More than 1,500 people waited outside a dental practice on Saturday after the centre took on a new dentist.
They queued for up to seven hours to go on the list of Jimena Colino, a new Spanish dentist at the Fen House Dental Practice in Spalding, Lincolnshire.
Eye witnesses said the queue, which stretched for a mile, was three or four people deep.
Health minister Stephen Ladyman said the government was taking steps to tackle the shortage of dentists.
One man, from Gosberton, told BBC Radio Lincolnshire that he took a friend to register and waited for four hours with her.
"Anyone that was walking that side of the road either to join the queue or to get home had to use the road because the footpath was clogged," he said.
"Our friend eventually got to register at quarter past 12, she'd been there since quarter to eight."
Six dentists have been recruited by West Lincolnshire Primary Care Trust.
Shadow Health Secretary Andrew Lansley said: "Five years ago Mr Blair promised everyone would have access to an NHS dentist by 2001.
"Forward four years, the situation has got worse and all we get is talk about improvements.
"Because Labour failed to agree a new contract with the profession, dentists are voting with their feet."
Mr Lansley said fewer people were now registered with an NHS dentist than seven years ago.