Bases, Liners, and Matrices Flashcards

The Automatrix system differs from the Tofflemire system primarily in that it:

Answer: Is a self-tightening matrix that needs no external retainer

The Automatrix system is a retainerless matrix that is self-contained and tightened by its own internal mechanism.

What thickness of remaining dentin requires placement of a protective base before an amalgam or composite restoration?

Answer: Less than 0.5 mm

When remaining dentin thickness is less than 0.5 mm, a protective base is required to shield the pulp from thermal and chemical insults.

Which type of matrix system is most appropriate for Class III and Class IV composite restorations?

Answer: Celluloid strip matrix

Celluloid (Mylar) strip matrices are transparent and used for anterior composite restorations to allow light curing through the band.

Zinc phosphate base is indicated primarily in situations requiring:

Answer: Thermal insulation under metallic restorations

Zinc phosphate provides excellent thermal insulation and compressive strength, making it ideal as a base under metallic restorations.

When removing the Tofflemire matrix after condensing amalgam, what is the correct sequence?

Answer: Loosen retainer first, then remove wedge, then remove band facially

The retainer is loosened first to free the band, the wedge is removed, and then the band is carefully pulled facially to avoid fracturing the marginal ridge.

Which liner is considered the gold standard for indirect pulp capping procedures?

Answer: Calcium hydroxide

Calcium hydroxide's high pH creates an alkaline environment that stimulates odontoblasts to form a reparative dentin bridge.

What is the main disadvantage of calcium hydroxide as a liner?

Answer: It dissolves over time and has poor compressive strength

Calcium hydroxide liners have low compressive strength and tend to dissolve if microleakage occurs, which can undermine the restoration.