Invasion of Calcium Hydroxide Preparations Leading to Severe Chemical Nerve Injury Treated Through Nerve Repair Using Artificial Nerve Conduit: A Case Report

Calcium hydroxide is an effective agent in endodontic treatment worldwide. Some cases reported that treating a mandibular molar can lead to severe incidents of overfilling from the root canal, which leads to nerve disturbance. However, it remains unclear how nerve disturbance affects the degree of the recovery of sensation, whether through treatment or observation. We present a nerve repair of the inferior alveolar nerve injury caused by endodontic treatment, wherein perception did not improve after several months of observation. Postoperative pathological findings revealed that the injured nerve bundle contained calcium hydroxide and colloidal foreign bodies as a residue of barium sulfate. Therefore, sensory malfunction in our case was attributed to two factors: chemical damage due to the strong alkalinity and radiopacity of barium sulfate residue in the ingredients of calcium hydroxide and physical damage from the medication. This incident highlights the necessity for dentists to carefully handle the injection type of chemical agents for endodontic treatment or consider indirect application in the root canal. Furthermore, in the absence of recovery of sensory function, nerve repair through an artificial nerve conduit using an appropriate nerve agent should be considered to relieve pressure on the nerve. In this case of chemical injury to the inferior alveolar nerve treated with nerve repair, the nerve recovery was assessed as Grade S3 on the British Medical Research Council scale 6 months postoperatively; additionally, the nerve regained functional sensory recovery from this grade.