Reforms of NHS dentistry mean some patients are receiving substandard care, critics claim.
Complex procedures include crown and bridge work
Dental Laboratories Association figures show a drop in the number of complex treatments, like dentures, carried out since the new contract began in April.
The DLA says financial rather than clinical concerns are driving decisions - to the detriment of patients.
But the government says the new contract was designed to cut unnecessary complex treatments.
'Dark Ages of dentistry'
The chief dental officer, Barry Cockcroft, said dentists will still act "ethically and clinically" in the best interests of the patient.
Speaking on BBC Radio 4's Today programme he refuted suggestions by DLA chief executive Richard Daniels that the service was "going back to the Dark Ages of dentistry".
Mr Daniels argued that his association had comments from "some of the most vulnerable" patients who had required dentures and instead were given tooth extraction.
He blamed the new contract, which does not record the specific treatment carried out.
"For example, if you had a tooth missing under the old contract very regularly you would have received a single crown.
"Under the new contract you'll be finding you'll get a one tooth denture and the cost of those are significantly different yet the dentist's income will still be the same," he told the programme.
Mr Cockcroft said the DLA's evidence was "anecdotal" and said the government's pilot project found patients were pleased with the new system.
It found a drop in intervention, with no impact on patients, he said.
"The vast majority of dentists will actually still do what is completely right for their patients," he added.
He said the old contract was designed to deal with a completely different climate and that the oral health of the nation had "vastly improved".
Earlier he said the new contract was designed to give dentists more stability - and the same money for treating fewer patients.
It meant they did not have to rely on a "drill and fill" culture to maximise their income.
However, if dentists do not fulfil their work quota, their employer, the Primary Care Trust, can ask for some of their wages back.
The DLA, a professional body for dental laboratory owners, says this pressure may be affecting the treatments dentists are providing, with some doing fewer time-consuming, complex procedures.
It revealed exclusively to BBC Breakfast that it had seen a 57% reduction in complex "Band 3" dental treatments - such as crowns and dentures - on the NHS compared with the old dental contract.
Yet on Denplan, where dentists do not pay for laboratory work but patients do, the rate of Band 3 work has remained unchanged over the same 12-month period.
The figures show that the private market is not growing at the same rate at which the NHS is decreasing.
It could be that patients are missing out on treatments altogether.
The DLA believes 3%-5% of the dental work is being shipped abroad.
Richard Daniels, DLA chief executive, said: "The current contract is forcing dentists to make prescription decisions based on financial resources rather than clinical need.
"My concern is that, with such a dramatic reduction in complex treatments, some of the most vulnerable people in society are suffering.
DENTAL TREATMENT BANDINGS
Band 1 - simple scaling, examination, repairs
Band 2 - tooth extraction, root canal work
Band 3 - veneers, dentures
"The Department of Health must act now to stop the decay of our dental service."
Peter Ward, chief executive of the British Dental Association, said it was too early to say if there had been a change in the amount of complex treatments being performed by NHS dentists.
But he said: "What we do know, is that the crude, target-driven contract introduced in April 2006 is creating problems for dentists and patients across England and Wales.
"Dentists are highly-trained healthcare professionals and should be treated as such, rather than being left chasing targets."
Anthony Halperin, chairman of the Patients Association and a private dentist, said: "I am convinced that this contract is not to patients' advantage.
"They are not being treated as efficiently as they were under the old system and they are paying more for it.
"Dentists are so driven by hitting targets that there is no incentive to carry out complex work that might be best for the patient."