I call it "verified diagnosis". We use game theory to extract the truth. Think prisoner's dilemma for dentists.

Edit: Not in US, but building planning to launch there. You can't practice dentistry in US if you haven't got US diploma. However, diagnostic dental work (at least in some states) is exception to this.

Too bad there is no safe or easy way to get X-rays just by sending a home kit to customers.

I don't think that's necessary. Most people living in urban areas have x-ray practice in a close vicinity. Even for those who don't, a home kit wouldn't justify the cost. You want to make a standard high quality x-ray set 2 times a year. Professionally done. Most of people on the planet can make a trip to a city 2 times a year.