Tories fear NHS dental overcharge
Problems with the NHS dental contract may mean patients are being overcharged by £109m a year, the Conservatives say.
The party claims its figures suggest that millions of visits by patients in England may have been unnecessary.
Some dentists find ways to charge twice for treatments which would normally incur a single fee, the party says, an accusation the profession disputes.
Health Secretary Alan Johnson said the claim that dentists were "fiddling the system" was "wrong".
The NHS dental contract, designed to introduce a fairer and simpler way of paying for treatment, has been the subject of heavy criticism since its arrival in April 2006.
Millions of people in England remain without an NHS dentist, and dentists' leaders say it still does not sufficiently reward their work.
The government has already pledged to investigate reports that some dentists were exploiting loopholes in the charging mechanism, but the Conservatives have now produced figures which they say hint at the extent of the problem.
The figures reveal how many patients went to see their dentist for chargeable treatment within three months of their first visit.
Under the contract, if patients go back within a two-month period - perhaps to complete a course of treatment - that attracts only a single fee.
However, the Conservatives say that many of these patients have returned to complete their treatment after the two-month deadline - perhaps in some cases simply so that a second fee could be charged.
As national guidelines say there is no need to give patients routine check-ups on more than a quarterly basis, there is a good chance that many of these fees are unnecessary, they say.
Across all of England's primary care trusts, on average 18% of charges - more than six million visits - involved a patient re-attending within three months.
The total cost of these was £109 million, they said - almost a quarter of the total of £475 million paid by patients every year.
Shadow Health Secretary Andrew Lansley said "the principle should be payment by results instead of payment for activity".
"The blame here lies with Labour's botched dental contract, which incentivises dentists to increase the number of charges to patients and has led to such drastic cuts in the number of people being able to find an NHS dentist," he said.
"At the moment we're all losing out - those who do have a dentist are paying wrongful charges, and those who don't are being blocked from finding one because there aren't enough appointments left."
However, the data obtained by the Conservatives does not discriminate between unnecessary visits and fees, and patients who legitimately need treatment carried out to these timescales.
The British Dental Association (BDA) said there were a variety of reasons why it was necessary for patients to return outside the two-month deadline.
My dental service is NHS/private. If you need work done and it happens to be cheaper going private, they will tell you.Steve, UK
A spokesman said: "Patients' treatment needs vary from individual to individual and there are a number of reasons why it can be appropriate for them to be seen more regularly than the design of the system allows for.
"Such circumstances include addressing unexpected problems after treatment or the clinical needs or wishes of patients dictating that treatment is best provided in phases."
"If cases of patients being recalled inappropriately are identified, primary care trusts will need to talk directly to practitioners to identify the reasons why this happening."
He added that the BDA supported the decision to include changes in treatment patterns into a future inquiry into the effects of the 2006 contract.
Dr Anthony Halperin, a practising dentist and trustee of the Patients Association, said: "The whole contract is flawed. What they've done is put temptation in the way of NHS dentists, and some of them, being human, have succumbed to it.
"We've known for some time that some dentists have being bringing patients back again as a way to increase charges. While they shouldn't do it, it's the fault of the system."
Mr Johnson told BBC Radio 4's Today programme he had commissioned an independent review of the dental contract to address certain "issues".
He said it took "time for a new system to bed in", but insisted: "There is extra money going in, it's a simpler system, the proportion of patients being charged is stable at about 27%.
"More dentists are coming in than ever before."