Prosthetics Design & Fabrication Flashcards

The primary reason for using a vacuum during porcelain firing in PFM and all-ceramic restorations is:

Answer: To eliminate air bubbles, reduce porosity, and improve ceramic density

Firing under vacuum removes trapped air from the ceramic mass, producing a denser, stronger, and more translucent restoration with fewer surface defects.

When designing the gingival embrasure space of a posterior FPD, the ceramist should create an embrasure that:

Answer: Allows access for interdental cleaning aids while maintaining natural soft-tissue health

An open, cleanable gingival embrasure allows floss or interproximal brushes to access the connector/pontic area, reducing plaque accumulation and perio risk.

Which parameter of an articulator is adjusted to simulate the lateral condylar guidance (Bennett angle) during prosthetic fabrication?

Answer: Lateral condylar inclination (side shift) setting on the articulator

The Bennett angle adjustment on a semi-adjustable articulator programs the immediate side shift and progressive side shift of the working condyle during lateral excursion.

A ceramist is fabricating a high-strength zirconia coping for a molar crown. Which surface treatment BEST promotes adhesion of the veneering porcelain to the sintered zirconia?

Answer: Airborne particle abrasion with 50 µm alumina and application of a zirconia-specific liner

Alumina particle abrasion creates surface roughness, and a manufacturer-approved zirconia liner promotes chemical and micromechanical bonding of veneering ceramic.

When a dental ceramist encounters a 'localized chipping' of the veneering ceramic on a finished PFM crown, the BEST corrective step before delivery is:

Answer: Remove loose ceramic, repair with compatible porcelain, re-fire, and re-glaze the restoration

Repairing with compatible porcelain and re-firing ensures structural integrity and accurate shade match before the restoration is delivered to the patient.

The concept of 'biologic width' is critical in prosthetic design because violating it by placing a crown margin too deep subgingivally can result in:

Answer: Chronic inflammation, bone loss, and periodontal breakdown

Encroaching on the connective tissue and junctional epithelium attachment (biologic width ~2 mm) triggers inflammatory bone resorption to re-establish that space.

Which type of dental stone (gypsum product) is MOST appropriate for fabricating a highly accurate die for crown and bridge prosthetics?

Answer: Type IV or Type V high-strength, low-expansion die stone

Type IV and V die stones have the highest strength and lowest expansion, producing the most dimensionally accurate dies for precision crown and bridge fabrication.