Restorative & Materials · patient case question
For the posterior tooth, which of the following is NOT a reason to extract it?
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: A. Absence of an opposing tooth
- A. CORRECT as the exception. Having NO ANTAGONIST is not by itself a reason to remove a tooth. An unopposed tooth may over-erupt, and that is managed with monitoring, an opposing restoration, enameloplasty or orthodontic intrusion. Extracting a sound tooth because nothing bites against it is not justified — the tooth may also become an abutment later.
- B. A crown-to-root ratio of 2:1 is severely unfavourable. The ideal is 1:2 and the minimum acceptable is roughly 1:1. At 2:1 the lever arm above the bone overwhelms the support below it.
- C. Without enough sound tooth structure to give a ferrule of 1.5 to 2 mm, a crown will fail no matter how well the post is placed. This is a legitimate extraction criterion.
- D. A periapical radiolucency that persists after root canal treatment signals failure. If retreatment or apical surgery is not feasible, extraction follows.
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