Here's a good list: http://rankings.ft.com/businessschoolrankings/online-mba-2012-listing

Do you want to do something with a specialization in the medical field? If so, check out the online program at George Washington University or the one at Northeastern - while many of the electives that make up these specializations apply specifically to hospitals and other parts of the healthcare profession, the insights from the overall specializations could be valuable for somebody in a dental office.

Also, Oklahoma State/Spears offers an online program with a dentistry focus specifically.

If you don't need something specifically with a medical focus, then try an accredited general degree. UNC, IE, IU Kelley, Warwick, Florida/Hough, Aston... There are quite a few.

Thank you Duncan and Ralph for your expertise.
Ralph, thank you for your detailed suggestions.