According to Rood's criteria, what is the most likely sign of inferior alveolar nerve injury associated with third molar extraction?

The most indicative sign of inferior alveolar nerve injury following third molar extraction, according to Rood's criteria, is numbness in the lower lip. This symptom often arises because the inferior alveolar nerve, which is responsible for sensation in the lower lip and chin, can be damaged during the extraction of lower third molars, particularly when there is close anatomical proximity to the nerve.

The presence of numbness in the lower lip is a direct result of this nerve injury and is an important clinical finding to assess the extent of nerve damage. This numbness may be temporary or permanent, depending on the severity of the injury and the individual patient's healing capacity.

In contrast, signs such as darkening of the canal around the roots might represent other pathological findings or anatomical variations but do not specifically indicate nerve injury. Pain radiating to the ear can be a post-operative symptom, but it is more often associated with other types of complications, such as inflammation or referred pain, rather than direct nerve injury. Swelling in the submandibular area could indicate a range of complications including infection or hematoma formation, but it also does not specifically signify inferior alveolar nerve injury.

Thus, numbness in the lower lip stands out as the most specific and