MDDUS CASE STUDY: Permanent nerve injury

It is alleged that the dentist did not tell the patient about the clinical risks associated with incising an abscess...

12 February, 2019 / management
 Aubrey Craig  


Mr T attends his dental surgery complaining of pain in his lower left canine tooth. The dentist – Mr R – notes a sinus draining from the apex of the tooth. A radiograph shows a periapical radiolucency and the tooth is non-responsive to cold stimulus. Mr R discusses the treatment options with the patient who decides on a course of root canal therapy. Mr R removes the non-vital pulpal tissue, irrigates the root canal, dries it and dresses it appropriately and asks the patient to make a longer appointment for root canal treatment (RCT).

DAY 30

The treatment on LL3 is completed without complications. The patient is advised to return to the surgery if he experiences any pain or swelling.

DAY 33

Mr T attends the surgery with pain and numbness in the LL region with swelling spreading under the tongue and difficulty swallowing. An abscess is noted at LL3 and Mr R advises that it should be incised.

Mr T agrees and the dentist administers a local anaesthetic by way of an inferior nerve block, not injecting into the swelling, and proceeds to incise the abscess with a scalpel, releasing copious pus. The patient is given a prescription for an antibiotic (amoxicillin).

DAY 40

The patient telephones the surgery to say that he is still suffering numbness in the lower left lip and some swelling. The dentist advises Mr T that paraesthesia is not uncommon and should resolve within two weeks, along with the swelling.


Mr T returns to the surgery still complaining of numbness in his lip and is seen by the dentist who says it may take up to a few months more for sensation to return to normal. The dentist makes a note in the record to consider removal of the root canal treatment if the numbness has not resolved or to discuss onward referral to an endodontic specialist or dental hospital.

More than a year later the dentist receives a letter of claim for damages in regard to his treatment of Mr T. It is alleged that the dentist did not tell the patient about the clinical risks associated with incising the abscess at LL3 and thus consent was not informed. Nor were the risks discussed for local anaesthesia involving nerve block injections. Mr T has stated that had he known of the attendant risks he would not have agreed to
the procedure.

In regard to the incision it is alleged that the dentist failed to take into account the anatomical course of the mental nerve and during treatment cut it or some of its fibres. The letter also claims a breach of duty of care for failing to refer Mr T to an expert maxillofacial surgeon for drainage of the abscess and later when it became clear that the paraesthesia was not resolving.

The letter states that due to the dentist’s negligent treatment the patient is now left with permanent loss of sensation, requiring referral to a dental neurological specialist for further treatment.

MDDUS advisers assess the associated case papers and commission a report from an expert in oral and maxillofacial surgery. In the expert’s opinion, the nerve injury is permanent given the period of time now passed without significant improvement.

Four theoretical causes of the injury are considered in the report. The expert rules out injury during the root canal treatment because of the position of the mental nerve relative to the apex of the canine tooth. He also believes it is unlikely that the local anaesthetic injection prior to the RCT could have led to the nerve injury. Infection could have also caused altered sensation but again the position of the nerve relative to the tooth makes this unlikely.

The expert expresses the opinion that the paraesthesia most likely resulted from branches of the mental nerve being cut when the dentist was incising the abscess, but such a complication would not in itself be negligent.

He states that it is easy to damage these nerves as they lie just below this mucosa in the buccal sulcus. He also notes that the patient is clear in his evidence that the change in character and perception of
the sensation was quite distinct after
the incision.

The crucial issue is the lack of any evidence in the patient records that the risks of the procedure were discussed.

Key points

  • Ensure that relevant risks in any procedure are discussed with patients.
  • Discussions with patients in regard to consent should be recorded routinely in the notes.

Aubrey Craig is head of dental division at MDDUS

Tags: 2019 / MDDUS / permanent nerve injury

Categories: Magazine / Management

Comments are closed here.

Scottish Dental magazine