One in 10 dentists has rejected the new NHS contract outright, and many more have registered objections, a British Dental Association survey suggests.
Many dentists are unhappy with the new arrangements
It says about 60% of those who signed did so "in dispute" and will continue to contest the terms while providing NHS care - for the time being.
The government argues the contract will help tackle the shortage of NHS care.
But the BDA said it will create even more barriers to patients receiving treatment on the NHS.
Under the new system, to be introduced in England and Wales, 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.
However, the BDA argues that the targets set out in the new contract are unachievable. They say it will not increase the time they can spend with patients, or lead to an improved standard of care.
The BDA survey of local dental representatives found 90% of respondents believe access to NHS dentistry will worsen.
It is estimated that under the new contract, to be implemented from 1 April, dentists will receive an average annual income of £80,000.
But this figure is vigorously disputed by dentists, who argue that expenses, which are spiralling ahead of inflation, will eat substantially into profits.
Dr Susie Sanderson, chair of the BDA's Executive Board, said: "This survey reflects once again the high levels of anxiety and confusion that both patients and dentists are experiencing.
"It highlights the uncertainty into which the government's reforms have plunged NHS dentistry.
"It is clear that even those dentists who are signing the contract are desperately concerned about the future.
"Their morale is low and many are signing in dispute."
The BDA has written to the Prime Minister stressing the importance of monitoring the impact of the reforms - and rectifying any flaws which become apparent.
Dr Sanderson said: "We are very worried about the future of NHS dentistry, particularly as we go through the next few years where the funding for NHS dentistry will no longer be ringfenced at local level.
"We would like to see some serious investment in NHS dentistry. We would like to see dentists being given time to spend with their patients, particularly on issues such as prevention, and to make sure that patients are getting the care they deserve."
Health minister Rosie Winterton said: "The public have every reason to be confident in the future of NHS dentistry.
"This survey covers less than a third of LDCs and the figures we are receiving show that the vast majority of dentists are signing up to the new contracts.
"If dentists choose not to sign up, the local NHS will use that funding to buy services from other dentists.
"However, all the current indications are that most of the dentists leaving do relatively little NHS dentistry, and account for only a small fraction of NHS services."
However, Shadow Health Secretary Andrew Lansley said: "The government's mishandling of this contract will further damage patient care and the prospects for the future of NHS dentistry."
If dentists sign their contract in dispute, their case will be considered through an appeals procedure set up by the Family Health Services Appeal Authority.
Of the 109 local dental committees in England and Wales, 35 responded to the BDA survey.