Dentists have been told not to re-use instruments for root canal work because of a possibility they could infect patients with variant CJD.
The risk is only theoretical
The government's chief dental officer for England said there had been no cases of transmission, but research had shown a potential risk.
The recommendation is based on guidance from the expert Spongiform Encephalopathy Advisory Committee.
It applies to instruments known as files and reamers.
These are used in endodontic procedures, most often to remove dead or damaged tissue from the root canal of a tooth.
Dr Barry Cockcroft, the chief dental officer for England, said: "There are no reported definite or suspected cases of vCJD transmission arising from dental procedures.
"This new guidance to dentists is purely an extra precaution. The public should continue to attend their dentist as normal."
Infection rates unclear
There are approximately one million NHS endodontic treatments every year in England and Wales.
Since 1996 there have been 165 cases of vCJD. There is no current evidence of vCJD being transmitted by any form of dentistry.
Almost everyone is at some risk of being infected with vCJD due to dietary exposure to BSE.
However, the proportion of people carrying infection is highly uncertain.
Research suggests that this may be between 1 in 1,400 and 1 in 20,000 people, though it may well be less for some age groups.
It is also not clear how many of those carrying the infection are likely to develop symptoms of vCJD.
Even if dental instruments had been used on someone carrying the infection, it is not clear how great the risk of vCJD being passed on would be.
In lab tests, scientists have successfully infected mice with the related condition BSE after exposure to contaminated dental instruments.
However, the risk of a similar infection taking place in human dental patients remains at this stage theoretical.
Peter Ward, chief executive of the British Dental Association, said: "Dentists take patient health and safety seriously and will apply this latest guidance robustly.
"The extremely low incidence of traceable infections originating from dental practice should give confidence that dentistry is one of the safest areas of healthcare."