Sensory impairment following lower third molar surgery: a prospective study in New Zealand

This study reports the rate of impairment of inferior alveolar and lingual nerve sensation approximately 1 week after the removal of impacted lower third molars by 11 well-qualified oral and maxillofacial surgeons in New Zealand. The survey covered 2,178 patients who had 3,848 teeth removed; impairment was determined by direct questioning of the patients. After 7 days, the rate of inferior alveolar nerve impairment was 1.2 percent, and of lingual nerve impairment, 0.9 percent. The rate of inferior alveolar nerve impairment was significantly associated with age, occurring following removal of 0.2 percent of teeth in the age group 12-20 years, 1.3 percent in the group 21-30 years, 3.1 percent in the group 31-40 years, and 3.9 percent in the age group 41 years and over (P < 0.001). No impairment of the inferior alveolar nerve occurred when teeth were removed for orthodontic reasons, but impairment followed the removal of 1.6 percent of teeth when the reason for removal was infection, 0.8 percent when the teeth had been removed for prophylactic reasons, and 2.7 percent when the reason was other pathology. Age at the time of removal was not associated significantly with lingual nerve impairment (P = 0.98). Lingual nerve impairment occurred following the removal of 0.5 percent of teeth when the teeth had been removed for orthodontic reasons, 1.4 percent when the reason for removal was infection, 0.1 percent when the teeth had been removed for prophylactic reasons, and 0.5 percent when other pathology had been the reason for removal. All instances of impairment of the lingual nerve occurred when the nerve had been shielded. The results support a recommendation that impacted lower third molars be removed by age 20 years, and provide evidence against the advice to leave them until they give trouble, at least for patients under 30 years of age.