What area will anesthesia placed 1 mm above the last lower molars anesthetize?

The placement of anesthesia 1 mm above the last lower molars primarily targets the long buccal nerve. This nerve provides sensory innervation to the buccal mucosa and skin over the mandible in the posterior region, specifically around the area of the lower molars. Therefore, when anesthesia is administered in this position, it effectively numbs sensations in the cheek area adjacent to the last molars, which is precisely the role of the long buccal nerve.

The other anatomical structures mentioned do not receive anesthesia from this specific injection site. For instance, the lingual nerve innervates the anterior two-thirds of the tongue and the lingual mucosa but is located more medially; the inferior alveolar nerve runs deeper and would require injection near the mandibular foramen to achieve profound mandibular anesthesia; and the maxillary sinus is not affected by a mandibular injection, as it requires an approach along the maxilla. Thus, the most appropriate choice regarding the site of anesthesia administration above the last lower molars is the long buccal nerve.