If you are going to the dentist for a routine cleaning, most service dog handlers will ask the hygienist or dentist where in the exam room would be the most convenient place for the service dog to be placed in a down stay so the dog will not impede their job. You will want to ensure for most situations that where your service dog is positioned it is still within easy distance for you to remain holding onto your service dog’s lead.
If you are going to the dentist for fillings, root canals, or any other type of more complex dental procedures beyond just a routine cleaning, it is normally advisable to bring a back up handler for your service dog who can hold onto your service dog’s leash for you while you are having the unpleasant procedure done. If a back up handler is not available then it may be the best for both you and your service dog to leave your service dog at home while you are having your mouth worked on. You will be in no position to control your service dog and your service dog may become concerned with seeing you so incapacitated.