Prosthodontics & Occlusion · patient case question
For the repeatedly debonding crown on #8, which intervention is NOT required?
Patient case: Crown that repeatedly debonds, and a new crown that will not seat
Patient: Female, 32 years old
Chief Complaint: “The crown on my front tooth keeps coming off, and it does not look right.”
Background: Crown on tooth #8 recemented three times in two years. No systemic disease. No reported grinding.
Vital Signs: BP 116/72 mmHg · HR 70 bpm
Findings: DEEP anterior overbite with heavy contact on the lingual surface of #8 in centric and on protrusive excursion. The abutment preparation is adequate in height and taper. Periodontium healthy: 2 mm probing depths, 4 mm of attached gingiva, no recession. At try-in of a replacement crown for #9, the restoration will not seat fully and a visible open margin remains, though the internal surface shows no interference on inspection.
Show answer and explanation
Correct answer: B. A free gingival graft
- A. Reviewing the preparation for resistance form is always part of investigating a debonding restoration, even when it looks adequate — short or over-tapered preparations are the other common cause.
- B. CORRECT as the answer — a FREE GINGIVAL GRAFT is not needed. It is indicated where attached gingiva is INADEQUATE or recession is progressing. This patient has 2 mm probing depths, 4 mm of attached gingiva and no recession. The periodontium is healthy and is not the problem.
- C. Occlusal analysis is exactly what IS needed. A deep overbite loading the lingual surface of a maxillary central in centric and protrusion applies a repeated horizontal dislodging force to the crown — the cement fatigues under shear and the restoration debonds. Adjusting or redistributing that guidance is the definitive fix.
- D. Mounted diagnostic casts let the anterior guidance be evaluated and modified on the articulator before anything irreversible is done in the mouth. In a repeatedly failing anterior restoration this is standard.
Note: When a restoration fails repeatedly, the question is never 'which cement next'. It is WHY. The three causes in order of frequency: inadequate retention and resistance form, occlusal overload or an unfavourable guidance, and a compromised margin or contaminated cementation field.
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