Almost half of the dentists who joined the NHS in England last year qualified abroad, official figures have shown.
More courses of treatment were given to children last year
Poland alone contributed 17% of the 2,200 dentists who joined the health service in the year to March 2006.
The NHS Information Centre data shows there were a total of 21,111 dentists - the highest figure for 10 years.
The British Dental Association said the NHS should not rely on overseas staff, and said a disputed contract, brought in this April, may affect NHS numbers.
The new contract sets out how health service dentists charge patients and sets new targets.
Around one in 10 dentists rejected the contract.
The Information Centre figures show there has been a 28% rise in the number of NHS dentists in England compared with 1997, when there were 16,500 dentists.
The proportion who qualified abroad has risen from 40% in 2004-05 to 46% last year.
The figures also revealed that just under half of the adult population - 24.7m people - were registered with an NHS dentist at the end of March 2006, up half a million (2.4%) from 2005.
Almost 64% of children were registered with an NHS dentist, compared with 45% of adults.
The number of dental treatments given to children rose from 6.1 million in 2004 to 7.4m in 2006, while the number of adult courses of treatment fell from 27 million in 2004 to 25.8m in 2006.
Professor Denise Lievesley, chief executive of the Information Centre, said: "These figures provide a long term view on dental workforce and activity under the old NHS dental contract.
"Major changes in the NHS contract came into force from 1 April 2006 and the impact of this on dental provision will be reflected in a report to be published in October."
The British Dental Association's chief executive, Peter Ward said: "The figures published today don't tell the full story with many patients still struggling to find a dentist.
"We welcome dentists from overseas but this is only a short-term solution to the shortage of dentists caused by poor workforce planning in the past.
"We must also wait to see the impact of the new NHS contract, given that one in 10 of the new contracts were rejected by dentists and around one in four are in dispute."
Liberal Democrat health spokeswoman Sandra Gidley said the figures did not take into account the "thousands" of dentists who have left the NHS because of the new dental contract.