LONDON (Reuters Health) - Oral contraceptives increase the risk of infection and pain following the removal of wisdom teeth, according to research presented on Thursday.

Spanish researchers at Santiago University Hospital reported that tests on 267 women showed that those on the birth control pill were more susceptible than non-users to both postoperative pain and a condition known as 'dry socket.'

In this condition, normal healing of the vacant tooth socket is delayed by the failure of a blood clot to form. Infection instead causes the socket to remain empty.

In the study, pain on the day after the operation was experienced by 30 percent of pill takers compared to just 11 percent of non-users.

Five days after the operation the difference was 14 percent compared to 5 percent. The researchers said these results suggest that the pill may reduce the pain threshold.

The differential was similar when the development of dry socket was compared. Here, 11 percent of pill users were affected compared to 4 percent of non-pill users.

Increased incidences of dry socket in women compared to men can be traced to the 1960s when the oral contraceptive pill came into widespread use. Studies in both 1974 and 1977 recognized this link.

The research was presented at a British Dental Association conference in Manchester and will be published in the conference edition of the British Dental Journal.

SOURCE: British Dental Journal 2003;194:453-455.