Prosthodontics & Occlusion · patient case with 4 questions
Failing anterior crown in a bruxer
Patient: 49-year-old woman.
Chief complaint: My crown feels loose and it does not match my other teeth.
History: Crown placed approximately twelve years ago. Partner reports night-time grinding.
Findings: Porcelain-fused-to-metal crown on a maxillary anterior tooth with a visible metal collar at the margin and gingival recession. The crown is markedly brighter and whiter than the adjacent teeth, which are distinctly yellow. Generalized wear facets on the posterior teeth. The crown moves on digital pressure.
Question 1
What is the MOST appropriate treatment?
Show answer and explanation
Correct answer: B. Remove the crown, assess the abutment, and fabricate a new crown
- A. Veneering composite over a metal collar is a cosmetic patch that leaves the loose fit and the caries risk untouched.
- B. CORRECT. The restoration has failed on three counts — it is loose, the margin is exposed, and the shade is wrong. A loose crown almost always has caries beneath it. Remove it, evaluate the abutment, and remake.
- C. Ceramic and metal do not respond to bleaching agents; only natural tooth structure does.
- D. Recementing preserves every problem the patient came in with and seals bacteria against a possibly carious abutment.
Question 2
Given the wear facets and the esthetic demand, which material is MOST appropriate for the replacement?
Show answer and explanation
Correct answer: D. Monolithic zirconia
- A. A thin feldspathic veneer will not survive parafunction and does not replace a full-coverage restoration.
- B. Gold has excellent mechanical properties but is unacceptable esthetically on an anterior tooth.
- C. Repeating the metal-collar design reproduces exactly the complaint that brought her in.
- D. CORRECT. Monolithic zirconia gives high flexural strength for a parafunctional patient with no metal substructure, so there is no dark cervical line now or after further recession. Lithium disilicate has the edge esthetically where translucency matters most, but strength is the governing concern in a bruxer.
Question 3
The crown reads as too bright and chalky beside her yellow natural teeth. Which dimension of colour is mismatched?
Show answer and explanation
Correct answer: D. Value
- A. Hue is the basic colour family — the A, B, C, D letters on the Vita guide. A hue error looks like the wrong colour family, not excessive brightness.
- B. Chroma is saturation, the 1 to 4 number. Low chroma contributes to a washed-out look but is not the dominant descriptor here.
- C. Translucency affects depth and vitality of appearance but is not the primary error described.
- D. CORRECT. VALUE is lightness versus darkness — the amount of grey. It is the dimension the eye registers first, which is why a crown that is 'too white' leaps out. Squinting suppresses colour perception and isolates value, which is why clinicians squint when matching shades.
Question 4
What additional protective measure should be part of the plan?
Show answer and explanation
Correct answer: B. An occlusal night guard
- A. Opening the vertical dimension across the whole mouth is a major irreversible undertaking, not a protective adjunct for a single crown.
- B. CORRECT. A hard occlusal splint distributes parafunctional load and protects both the new ceramic restoration and the remaining dentition. Without it, the replacement is exposed to the same forces that contributed to the first failure.
- C. Muscle relaxants have a limited, short-term role in acute myofascial pain and do not protect the restoration.
- D. Placing new ceramic in an unprotected bruxing occlusion invites the same outcome again.
Practice patient cases Prosthodontics & Occlusion study notes