matrix system in restorative dentistry

1. Copyright 2003, Elsevier Science (USA). All rights reserved.
Matrix Systems for
Restorative Dentistry
Chapter 49
Copyright 2003, Elsevier Science (USA).
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2. Copyright 2003, Elsevier Science (USA). All rights reserved.
Introduction
A matrix system provides and takes the place
of the proximal tooth surface that was removed
to restore the proximal contours and contact to
their normal shape and function.

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Posterior Matrix System
 Universal retainer
• Also referred to as the Tofflemire retainer.
This device holds the matrix band in
position. The retainer is positioned most
commonly from the buccal surface of the
tooth being restored.

4. Copyright 2003, Elsevier Science (USA). All rights reserved.
Components of a Universal Retainer

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Posterior Matrix System− cont’d
 Matrix bands
• Matrix bands are made of flexible stainless
steel and are available in premolar, molar,
and universal sizes and thicknesses.
• The larger circumference of the band is
the occlusal edge and is always placed
toward the occlusal surface.
• The smaller circumference of the band is
the gingival edge and it is always placed
toward the gingiva.

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Fig. 49-2 Types of matrix bands.

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Wedges
 A wedge is either triangular or round and
made of wood or plastic.
 The wedge is inserted into the lingual
embrasure to position the matrix band firmly
against the gingival margin of the preparation.

8. Copyright 2003, Elsevier Science (USA). All rights reserved.
Fig. 49-6 A wedge correctly positioned.

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Automatrix System
 The automatrix system is an alternative to a universal
retainer.
 There is no retainer used to hold the band in place.
 Bands are already formed into a circle and are
available in assorted sizes in both metal and plastic.
 Each band has a coil like autolock loop.
 A tightening wrench is inserted into the coil and
turned clockwise to tighten the band.
 When finished, the tightening wrench is inserted into
the coil and turned counterclockwise to loosen the
band.
 Removing pliers are used to cut the band.

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Matrix Systems for Primary Teeth
 The T-band is a T-shaped copper band.
 When formed, the top portion of the T allows
the straight portion to adjust and fit the
circumference of the primary molar.

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Fig. 49-7 Example of copper T-band used for primary molars.

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Preparing the T-Band Matrix
 The wings of the T-band are bent to form a U-
shaped trough.
 The free end of the band is slipped loosely
through the U formation.
 The wings are closed, and the free end is
pulled to make a small circle of the band.
 Holding the free end toward the facial
surface, place the band on the tooth to be
prepared.

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 A spot-welded band is a form-fitted band
placed around a prepared tooth, then
removed and placed in a smaller form of a
welder that fuses the metal together to make
a custom band.
Additional Matrix Systems for Primary
Teeth

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Fig. 49-8 Spot-welded band.

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Preparing a Spot-Welded Matrix Band
 Measure ¾ to 1 inch of stainless steel matrix
material.
 Fit the matrix materials around the prepared
tooth.
 Adapt the band, making sure the ends of the
matrix material is at the facial surface for
visibility and control.
 Holding the ends tightly, remove the band in an
occlusal direction.
 Place the band in the spot welder.
 Spot-weld the matrix at three positions.

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Matrices for Composite Restorations
 A plastic matrix, also referred to as a
celluloid matrix or mylar strip, is used for
class III and IV restorations in which the
proximal wall of an anterior tooth is missing.

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The Use of a Clear Matrix
 The matrix is placed interproximally before
the etching and priming of a tooth. This
protects adjacent teeth from these materials.
 After placement of composite material, a
matrix is pulled tightly around the tooth to
help reconstruct its natural contour.
 The clear plastic matrix allows the curing light
to penetrate the material and complete the
curing process.

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Sectional Matrices
 A thin polished palodent-type band and a
tension ring produce a tight anatomic contact
for composite resin materials for class II
restorations.

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Fig. 49-10 Sectional matrices.