Where should the external finish line of the mandible be located?

Where should the external finish line of the mandible be located?

• A. Continuous from the guide plate
• B. 2 mm labial to the lower teeth
• C. On the inferior border of the mandible
• D. At the buccal vestibule

Answer: (A)

Positioning the external finish line to run continuously from the guide plate ensures a single, smooth border that follows the planned path of insertion and retention for the mandibular RPD. The guide plate defines where the border should terminate, so keeping the finish line continuous with it prevents abrupt contour changes that could irritate tissues, affect seating, or disrupt the intended border path. If the finish line were placed away from the guide plate—such as labially to the teeth, along the inferior border, or right at the buccal vestibule without reference to the plate—the border could become irregular, unstable, or misaligned with the rest of the denture, compromising fit and comfort.

Positioning the external finish line to run continuously from the guide plate ensures a single, smooth border that follows the planned path of insertion and retention for the mandibular RPD. The guide plate defines where the border should terminate, so keeping the finish line continuous with it prevents abrupt contour changes that could irritate tissues, affect seating, or disrupt the intended border path. If the finish line were placed away from the guide plate—such as labially to the teeth, along the inferior border, or right at the buccal vestibule without reference to the plate—the border could become irregular, unstable, or misaligned with the rest of the denture, compromising fit and comfort.