Panoramic radiographic findings as predictors of inferior alveolar nerve exposure following third molar extraction

The aim of this study was to estimate the sensitivity and specificity of panoramic radiographic findings in relation to inferior alveolar nerve (IAN) exposure after mandibular third molar (M3) extraction.

The study used a retrospective cohort model. The primary predictor variable was the presence or absence of > or = 1 panoramic radiographic sign associated with an increased risk for IAN injury. The secondary predictor variable was the surgeons assessment of IAN exposure risk. The outcome variable was IAN exposure, defined as direct visualization of the IAN at the time of M3 extraction. Appropriate univariate and bivariate statistics were computed and the level of statistical significance was set at P < or = .05.

The sample was composed of 230 patients having 423 mandibular M3s evaluated and removed. Following M3 extraction, the IAN was visualized in 24 (5.7%) extraction sites. Four of the radiographic signs were statistically associated with IAN exposure ( P < or = .05). The sensitivities and specificities of the 4 radiographic findings ranged from 0.42 to 0.75 and 0.66 to 0.91. The clinicians preoperative estimate of the likelihood of IAN exposure was statistically associated with IAN exposure after M3 extraction ( P < .001; sensitivity = 0.79; specificity = 0.86).

Four radiographic findings (darkening of the tooth root, narrowing of the tooth root, interruption of the white lines, and diversion of the canal) were statistically associated with IAN exposure following M3 extraction. The surgeons overall estimate of risk based on the panoramic radiograph was also statistically associated with an increased risk of IAN exposure.