How does the mandible increase in length during growth?

Correct answer: B. Apposition of bone at the posterior border of the ramus with resorption at the anterior border

• A. ❌ Apposition at both borders would thicken the ramus rather than relocate it.
• B. ✅ CORRECT — The ramus relocates POSTERIORLY by depositing bone on its posterior border while resorbing bone from its anterior border. This lengthens the mandibular body and creates the space into which the permanent molars erupt. The condyle contributes vertical/ramus height growth by endochondral ossification.
• C. ❌ This is reversed — anterior apposition with posterior resorption would shorten the body and eliminate molar space.
• D. ❌ The mandibular symphysis fuses in the first year of life and is not a growth site thereafter.

Note: The concept is 'relocation by remodeling' (Enlow). Mandible = endochondral at the condyle + surface remodeling of the ramus. Maxilla = sutural growth + surface remodeling, displaced downward and forward.