in that case let me help narrow your vision a bit.
avoid systems such as Laserdenta, dentalwings, and for obvious reasons Cerec.
most CADCAM companies have hardware and software components: 3shape makes scanners and software where exocad does not. exocad expects you to have a scanner and will expect you to know how to plug in the software to it. it is the system people go for after having bend over backwards with another cadcam company and regrettably can't iron out its issues.
3shape and companies like Lava or Nobel will try to sell you a package. a scanner and a computer and a mill, and try to be your best buddy for a slice of your pie.
if you only want to get into scanning and designing your own units you're in a much better position to evaluate your finished product than someone who bought all the components at once and is now pulling hair out trying to determine where his shortcomings are.
in both exocad and 3shape you are openended. you can plug in a mill or printer later if you choose, with very little needed to get it running. neither are systems you'll be "done" with in 3-5 years time. for exocad however you will need someone to help you associate your scanner with the design suite, so if you go down that road you're going to have to do some scanner number research - certain companies offer their scanners sans software such as Medit or Steinbichler. then again some retailers offer those scanners plus a copy of exocad with 1 year free updates (you pay for updates past that point)