A cone-beam CT of a tooth shows a well-defined radiolucent defect within the root canal / root structure consistent with internal root resorption. Which of the following cells is directly responsible for the resorption of the dental hard tissue?

Correct answer: D. Odontoclasts

• A. Odontoblasts form dentin — they are secretory, not resorptive.
• B. Osteoclasts resorb bone. While they share a common precursor with odontoclasts (monocyte-macrophage lineage) and are histologically similar, resorption of dental hard tissue (dentin, cementum) is attributed to odontoclasts.
• C. Osteoblasts synthesize new bone matrix; they are not resorptive cells.
• D. CORRECT — Odontoclasts are multinucleated giant cells derived from the monocyte-macrophage lineage that resorb dental hard tissues (dentin and cementum). They are the cells responsible for physiologic resorption of primary teeth and pathologic internal/external root resorption.