Module 3 Matrices

What is the purpose of a matrix?

• To replace missing walls of a tooth,

• provide contours during restoration,

• prevent interproximal overhangs.

What are the main types of matrices?

• Tofflemire matrix,

• Automatrix,

Describe the Tofflemire system?

• utalizes a retainer and a band system.

• matrix band is placed into the retainer (diagnal slot and guide channels)  and then both are placed into the mouth.

Describe the Automatrix system?

A matrix system without a retainer or holder,

Describe the anterior matrix systems

• A clear plastic matrix is used (Mylar Strip)

• Used for class III and IV restorations

• No retainer is needed 

• easy application

What advantages does a clear plastic matrix provide?

Allows curing light penetration and protects adjacent teeth during etching and bonding.

Describe the placement of the anterior matrix

• is placed interproximally before etching and bonding

• after placing composite material the matrix is pulled tightly around the tooth to contour it

What is a crown matrix form?

A thin plastic form shaped like a crown, used for Class IV restorations.

What is a T-band?

A matrix that does not use a retainer, commonly used in pediatric dentistry because of it’s boxed shape.

What is a universal (Tofflemire) retainer?

• A mechanical device that holds the matrix band tightly around the tooth

• Is positioned in the buccal surface of a tooth

Where is the diagonal slot of the Tofflemire retainer positioned?

Always toward the gingiva.

On which surface is the Tofflemire retainer positioned?

On the facial or buccal surface of the tooth being restored.

• it extends outside the mouth

How far should the matrix band extend below the gingival margin and above the occlusal surface?

Gingival margin: Below Approximately 1.5 mm.

Occlusal Surface: Above aprox. 2.0mm

What are the two different matrix bands?

Universal Band

Extension Band

Describe the universal matrix band

• used for class II with minimal depth and width, and the cusps are intact

• Is used for the Tofflemier retainer

Describe the extension band

• for deeper class II restorations tat require gingival extensions

Describe the shape and positioning of the matrix band 

Shape: circle that has a smaller circumference edge and and a longer one

Position:

• Large circumference must face the occlusal surface

• the smaller end must face the gingiva

What should be done if the matrix band becomes creased or bent?

Smooth it by “ironing” — running the handle of a mouth mirror inside the loop to remove bends.

What is the purpose of a wedge?

• prevent overhangs

• hold the band securely,

• adapt band to gingival contours,

• slightly separate teeth for proper contact when band is removed.

What are the two main types of wedges and when is each one used for?

Wooden:

Used only with amalgam

Plastic:

Used with composites or amalgams

What are sectional matrix systems used for and what is their purpose?

• Class II composite restorations to restore proper anatomical contact.

• It helps create tight anatomical contact and seals the cavity preparation.

What components make up a sectional matrix system?

A thin stainless-steel band, a wedge, and a tension ring (Garrison ring).

• The band is placed first, then the wedge is placed interdentally and lastly the gartison ring.

What is one brand of sectional matrix system?

Palodent matrix.

Is it legal for dental assistants in Arizona to place and remove matrices?

Yes, dental assistants in Arizona are legally allowed to place and remove matrix systems.