Thousands of patients who are losing their dentists are not guaranteed another NHS place elsewhere.
The Littlemore Dental Practice, in St Nicholas Road, closed on Friday and the ADP surgery in Cowley Road, Oxford, is to close tomorrow, with about 9,500 health service patients on their books.
Both practices have said existing NHS patients were welcome to attend their sister practices in Abingdon and Kidlington, but patients who did not want to travel that far must turn to Oxford City PCT for help in finding a new health service dentist.
The PCT currently has a list of just three dentists in the city who are taking new NHS patients, and some of those surgeries have agreed to take on patients from the two closed practices.
But they could not guarantee there would be enough NHS dentists to cater for all the patients set adrift by the closures.
A spokesman said: "The PCT is hopeful that we can find those patients who don't want to move with ADP a new NHS dentist closer to Cowley.
"The PCT is able to commission dental services for patients and we have made provision for ADP's NHS patients to be served elsewhere."
She said the same would be true for patients in Littlemore, which closed last week after dentist David Duffy decided to concentrate his energies on his Abingdon practice.
ADP's operations director Steve Frampton said the closure of the Cowley Road surgery had been a joint decision with the PCT following the new dental contracts introduced in April.
The new system sees dentists paid on the basis of work done in the previous year, not for each treatment they give.
Mr Frampton said: "The contract we had in the Cowley practice was not sufficient to maintain the practice there."
But patients have reacted angrily to the closure of what they describe as a busy and popular surgery.
Steve Otto lives half-a-mile from the Cowley Road surgery and now faces a six-mile journey to Kidlington, or a scramble for a place with another NHS dentist.
The 31-year-old said: "I'm well annoyed because that was the only dentist that I could actually get in to at the time.
"I can't believe they're closing it because there are so many people that go there and rely on it.
"It is more or less the only dentists around.
"It had only just been refurbished a few months ago, and they added an extra room, so I thought they would be there for a while.
"I thought they were the saviours of Cowley but obviously not."
He added: "It's not their fault, it's the Government's. It's all the cutbacks."
Patients from either surgery can call the PCT on 01865 226818 for a list of practices who may take them on.
For a list of dentists taking new NHS patients call the PCT's Dental Enquiries line on 01865 226785.
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