Dentists will be required to refund £120 million to the health service because they failed to treat enough NHS patients last year, The Times has learnt.

About half of dental practices have fallen short of targets for NHS treatment agreed with local health authorities, meaning dentists will have to pay back tens of thousands of pounds each.

In the latest repercussion of the troubled dental contract, clawbacks are threatening to put some practices out of business and may persuade many more dentists to leave the NHS, the British Dental Association (BDA) says.

Thousands of patients across England are still said to be struggling to find NHS treatment, and yet about five million fewer treatments were carried out in 2007-08 than were budgeted for by the health service, figures show. This represents a 5 per cent rise in the amount that dentists will be expected to pay back, in the second year of a new pay contract that has been heavily criticised for creating a “drill and fill” culture and failing to improve access to NHS treatment.

In the past dentists were paid a fee for each treatment they provided but, under the dental contract introduced in 2006, they receive an annual income for carrying out an agreed amount of NHS work, measured in “units of dental activity” (UDAs).

Dentists, however, say that the only way to reach targets is to take on quick jobs, such as extracting a tooth rather than carrying out root canal surgery to save it, because both treatments have the same UDA value.

About 1,000 dentists opted out of providing NHS services when the new contract came into force, meaning that 900,000 fewer patients were seen in 2006-07 than under the old system, a report by MPs found this year.

The Health Select Committee suggested that dentists were being set unrealistic targets for NHS work and that a failure to meet targets in the first year of the contract meant a loss of revenue for the second.

The latest figures, obtained under the Freedom of Information Act by DPAS, a company that provides private dental plans, suggest that some regions have experienced particular problems.

In Leicester, for example, more than 50 per cent of UDAs have not been delivered and 21 dental practices face repayments of £50,000 or more.

Across the country, 89 per cent of primary care trusts responded to a survey that found a total of 411 contracts where targets were missed by £50,000 or more.

Peter Ward, the chief executive of the BDA, said that dentists who failed to meet their targets in the first year were likely to have failed to do so again last year, creating a “roll-over effect”.

He said: “Once again this highlights problems with a target-driven contract that contains one crude measure of performance, which has long been criticised by the profession and patient representative groups.”

Quentin Skinner, the chairman of DPAS, said: “For those dentists who fell rather short of the mark, the future for them in the NHS certainly looks bleak.”

Barry Cockcroft, the Chief Dental Officer for England, said: “The Government is committed to growing NHS dental access year on year. This is why increasing the number of patients seen has been made a national priority for the NHS – and backed up by an uplift in funding of 11 per cent (£209 million) this year.”

“The increased focus and funding is already starting to show results, with 655 more dentists working in the NHS in 2007-08 than the previous year and 36 million courses of treatment delivered compared with 35.1 million in 2006-07,” he added.

Mike Penning, a Conservative health spokesman, said: “It is extraordinary that [these clawbacks are] happening at a time when over one million people have lost access to their NHS dentist in the last two years. These figures show, yet again, why we need to rip up Labour’s botched contract and move towards a registration system based on clinical need, one that is targeted at preventing dental ill health rather than reacting to it.”

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