Endodontics · patient case question
The radiograph shows the post in tooth #9 is displaced and the tooth is mobile. What is the most appropriate treatment for tooth #9?
Patient case: Deciding whether two teeth can be saved
Patient: Female, 59 years old
Chief Complaint: “My dentist said one of these teeth has to come out but I want to keep them.”
Background: Both teeth were root-treated and posted more than ten years ago. No systemic disease.
Findings: A posterior tooth: previous root canal treatment, a persistent periapical radiolucency, a crown-to-root ratio of approximately 2:1, minimal remaining coronal tooth structure, and no opposing tooth in that position. Tooth #9: the post appears displaced on the radiograph and the tooth is mobile; tooth #8 also carries a post but is sound and immobile.
Show answer and explanation
Correct answer: C. Extraction
- A. Rebuilding both teeth ignores the fact that #9 is failing structurally, and it would subject a sound tooth (#8) to unnecessary intervention.
- B. Retreatment and crown lengthening address canal and margin problems. They cannot restore a root that has fractured or a post that has displaced through it.
- C. CORRECT. A DISPLACED post with tooth MOBILITY means the post has separated from the remaining root structure — in practice this indicates a vertical root fracture or catastrophic loss of the root. Neither is restorable, and EXTRACTION is the appropriate treatment, followed by a plan for replacement. Tooth #8, which is sound and immobile, is left alone and may serve as an abutment.
- D. Recementing treats a loose crown on a sound tooth. Here the failure is at the root, not the cement interface.