Pathology · patient case question
Which of the following cells is directly responsible for this defect?
Patient case: Radiographic root defect on routine imaging
Patient: Adult patient
Chief complaint: No symptoms reported. Finding noted incidentally on routine radiographs.
History: No history of trauma to the area recalled. No orthodontic treatment.
Findings: Sagittal and cross-sectional CBCT slices show a concave, scooped-out defect on the root surface with loss of the adjacent lamina dura. The overlying crown is intact.
Show answer and explanation
Correct answer: B. Odontoclasts
- A. Osteoblasts FORM bone and are the cells that later deposit bone into a resorbed root during ankylosis and replacement resorption.
- B. CORRECT. ODONTOCLASTS are the multinucleated cells that resorb DENTAL hard tissue — cementum, dentin and, rarely, enamel. They are functionally and morphologically near-identical to osteoclasts, arising from the same monocyte-macrophage lineage and using the same ruffled border, hydrogen-ion pump and cathepsin K machinery. The name simply reflects the substrate: when the tissue being resorbed is TOOTH, the cell is called an odontoclast.
- C. Odontoblasts FORM dentin. They line the pulp and lay down primary, secondary and tertiary dentin — they are constructive, not destructive.
- D. Osteoclasts resorb BONE. They are involved in the surrounding alveolar changes and in replacement resorption, but the defect described here is in the root surface itself.
Note: Distinguish the two directions this can take. EXTERNAL resorption begins on the root surface and is driven by damage to the protective cementoblast/precementum layer — from trauma, replantation, orthodontic force, chronic periapical inflammation or an adjacent impacted tooth. INTERNAL resorption begins in the canal, requires vital inflamed pulp tissue, and is arrested by root canal treatment.