Final answer:
An acute periapical abscess from a mandibular third molar tends to drain into the submandibular space due to its anatomical position relative to the infection site.
Step-by-step explanation:
An acute periapical abscess originating from a mandibular third molar generally points and drains into the submandibular space. The submandibular space is anatomically positioned to receive infections from the mandibular third molar due to its location below the mandible and because of the natural pathways of infection spread. The other listed options—pterygomandibular space, buccal vestibule, and buccal space—are less commonly involved in such instances.