Incidence of neurosensory deficits and recovery after lower third molar surgery: a prospective clinical study of 4338 cases

Abstract

A prospective study of all lower third molar surgery performed in the outpatient extraction clinic of a teaching dental hospital was conducted from January 1998 through October 2005 to determine the incidence of subsequent neurosensory deficit due to inferior alveolar nerve (IAN) and lingual nerve (LN) injury, to examine possible contributing risk factors and to describe the pattern of recovery. 3595 patients were included (61% female, 39% male; age range, 14-82 years). Of the 4338 lower third molar extractions performed by various grades of operators, 0.35% developed IAN deficit and 0.69% developed LN deficit. Distoangular impaction was found to increase the risk of LN deficit significantly (p<0.001). Depth of impaction was related to the risk of IAN deficit (p<0.001). Undergraduates caused more LN deficits (p<0.001). Sex, age, raising of a lingual flap, protection of LN with a retractor, removal of distolingual cortex, tooth sectioning and difficulty in tooth elevation were not significantly related to IAN or LN injury. Postoperative recovery from IAN and LN deficits was noted most significantly at 3 and 6 months, respectively. By the end of the follow-up period, 67% of IAN deficits and 72% of LN deficits had recovered completely.

Mandibular Third Molar Impaction: Review of Literature and a Proposal of a Classification

“…Incidences of inferior alveolar nerve injury in fully erupted, partially erupted and unerupted lower wisdom teeth were 0.3%, 0.7% and 3.0%, respectively [65,66]. The risk of nerve injury is increasing with the depth of the impacted mandibular wisdom teeth [23,66].…”

“…It was demonstrated the relationship between pattern of impaction and inferior alveolar nerve injury. The incidence of nerve injury was highest in horizontally impacted lower wisdom teeth (1.7%), followed by distal impaction (1.4%), mesial impaction (1.3%) and vertical impaction (1.1%) [23,65,66]. …”

“…Surgery on unerupted mandibular third molars was at higher risk (5.8%) of lingual nerve injury compared with erupted (0.3%) or partially erupted (2.0%) teeth (P < 0.0001) [66,73]. The incidence of lingual nerve injury was highest in distally impacted lower wisdom teeth (4.0%, P < 0.01), followed by horizontal impaction (2.8%), mesial impaction (2.4%) and vertical impaction (1.9%) [23,46,66].…”

“…Surgery on unerupted mandibular third molars was at higher risk (5.8%) of lingual nerve injury compared with erupted (0.3%) or partially erupted (2.0%) teeth (P < 0.0001) [66,73]. The incidence of lingual nerve injury was highest in distally impacted lower wisdom teeth (4.0%, P < 0.01), followed by horizontal impaction (2.8%), mesial impaction (2.4%) and vertical impaction (1.9%) [23,46,66]. The risk ratio of lingual nerve injury was 1.94 times more likely to occur if the lingual flap was raised than if it was not and 4.1 times more likely to occur if the lingual split technique was used in comparison with the buccal approach [72].…”

“…It was discussed previously that iatrogenic injury to the lingual nerve may happen during third molar surgery due to the anatomical proximity of the cortex region of the molar to the nerve [52]. Surgery on unerupted mandibular third molars was at higher risk (5.8%) of lingual nerve injury compared with erupted (0.3%) or partially erupted (2.0%) teeth (P < 0.0001) [66,73]. Thus the highest risk of lingual nerve injury was scored in case when the tooth is partially impacted or completely encased in the bone (A2 or A3) and is located closer to the lingual wall.…”