Access to NHS dentistry is a long-running problem
Long-standing problems over access to NHS dentists in England are being linked to a rise in patients admitted to hospital with dental abscesses.
The number of hospital admissions for abscesses has nearly doubled in eight years to just under 1,500 a year.
Bristol University researchers said the increase represented a "major public health problem" and seemed to be caused by changes to the dental contract.
The government said recent reforms were aimed at improving the situation.
The 1990 contract led to many dentists increasing the amount of private work they did in a row over pay.
It meant an increasing number of people struggled to get on to dentists' lists - from 1994 to 2004 those registered fell from 23m to 17m.
The team analysed official NHS data and found that there were 750 admissions in 1998-9, but by 2005-6 that had risen to 1,431, the British Medical Journal reported.
The team dismissed the suggestion that poorer oral health was to blame, pointing out that the average age of the patients, at 32, was too young to support that theory.
Instead, researchers said changes to the dental system could be the cause, as access to dental care was an issue even before the most recent change to dental working practices in 2006.
Lead researcher Steven Thomas, a surgeon who treats dental abscesses, said the rise in admissions was a "major public health problem".
"Most serious dental infections are preventable with regular dental care. Indeed, this is the rationale for regular dental check-ups.
"Changes in service provision could, therefore, have resulted in reduced provision of routine dental care and access to emergency dental care.
"These changes might explain the rise in surgical admissions for dental abscess."
Professor Damien Walmsley, the scientific adviser to the British Dental Association, said: "These findings are extremely concerning."
The government introduced a new contract in 2006 to try to improve access to NHS dentists, but latest figures have suggested as yet it has made little impact.
Nonetheless, the government is confident the reforms will work.
The contract has been designed to make NHS work more attractive by allowing dentists to spend more time with patients to get away from the so-called "drill and fill" culture.
A Department of Health spokesman said the new contractual arrangements "set out to tackle" the issues raised.