Thousands of children are to be denied regular check-ups on their teeth, leading to more decay and extractions, because of the crisis in NHS dentistry, leading figures in the field are warning.

One of Britain's most respected dental experts, Professor Liz Kay, of the University of Manchester, said chaos surrounding new contracts for dentists means parents will not be able to find anyone to care for their children's teeth.

'It is of great concern that you could be seeing more children in pain because they are not taken regularly for check-ups,' Kay said. 'This new contract is moving in totally the wrong direction. Instead of encouraging dentists to do early check-ups to prevent decay, it simply means you treat disease by doing more extractions.'

The reforms, which take effect this weekend, mean that, instead of being paid for each item of work they perform, dentists will receive a 'block contract' from their local primary care trust, committing them to a set number of 'units' of treatment over a year.

Dentists say they are not being given enough time to see patients properly or to tell them how to protect their teeth. Some have been offered far less NHS work than they wanted. Others, who treated only children on the state service and took adults as private patients, are being told this must stop.

It remains unclear how many dentists will continue to do NHS work. Many are likely to refuse to sign the contracts and will work only privately.

'Our clinics are already full of children who need fillings,' Kay said. 'The idea that this queue might lengthen and that you might see more small children coming in with decay and toothache is terrible. If children come in with severe decay, some of them end up going under general anaesthetic to have them removed. That's what will happen if they can't get preventive dental care.'

The chaos surrounding dentistry emerged last week when the helpline service, NHS Direct, was inundated with thousands of people asking if they knew where they could find an NHS dentist in their area. One official said: 'It's a nightmare. We've been taking so many calls from patients who've suddenly found out the dentist will no longer see their kids on the NHS. Our information isn't completely up to date, so we have to tell people to ring around surgeries themselves.'

It is not known precisely how many adults or children may find themselves without an NHS dentist, but by the end of last week many practices had posted notices on the NHS Direct website saying they were not accepting new NHS patients.

Ministers continue to insist that the new system will protect patients better. The Health Minister, Rosie Winterton, said last week: 'Early claims that dentists would leave the NHS in a mass exodus are proving unfounded, as early indications from the local NHS show that the vast majority of dentists are signing up.

'There are measures in place with every primary care trust to ensure re-provision of services in those relatively small number of cases where it is necessary. In fact, many PCTs are already doing this with great success, for instance in Cumbria and Lancashire, in Plymouth and in Shropshire. We are confident these reforms give the NHS a firm basis for improving patient care.'

The British Dental Association said one in 10 dentists had rejected the new contracts and would withdraw from NHS work, while many more have registered objections.

The objectors say the new system is flawed, and many of them will lose income if they accept it because the contract does not give them enough time with patients, nor reward them for advising people how to care for their teeth.

Around 60 per cent of those who signed did so 'in dispute' and would contest the terms under an appeals procedure while continuing to provide NHS care, the association said.

'There is absolutely no way I could afford to go private'

Jo Whitmore has finally found a dentist after a search in her home town of Eastbourne.

The first inkling I had that anything was wrong came in a letter from my local dentist two weeks ago. He wrote that, from April, he would no longer be taking children as NHS patients. We both had an appointment booked next month and we would be charged for missing it if we didn't want to go private.

I felt outraged that our local NHS service, which is just down the road, could be taken away from us in such a peremptory fashion. What about the patients, I thought? I'm a single mother on income support, and there is absolutely no way that I could afford to go privately. A check-up at £20 would be a hefty chunk out of my month's budget. So I rang round the local dentists in Eastbourne, and finally found somewhere that would accept both myself and Louis, but there is still a four-month waiting list. The poor receptionist told me she had been completely overwhelmed by calls, and that they can't cope with the flood of patients trying to find a dentist.

It's not easy to get a child to the dentist in the first place. If this place in the town centre hadn't accepted me, I would have to have taken two buses to get to the next surgery. Aren't dental services meant to be local? I feel really sorry for other families who are frantically searching for someone who will take them on to their books. I can't understand how one of the most basic forms of treatment, dental care, can have been privatised so ruthlessly.