Patients will be getting sub-standard care under dentist reforms being introduced, a survey says.
The dental reforms start on 1 April
Just 2% of the 684 dentists polled by the Patients Association said the new contract which starts on Saturday will lead to care patients deserve.
And only 4% said the new system of fees, designed to make pricing more simple, offered better value for money.
Meanwhile, dentist leaders warned many may opt out of the NHS by refusing to sign the contract.
Under the new system, dentists are supposed to be given more time to carry out preventative work while the pricing system is being simplified.
The changes mean the old system of over 400 different charges for dental work will be replaced by three bands - £15.50 for a check up, £42.40 for a check up and filling and £189 for more complex work such as crowns.
Dentists quizzed said they were still not being given enough time to do preventative work - under the terms of the deal there workload is supposed to be be cut by 5% to enable them to spend more time advising patients about good teeth care.
Dr Anthony Halperin, trustee of the Patients Association, said: "The survey's findings paint a bleak picture for NHS dentistry.
"The government needs to urgently reconsider its approach to dentistry in the UK so that proper access to long-term dental care can be assured for those patients who need the NHS option most."
Dr Halperin agreed with the British Dental Association that many dentists may not sign up to the new contract.
Susie Sanderson, chair of the BDA's executive committee, has written to Tony Blair challenging his assertion in parliament last week that the majority of dentists would come on board.
In her letter, she said: "We will have to wait and see how many dentists sign up by 1 April, but we would counsel against any interpretation that equates dentists signing at this stage, with a secure future for NHS dentistry."
She said there needed to be a review of the impact of the new contract in the near future.
But Health Minister Rosie Winterton said the survey did not reflect the true picture.
"The early signs are that the vast majority of dentists will sign up. If dentists choose not to, the local NHS will use that funding to buy services from other dentists."