A dental surgery in the town of Marsh Hollow has installed a camera above its treatment chair, angled to capture the patient's face during procedures. Patients are encouraged to react to their own treatment in real time for the surgery's channel, which publishes the footage the same afternoon.

The camera, which the surgery has named the Comfort Cam, records continuously. A screen beside the chair plays the feed back live, so patients can adjust their expressions while the drill is running.

Mr Tennyson Grubb, the principal dentist, said the idea came to him during a routine filling. "I noticed patients were pulling faces anyway," he said. "It seemed a waste not to collect them. We are a small practice. Reach is reach."

The consent form

Patients are asked at reception whether they would prefer to be filmed in widescreen or portrait, and whether they intend to cry quietly or openly. Those who decline to appear are offered a blurred option, in which only their discomfort is shown and not their face.

A second form asks patients to nominate their preferred reaction style from a list the surgery has drafted, which includes "stoic", "trembling", "the slow realisation" and "brave".

Mrs Odile Pratt, who attended on Tuesday for a molar, said she had prepared for her appointment by watching the channel's previous patients and taking notes. "I didn't want to let the practice down," she said. "My predecessor in the chair was very good. He did a whole slow head shake." She described her own performance as "a bit flat, mostly wincing", and said she had asked to come back for a follow-up.

The waiting room

Patients in the waiting area are now filmed reacting to the reactions of the patients in the chair, in a segment the surgery calls The Gallery. Footage from The Gallery is used to promote the following week's appointments.

Mr Grubb said the surgery has no plans to stop. "People say a dentist's chair is a place of quiet fear," he said. "But fear is engagement, and engagement is what the algorithm wants. Also we found a cavity in a man's wisdom tooth purely because he turned his head for a better angle. Medicine advances."

The surgery's next video, scheduled for Thursday, is a root canal that Mr Grubb described as "a two-parter".