Risk factors associated with injury to the inferior alveolar and lingual nerves following third molar surgery—revisited

doi:10.1016/j.tripleo.2009.10.010

Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology

Volume 109, Issue 3, March 2010, Pages 335-345

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https://doi.org/10.1016/j.tripleo.2009.10.010 Get rights and content

Objective

Earlier reports, including a preliminary study within our unit, have shown that the surgeon's experience is one of the most influential factors in determining the likelihood of both permanent inferior alveolar nerve (IAN) and lingual nerve (LN) paresthesia, following third molar surgery. The effect of this and other factors influencing such prevalence are assessed in this study.

Study design

This prospective study involved 3236 patients who underwent surgical removal of impacted third molars. Patients' demographics and radiological parameters were recorded along with the grade of the treating surgeon. The prevalence of inferior alveolar and lingual nerves paresthesia at 1 month, 6 months, and 18 to 24 months postoperatively were also traced.

Results

At 1 month postoperatively, the incidence of IAN paresthesia was 1.5% and the LN was 1.8%. These figures decreased over time and 18 to 24 months postoperatively, the incidence of permanent dysfunction of the IAN was 0.6% and LN was 1.1%. With regard to inferior alveolar nerve paresthesia, risk factors included the patient's age (26-30 years), horizontally impacted teeth, close radiographic proximity to the inferior alveolar canal (IAC), and treatment by trainee surgeons. With regard to the lingual nerve, risk factors included male patients, distoangular impactions, close radiographic proximity to the IAC, and treatment by trainee surgeons.

Conclusion

One of the main risk factors of developing permanent sensory dysfunction in the distribution of these nerves is related to the surgical skills/experience of the operator. Other factors are associated with the type of impaction and the radiographic proximity of the tooth to the inferior alveolar nerve. Such long-term complications can affect the patient's quality of life; the impact on profession, education, and research is unknown.

Section snippets

Materials and Methods

This prospective study involved 3236 patients who underwent surgical removal of impacted lower third molars from 1998 to 2006. Patients' demographics were recorded along with the radiological characteristics for each case. The patients were randomized into 2 groups using a computer format.

Patients included in the study had their third molars removed surgically at the University College Hospital, London. The study protocol was approved by the Joint University College London/University College

Results

The 3236 patients treated had a mean age of 24.2 years. The age of the patients in this study ranged from 17 to 36 years. The 21- to 25-year age group had the largest number of patients (1594/3236, 49.2%). There was a slight predominance of female patients in this study (1791/3236, 55.3%). Most of the teeth were partially impacted (2572/3236, 79.5%) with either vertical (1128/3236, 34.9%) or mesial (1518/3236, 46.9%) spatial relationship. Over three quarters (2531/3236, 78.2%) of the teeth were

Discussion

In 1951, Sunderland²⁰ proposed a classification of nerve injuries. It is based on the theory that the degree of sensory disturbance and subsequent recovery following nerve injury depend on the severity of the insult. The classification involved neuropraxia, axonotmesis, rupture of endoneurium or perineurium, neurotmesis, and perineural inflammation.

Conclusions

The findings of this study are similar to the preliminary study¹⁹ and to other studies, with permanent sensory loss of the inferior alveolar and lingual nerves to be 0.6% and 1.1%, respectively. Although these figures are relatively low, they are still of great significance for both patients and clinicians and may have legal implications. All patients must be warned of the risks of third molar surgery, including possible damage to the inferior alveolar and lingual nerves and informed consent