Endodontics · patient case question
The horizontally impacted #17 contacts the distal root of #18, which shows a concave radiolucent defect at that point. What type of resorption is this?
Patient case: The Pimple That Comes and Goes
Patient: 52-year-old female
Chief Complaint: “There’s a pimple on my gum that comes and goes. It’s been almost two years.”
Background: Healthy, no medications. Describes intermittent swelling that drains, subsides for weeks, then recurs. Minimal pain throughout.
Medications: None
Vital Signs: BP 124/78 mmHg · HR 72 bpm · RR 16 · T 98.4°F
Findings: Tooth #14 has no restoration and has never received endodontic treatment. It gives no response to cold and is not tender to percussion. A well-defined periapical radiolucency is present, and a gutta-percha point placed in the sinus tract tracks radiographically to the apex of #14. Separately, tooth #29 has a fractured lingual cusp. Tooth #17 is horizontally impacted and its crown contacts the distal root of #18, which shows a concave radiolucent defect at the point of contact.
Show answer and explanation
Correct answer: B. External root resorption
- A. Incorrect. Replacement resorption is progressive substitution of root structure by bone following loss of periodontal ligament vitality, typically after avulsion or severe luxation. It causes ankylosis with loss of the ligament space and a high metallic percussion note.
- B. Correct. Sustained pressure from the impacted tooth stimulates clastic activity on the outer root surface. The defect originates externally at the point of contact, producing the concave saucer-shaped radiolucency described. The canal outline remains intact and traceable through the defect.
- C. Incorrect. Physiologic resorption is the normal process by which primary tooth roots are resorbed to permit exfoliation. It does not occur in permanent teeth.
- D. Incorrect. Internal resorption originates within the pulp space and expands outward, producing a balloon-like enlargement of the canal that is symmetrical and centered on the canal itself. The canal outline is lost at the site of the lesion.
Note: A useful radiographic discriminator: shift the horizontal angle and take a second view. An external defect moves relative to the canal; an internal lesion remains centered on the canal in both projections.