A Hopkins dentist who allegedly used another dentist's credentials to prescribe controlled substances and overbill an insurer was fined $20,000 and suspended for at least six months, according to an order made public by the Minnesota Board of Dentistry this week. William P. Rolfe, Jr., has been prohibited by the board from prescribing controlled substances since 2001. That order also prohibited him from administering nitrous oxide and required a female attendant be present while treating female patients. A 2005 order alleged he used a dentist's credentials to bill for dental hygiene services. Rolfe, who denied the board's allegations, must pass a test on state dentistry laws, take an ethics course and report how to use what he's learned in the future. Read Rolfe's current and previous board orders here.