Dentists are urging the government to stop "dragging its feet" over reforms of NHS charges.
Dentists say they want to spend more time with patients
Six thousand dentists have written to Health Secretary Patricia Hewitt calling for action.
A new contract, due to come into force in October, has been put back to next April - and details of the changes have not yet been published.
The Department of Health says it will issue its views, following a June 2004 review of dentistry, this week.
There are around 26,000 dentists in the UK, with the equivalent of 13,000 full time dentists working for the NHS.
A dentist working for the health service earns between £65,000 and £68,000 each year, with private dentists earning around the same amount.
But the BDA says dentists who work privately are able to spend more time with patients, and that was one of the main reasons why more and more were opting for private work.
They say NHS dentists see around 50 patients a day, twice as many as colleagues in the private sector.
The BDA says many were also opting to offer lucrative cosmetic dental treatments.
Lester Ellman, chairman of the BDA's General Dental Practice Committee: "Dentists in private practice do not necessarily earn more but spend more time with their patients.
"That is what most dentists working for the NHS want to do."
He said the letter campaign was designed to put pressure on Ms Hewitt to discuss the new charging system with the profession.
"The letter asks for the NHS to put in a lot more money into paying the dentists and changing the working pattern.
"If they make it (NHS work) attractive enough, dentists working in the private sector may move back to work in the public sector."
He added: "Dentists are concerned about the future of NHS dental services for their patients.
"There is a real anxiety that NHS dentistry will disappear unless very urgent and positive action is taken by the government to make acceptable and constructive progress."
He said dentists' fees had been cut in 1992, and the amount spent on dentistry had "steadily been squeezed".
"In 1997 the NHS spent 4.1% of its budget on dental health. Now the NHS spends 2.5%."
Mr Ellman said plans to reorganise the focus of children's dental health from reactive treatment to preventative treatment and to "get dentists off the treadmill" - linked to the new contract - had never got off the ground.
But a Department of Health spokeswoman radical steps were being taken to improve the NHS dental services.
"This is supported by £360 million of new investment. The equivalent of 1,000 dentists will be recruited by October 2005."
She said the government would be publishing its response to the dental review report by Patient's Tsar Harry Caton later this week.