i asked my dentist's receptionist one time when they cancelled my appointment just hours on the morning of my appointment: you charge your patients $100 for less than 24 hours cancellation, should i charge you the $100 late cancellation fee? no, the receptionist said, because the dentist was sick. so, i said, i needed a doctor's note. i really think the concept works both ways. maybe i should write to the dental association about that.
@summerfield in my case i confirmed i wanted the appointment offered, by email, but the receptionist never entered my name in the slot, so i turned up for nothing..