There actually is a scanner that can eliminate the need for the "goo" of the molds.
Here are several different systems --
http://www.orthodonticproductsonline.com/2013/07/going-digital/
But, not every orthodontist has moved forward and is using that technology.
And it doesn't take the place of x-rays.
參考: Orthodontic assisant with over 32 years of experience.