Dentists are overcharging patients and not informing them about NHS treatment to which they are entitled,  an undercover investigation has found. The three-month probe found some dentists are pressurising patients to go private – even though they could get the same treatment far more cheaply on the NHS. In one case, a patient was given a quote for root canal work which was almost four times the non-private cost. The shocking findings were made by Channel 4’s Dispatches team. They sent seven members of the public for an NHS check-up at surgeries which offer both NHS and private treatment. After an average of 15 minutes in the chair, six out of seven came out having been recommended to have some treatment privately – mainly hygiene work. Instead of getting an NHS-standard scale and polish for £16.50, they were quoted prices to go private. Another visited three surgeries, seeking root canal treatment which should cost £198 on  the NHS. Instead, he was quoted private rates of £678, £598  and £725. Dr Anthony Halperin, a dentist and member of the Patients Association, said: ‘I’m very concerned that they all seem to have suggestions of having private treatment. ‘If the patients go in as NHS patients and are told work is not available under the NHS which is available under the NHS, then the dentists are in breach of their contract.’ The Coalition plans to renegotiate Labour’s 2006 dentistry deal. The Truth About Your Dentist will be broadcast on Channel 4 at 8pm tonight.