A patient habitually holds chewing tobacco in the labial/buccal vestibule of the mandible and develops an infection at the site. Given that the mandibular buccal alveolar bone is perforated ABOVE the attachment of the buccinator, into which space would infection most likely spread?

Correct answer: A. Buccal space

• A. Correct. The BUCCINATOR attachment on the mandible is the deciding landmark. If the infection perforates the buccal cortex ABOVE (superior to) the buccinator attachment, it drains into the vestibule and then into the BUCCAL SPACE, which lies between the buccinator medially and the skin/superficial fascia laterally. Clinically this gives cheek swelling that does not extend below the inferior border.
• B. Incorrect. The sublingual space is entered when a mandibular infection perforates the LINGUAL plate ABOVE the mylohyoid line — typically from premolars and the first molar.
• C. Incorrect. The retropharyngeal space is a deep secondary space reached only by extension from the lateral pharyngeal space — it is not a primary space for a vestibular infection.
• D. Incorrect. The submandibular space is entered when a mandibular infection perforates the LINGUAL plate BELOW the mylohyoid line — typically from second and third molars, whose apices lie below that line.

Note: Two-question rule for mandibular spread: (1) buccal or lingual plate? (2) above or below the muscle attachment (buccinator buccally, mylohyoid lingually)? Above buccinator → vestibule/buccal space; below → buccal space proper. Above mylohyoid → sublingual; below → submandibular.