Nearly six out of 10 high street dentists are threatening to reduce their NHS commitment or quit the health service completely.
NHS dentists are in short supply
A British Dental Association survey found dentists had little confidence in government plans for reform for 2005.
Official figures show that half of people in England are already without access to an NHS dentist.
But health minister Rosie Winterton said the situation had improved since 1997.
The consultation exercise found just 2% of high street dentists said that they would increase their NHS work on the back of the government's proposals.
About 16% said that they would stop providing NHS dentistry altogether.
The reforms, due to be implemented in April 2005, signal the biggest shake-up in NHS dentistry for over half a century.
They will see dentists working under primary care trusts and local health boards rather than under nationally negotiated contracts.
Dentists will also be paid per patient rather than per treatment carried out.
In the early 90s more than 90% of dentists derived 75% or more of their income from the NHS
Currently the figure is just 60% of dentists
But the BDA research found that few among the profession believe that the changes will solve the current problems.
John Renshaw, chair of the BDA's Executive Board, said: "Dentists and patients have had promise after promise that things will improve, but those promises have yet to turn into action.
"We have an NHS dental service at breaking point, with too few dentists, too little investment and too little time to give patients the care and treatment they deserve."
Mr Renshaw said there had been many reports about the difficulties patients faced trying to get NHS dental care.
In February more than 300 people spent the morning queuing in the street in Scarborough to register in person for a new NHS dental service. In total, more than 3,000 people tried to sign up.
Health minister Rosie Winterton told BBC Radio 4's Today programme 3,000 more dentists were available now than in 1997.
"The problem is that many dentists are undertaking private work and the reason they are doing that is the contract that was introduced by the previous government.
"We know there is a problem - we have to train more dentists and we are also undertaking international recruitment because there are immediate shortages that we have to fill."
Tim Yeo, for the Tories, described the findings as "damning" and accused the government of "failing to get a grip" on the situation.
"Tony Blair promised that everyone would be able to see a NHS dentist by 2001.
"The truth is that less than 50% of the population in England have been able to do so. The country believed the prime minister but have been let down."
Paul Burstow, for the Liberal Democrats, said: "The root cause of the current crisis is the botched Conservative contract of the 1990s which alienated dentists and this government's failure to wake up to the scale of this problem earlier."
The BDA estimates that only 100-200 of the UK's 21,000 High Street dentists run a purely private service at present. However, many others derive a significant proportion of their income from private work.
The association's findings, based on responses from 7,000 dentists, have been submitted to the Department of Health.