Braces came off multiple times and took a lot of time to keep going back to fix it. They seemed nice at the beginning but once you're in contract, they don't care about you.
Reception had an attitude, even when you wanted to talk to the dentist for a technical question, she'll try to answer without being a prefessionally trained personnel so you won't bother the dentist.
Accountant is lazy, you won't get a receipt for the payment you give untill you asked for it every time even though the payment is done automatically per month.