Trauma to floor of mouth

The patient visited the dentist for a lower molar crown preparation. During the course of the procedure, the rotating bur of the air turbine caught the floor of the mouth when the patient swallowed, causing a small laceration. The dentist, who was using a dental mirror to protect the tongue, informed the patient of the complication and recommended hot salt mouthwashes. The crown was fitted two weeks later when the floor of the mouth was noted to be healing well.

The patient returned to the surgery three months later complaining of a swelling in the floor of the mouth which was affecting her speech. On examination, the dentist noted saliva collecting in a pocket of tissue and referred the patient to the oral surgery department of the local hospital, where the swelling was opened and curretted. Two months later the patient was still having recurrent swelling and it was decided to excise the lesion and associated sublingual salivary gland, which was undertaken on a "day-stay" basis under general anaesthetic two months later. When reviewed one month post-operatively, it appeared the procedure had been successful and the patient was discharged.

Negligence alleged

The patient claimed the dentist had "dropped" the drill in her mouth and there were other differences in the account of events. The DDU's expert advised that an injury to the floor of the mouth caused in this fashion would be just the sort of triggering event that might cause a mucous retention cyst. The DDU'S expert also concluded that the technique of using a mouth mirror to retract the tissues of the floor of the mouth was a perfectly reasonable and orthodox method of securing safe access to prepare a full crown on a lower molar tooth and that the patient's account of the injury appeared unlikely. In his view the more likely explanation for the injury was that the patient swallowed, causing the tissues of the floor of the mouth to contact the bur, and that a laceration of the floor of the mouth caused in this way did not constitute a negligent act. The expert was quite certain that every dentist (himself included) had had many similar incidents even when full concentration and awareness was being applied to the task in hand.


The DDU senior claims handler discussed with the dentist the difficulty in successfully defending this type of injury, notwithstanding the supportive expert advice. In the DDU's experience, judges are unwilling to find that such an injury is simply a recognised and acceptable complication of tooth preparation. Furthermore, the patient would almost certainly have been able to secure an expert to contradict the DDU expert's view that the dentist was not negligent. There was also a conflict of evidence between the dentist and the patient as to the mechanism of injury and other factors concerning the management, such that the outcome of any litigation was uncertain.

With the dentist's agreement, the DDU negotiated a settlement of £6,000 without admission of liability.

This page was correct at publication on 04/04/2003. Any guidance is intended as general guidance for members only. If you are a member and need specific advice relating to your own circumstances, please contact one of our advisers.