An infection from a mandibular second molar spreads beyond the bone. Which fascial space is involved FIRST?

Correct answer: D. Submandibular space

• A. ❌ The pterygomandibular space is usually involved secondarily, or iatrogenically after an inferior alveolar block.
• B. ❌ The sublingual space is entered by teeth whose apices sit ABOVE the mylohyoid line — the premolars and first molar.
• C. ❌ The buccal space is involved when infection perforates the buccal plate, more typical of maxillary molars and some mandibular molars.
• D. ✅ CORRECT — The apices of the mandibular SECOND and THIRD molars lie BELOW the mylohyoid line, so perforation of the lingual plate drains beneath the mylohyoid muscle into the SUBMANDIBULAR space.

Note: Mylohyoid line is the divider: apices above it → sublingual; apices below it → submandibular. Ludwig angina = bilateral submandibular + sublingual + submental.