Gerald S. Fine, D.D.S.
Oral and Maxillofacial Surgery
Last week the dental assistant of a neighboring general dentist asked me to examine her for limitation of opening and numbness involving the mandibular posterior area. She had been treated the previous afternoon by the general dentist she works for and he placed an occlusal restoration on the mandibular right first molar tooth. The assistant had informed the dentist that she sometimes requires additional anesthesia as well as that she was "sensitive" to epinephrine. He ignored her comments about epinephrine sensitivity, but responded to her comment about often times requiring additional anesthesia by repeated multiple injections to the mandibular right inferior alveolar area administering Xylocaine 2% with epinephrine 1:100,000. The assistant developed limitation of opening, and lingual anesthesia which was of grave concern to her the next morning. To complicate matters, the general dentist was unavailable to see her and the message on his answering machine referred all patients with dental emergencies to their neighborhood hospital. This provided additional patient anxiety.
Nerve damage may occur as a complication of the local anesthesia itself. Cases reporting altered sensation in the distribution of the inferior alveolar or lingual nerves after injection of a local anesthesia for restorative treatment are not uncommon.
One study reviewed identified patients undergoing restorative dental treatment who developed nerve damage (even when no surgical procedure is performed). In almost two out of three instances nerve damage developed after a single injection to the inferior alveolar region was administered. The remainder of the patients had two or more injections administered. The anesthetic agents administered included: Lidocaine 2%; and Mepivicaine 2% with levonordefrin 1:20,000. Several of the patients reported that they experienced an electric shock type sensation with the injection. The remaining patients reported no such phenomenon. Nerve damage occurred in most cases to the lingual nerve and to a lessor extent to the inferior alveolar nerve. One third of the patients had full recovery with in one year of the occurrence. The remaining patients still demonstrated residual nerve damage 18 months later.
The incidence of nerve damage is estimated to be 1 in 750,000, although this probably an underestimation. No one type of local anesthesia is more likely to cause damage, not is the number of injections at one site or at one visit significantly related to nerve damage. Direct trauma from the needle is probably not responsible for the nerve damage. Other possible causes include intraneural hematoma formation or local anesthetic toxicity. When nerve damage is still present three weeks after injection, the incidence of complete recovery is low.
I examined the dental assistant and a diagnosis of hematoma at the injection site was made. The patient was placed on Motrin and she was asked to apply warm moist packs to the area. The dental assistant was seen three days later to follow up examination and she demonstrated a complete recovery. In this instance recovery was total and uneventful.
Gerald S. Fine, D.D.S.
Practice limited to oral & maxillofacial surgery