, you should spend some time considering where you hope to end up. What is your ultimate career goal? If you want to be a physician, then you should focus on doing what is necessary to become a physician. Becoming a dentist will do nothing to help you advance down that path.
If your wife's main concern is the financial hit you'll take by going to professional school, then as the other posters have said, what she's proposing would be taking an already bad situation (six figure debt due to med school) and making it much, much worse (even higher six figure debt due to dental *and* med school). Because of the time and expense needed to complete both medical and dental training, this particular dual professional degree combination would be a poor choice for most people. Unless you want to go into oral and maxillofacial surgery, which is a surgical subspecialty whose practitioners sometimes do obtain both a DDS and an MD, you should pick one degree or the other, not both. And even OMS surgeons are not required to have MDs. (Most are dentists with surgical residency training.)
The first step (for both you and your wife) is to educate yourselves about both training pathways so that you have a realistic understanding of what would be involved and what sacrifices your family would have to make in order for you to achieve your goals. As things stand now, the two of you have no ability to make an informed decision about whether you should go to dental versus medical school, never mind both.
Edit: Also, please don't cross post the same thread in multiple forums. I have combined both of your threads here.