Laboratory Techniques & Technology Flashcards

Which characteristic of a porcelain furnace most directly affects the reproducibility of ceramic color between firings?

Answer: Thermocouple calibration accuracy

An accurately calibrated thermocouple ensures the actual muffle temperature matches the set temperature, which is critical for consistent ceramic maturation and shade.

A ceramist is building a layered ceramic crown and notices the dentin porcelain slumping during firing. The MOST likely cause is:

Answer: Porcelain mixed with too much modeling liquid (over-wet)

Excess liquid in the porcelain mix reduces surface tension during firing, causing the ceramic mass to slump and lose anatomical form.

In digital dentistry, an intraoral scanner exports data in which standard file format that dental CAD software reads?

Answer: .STL or .PLY

STL (Standard Tessellation Language) and PLY are the standard mesh file formats used to transfer three-dimensional scan data between digital dentistry devices and software.

What is the purpose of applying multiple thin layers of opaque porcelain rather than one thick layer over a metal framework?

Answer: To achieve better opacity with fewer internal bubbles and stronger bond

Thin opaque layers fire more completely, minimize trapped air voids, and create a stronger oxide-to-ceramic interface than a single thick application.

Which clinical situation requires a ceramist to fabricate a restoration with a subgingival margin rather than a supragingival margin?

Answer: When esthetics demand concealing the crown margin below the gingival tissue

Subgingival margins are placed when esthetic requirements demand that the crown-tooth junction be hidden by gingival tissue, particularly in the esthetic zone.

A 3D-printed resin temporary crown must be polished with which type of abrasive sequence to achieve a smooth, biocompatible surface?

Answer: Progressive grits from coarse to fine followed by a high-luster polish

Sequential polishing from coarser to finer abrasives progressively removes surface irregularities, and a final high-luster step seals the surface to reduce plaque adhesion.

When designing an all-ceramic anterior bridge using CAD software, what minimum connector cross-sectional area is generally recommended to prevent fracture?

Answer: 4 mm² for zirconia; 2 mm² for lithium disilicate

Zirconia's high flexural strength allows smaller connectors (~4 mm²), while weaker lithium disilicate requires ~4 mm² minimum, though clinical guidelines often recommend larger for safety.