Ceramic Crown Delivery

Correct answer: D. 20–60 seconds

• A. Five seconds is insufficient to create the retentive etch pattern.
• B. Ten minutes would severely degrade the restoration.
• C. Three minutes over-etches lithium disilicate and weakens the ceramic surface.
• D. Correct. Lithium disilicate is etched with roughly 5% hydrofluoric acid for about 20 seconds — the recall answer here is 60 seconds — which selectively dissolves the glassy matrix and creates micromechanical retention before silanation.

Note: Etching time is ceramic-specific: about 20 s for lithium disilicate, 60–120 s for feldspathic porcelain. Zirconia is not etched with HF at all — it is air-abraded and treated with an MDP primer.

Correct answer: D. Resin cement

• A. Zinc oxide-eugenol is a provisional cement, and eugenol inhibits resin polymerization.
• B. Zinc phosphate has no adhesive bond to ceramic and would leave the restoration mechanically unsupported.
• C. Glass ionomer is acceptable for zirconia and metal but does not develop the bond that glass-ceramics require.
• D. Correct. Lithium disilicate is adhesively cemented with resin cement after HF etching and silane coupling. The resin bond reinforces the ceramic and substantially raises fracture resistance.

Correct answer: C. Exposure of the underlying metal or dentin at the margin from wear and recession

• A. Tetracycline staining is generalized and banded through the whole tooth, present from development — it does not appear as a new marginal line.
• B. Fluorosis produces white opaque or mottled brown enamel, developmentally, not a marginal grey line.
• C. Correct. Parafunction plus gingival recession exposes the metal collar of a ceramo-metal crown or the darker underlying dentin, producing a grey line at the margin.
• D. An amalgam tattoo is a blue-grey macule in the soft tissue, not a discoloration of the crown margin.

Correct answer: A. Heat-cured acrylic

• A. Correct. Heat-curing yields a higher degree of conversion, less residual monomer, and lower porosity, so there is less surface area and fewer micropores for Candida to colonize.
• B. Light-cured repair materials are typically more porous than a processed heat-cured base.
• C. Self-cured acrylic has higher residual monomer and greater porosity, favoring colonization.
• D. Chairside relines are among the most porous and are notorious for candidal colonization.

Correct answer: B. Antifungal therapy — fluconazole or nystatin — combined with denture hygiene and nighttime removal

• A. The lesion is diagnosed clinically by its conformity to the denture outline; biopsy is unnecessary.
• B. Correct. This is denture stomatitis — chronic atrophic candidiasis. Treatment combines an antifungal with disinfection of the prosthesis and removal at night, since the fitting surface is the reservoir.
• C. A new denture placed into an untreated infected mouth will simply be recolonized.
• D. Antibacterial therapy has no effect on a fungal infection and may worsen it.