Restorative - Week 9 PP

Question 1

Matrix Systems

Answer 1

A matrix system provides a “temporary wall” for the restoration process in class II, III and IV preparations

to hold the filling material in place - or else it would spill out

Question 2

Posterior Matrix Systems - Universal retainer

Answer 2

Universal retainer- also referred to as Tofflemire retainer
* A mechanical device that holds the matrix band snugly in position
* Positioned most commonly from the buccal surface of the tooth being restored

Question 3

Matrix Band

Answer 3

• Thin, flexible stainless steel material

The two designs most commonly used are:

• Universal band: Selectred for the class II preparation when the proximal box is prepared to a minimum depth and width and the cusps are intact

Extension band: Selected for the deeper class II
preparation requiring gingival extensions

Question 4

Design of Matrix Bands

Answer 4

The design of the matrix band is such that when the ends of the band are brought together, the band will form a circle
* One side of the circumference of the circle will be smaller than the other side
The circumference guides you in placing the band:
* Smaller circumference: Gingival edge and is always positioned toward the gingiva
* Larger circumference: Occlusal edge and is always positioned facing toward the occlusal part of the tooth

Question 5

Contouring the Matrix Band

Answer 5

The center of the matrix band should be contoured in the proximal contact area so the final restoration will have proper contact with the adjacent tooth
* To contour the band, place on a paper pad. Using a burnisher or end of the mirror handle, rub against the inner surface of the band until the ends begin to curl

Question 6

Wedges

Answer 6

Class II restorations require a matrix band to act as an artificial wall for the tooth.
- The matrix band alone does not provide the anatomic contour required interproximally
- A wedge is inserted into the lingual embrasure to hold the matrix band firmly against the gingival margin of the preparation

Question 7

Types of Wedges

Answer 7

Wedges are made in various sizes, forms (triangular or round), and materials (wood or plastic)
* Most commonly used type of wedge is the triangular or round wooden wedge

Question 8

Considerations for wedges include:

Answer 8

• Wedge must be wide enough so that pressure is applied to apical and gingival walls of the preparation
• Wedge presses the band against the tooth and causes a slight separation of the teeth
• Wedge is slightly wider than the distance between the cervical portions of adjacent teeth

Question 9

Positioning Wedges

Answer 9

When positioning the wedge, #110 (Howe) pliers or
cotton pliers are the instrument of choice for
inserting the wedge firmly into the embrasure
* For posterior restorations, the wedge will be positioned from the lingual side
Improper wedge and band placement can result in
an overhang or in cupping

Question 10

Anterior Matrix Systems

Answer 10

A clear plastic matrix is used with anterior composite
resin or glass ionomer materials
* The clear plastic matrix is also referred to as the celluloid strip or Mylar strip
Used for a class III or IV restoration when the proximal wall of an anterior tooth is missing
No retainer is needed to hold the matrix in place,
making this system an easier application

Question 11

Anterior Matrix Systems - Plastic matrix and wedge serve the following
purposes during the restoration process:

Answer 11

• Matrix is placed interproximally before the etching and bonding of the tooth to protect adjacent teeth from these materials
• After the placement of composite material, the matrix is pulled tightly around the tooth to help in
  reconstructing its natural contour
• Clear plastic matrix allows the curing light to penetrate the material, thereby completing the curing process

Question 12

Sectional Matrix Bands

Answer 12

Posterior composite restorations require a different type of matrix system than is used with the universal band and retainer
A thin, polished Palodent-type matrix band and tension ring produce tight anatomic contact for composite resin materials in class II restorations
* The thin, contoured matrix band is positioned first
interproximally
* The wedge is firmly placed to close the cervical margin
* The prongs of the tension ring are placed between the band and the wedge

Question 13

Amalgam vs. Composite

Answer 13

Amalgam - Tofflemier Band
Composite - Sectional Matrix

Question 14

Matrix Systems for Primary Teeth

Answer 14

Universal retainer and the matrix band do not fit
primary molars properly because of the shape and
size of these teeth
* T-band and spot-welded bands are two types of matrix systems designed to provide the correct width and depth needed for proper restoration of primary molars

Question 15

T-Band - for pediatric patients

Answer 15

A copper band in the shape of a T
* When formed, the top portion of the T allows the
straight portion to adjust and fit the circumference of the primary molar
Preparing the T-band matrix involves:
* Bending the wings of the T-band to form a U-shaped trough
* Slipping the free end of the band loosely through the U formation
* Closing the wings, and pulling the free end to make a small loop of the band
* Holding the free end toward the facial surface, place the band loop on the tooth to be prepared