A fake dentist and two assistants have been charged by Czech police after treating dozens of patients using instructions found on the internet. Police said the three family members opened a surgery without a licence in their home in Havlickuv Brod two years ago and treated patients without any "necessary professional knowledge." They added that the 22-year-old man extracted teeth, performed complex root canals and applied anesthesia, drawing on information he had obtained online. All pleaded guilty to a number of charges, police said, and face up to eight years in prison. Police did not say whether any of their patients had complained about their treatment. A 50-year-old woman worked as a nurse, while a 44-year-old man produced prosthetic devices for patients. The illegal clinic treated dozens of patients and made four million Czech koruna ($185,500), police said.