The NHS is struggling to fund specialist dental treatments in many areas, according to a survey of primary care trusts.
The new dental contract has been widely criticised
More than half said they had trouble funding crowns, bridges, root canal work and orthodontics.
The Patients Association, which carried out the survey, said patients faced "unnecessary pain and cost".
Ministers say that increasing access to NHS dentistry remains a top priority and more dentists had been recruited.
Overall, the survey found an "unacceptably wide variation" in dental services across England.
The findings come just 24 hours after it was revealed that younger dentists are performing less NHS work than in previous years.
The Patients Association carried out the survey as part of a wider review following the introduction of a new NHS dentistry contract in April 2006.
Under the deal - designed to stem the flow of NHS dentists into the private sector - three levels of payment, ranging between £15.90 and £194, replaced more than 400 different tariffs and treatments.
The association says that 1.3% of the population still has no access to NHS dentistry, and people remain confused about the new system.
Orthodontics: Treatment of biting problems caused by irregular teeth or disproportionate jaw relationships
Periodontics: Care of the tissues surrounding and supporting the teeth, especially the gums
Endodontics: Care of the tooth pulp, including root canal work
The number of complaints to primary care trusts (PCTs) is rising, with the majority of concerns surrounding the charging system, orthodontics or finding an NHS dentist.
Three-quarters of all English PCTs replied to the survey, and 59% of those said they had difficulty funding orthodontic, periodontic and endodontic treatment.
The association said that this meant delays for patients, which, for children awaiting orthodontic treatment, might make the whole exercise pointless.
Katherine Murphy, its director of communications, said: "Our survey shows that the new contract is compounding previous dental policy failures, and too many patients are being excluded from continuing dental care.
"There is no reason - health or political - why teeth should be treated any differently to other parts of our bodies.
"The current situation is leading to unnecessary pain and unnecessary private cost for too many patients in the UK."
She called on the government to improve preventative dentistry care, and ensure that all areas had the same level of access to specialist treatments such as root canal surgery and orthodontics.
The British Dental Association is also critical of the new contract.
Lester Ellman, who chairs its General Practice Dental Committee, said: "The new system focuses on targets, not patients."
"It is flawed and has failed to encourage a more preventive approach to care. We want a range of performance indicators which look at patient experience - quality and oral health outcomes."
Health Minister Ann Keen said that the drive to recruit new dentists had added 4,000 to the NHS since 1997.
She said: "Increasing access to NHS dentistry is a top priority for this government and that is why we announced last year that we would increase funding in this area by over £200m, and have ringfenced this to ensure it is spent on dentistry alone."