I disagree that it wouldn't be useful. A lot of people with science undergrads have no basic business background, and no experience running (or helping to run) a business. Basic business knowledge is actually quite useful - examples of skills that you would learn in an MBA, that could be applied to your dental practice include:
- Negotiation
- Finance (simple things like PV, EAR)
- Economics
- Accounting
- Marketing
Obviously a formal education is not necessary, as many dentists are without MBAs, but it's the difference between running a business, and running a business well (or, at least better).