Restorative & Materials · single question
For a patient with a fractured mandibular molar with limited remaining tooth structure and bruxism, which crown material is best?
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Correct answer: D. Zirconia
For a posterior tooth with limited structure and a patient with bruxism (parafunctional habits), ZIRCONIA is the material of choice. Zirconia has exceptional strength (flexural strength 900-1200 MPa), fracture toughness superior to PFM, and no porcelain overlay to chip in monolithic designs. PFM has a porcelain veneer that fractures under bruxing forces. Full porcelain (feldspathic) is too brittle for bruxers. Stainless steel crowns are used primarily in pediatric dentistry.
- A. INCORRECT. Full porcelain crowns (feldspathic porcelain) have excellent esthetics but poor fracture resistance under heavy occlusal load from bruxism. Not appropriate for posterior bruxers with limited tooth structure.
- B. INCORRECT. Stainless steel crowns (SSCs) are primarily used for primary teeth in pediatric dentistry. They are not appropriate for adult posterior restorations.
- C. INCORRECT. Porcelain-fused-to-metal (PFM) crowns have a porcelain veneer that is susceptible to CHIPPING and fracture under bruxing forces. The metal substructure is strong, but the porcelain overlay is a weak point in parafunctional habits.
- D. CORRECT. Monolithic zirconia is the material of choice for posterior crowns in bruxers. It has extremely high strength and fracture toughness, no porcelain overlay to chip, and performs well under heavy occlusal forces.
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