matrices / orthodontic courses by indian dental academy
TRANSCRIPT
INTRODUCTION
In the late 1800’s the need for a matrix became apparent
when dentists recognized that the best way to treat a tooth affected
by dental caries on the approximal surfaces was by restoring its
anatomical contour and contacts with adjacent tooth. The matrix
was needed to provide the missing wall or walls and thus contain
the restorative material during the filling of the prepared cavity. Until
the late 1800’s, the rationale for treating carious lesions on the
approximal surfaces of teeth was based on either a restorative or a
prophylactic concept.
EARLY CONCEPTS OF TREATING APPROXIMAL CARIES
Restorative concept
The rationale for restorative treatment was to remove the
caries and fill the cavity with a suitable material. At this time,
however, restoration of the tooth to form and function was not of
general concern.
Prophylactic concept
The rationale for prophylactic treatment was premised on an
early theory of caries, which taught that caries began at the point of
contact between the teeth where pressure damaged the enamel -
the lesion being caused by the action of external corrosive agents.
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The method advocated the creation of a self - cleansing
space by removing diseased or healthy tooth structure from the
approximal surfaces, thereby achieving total and permanent
separation of teeth.
The self - cleansing space was indicated for the prevention of
caries, for the treatment of superficial caries, and to provide access
to deep caries.
The procedure was accomplished by the use of a file, the
oldest method of removing tooth structure.
The procedure as described by HARRIS(1848) required the
removal of one - third or more of the tooth and created a shoulder
at the cervical margin to maintain contact in this area and prevent
the teeth from drifting.
In the posterior regions, the separation was referred to a V -
shaped space. If the teeth required restorations, they were
designed so as not to encroach on the space created.
Even with these improvements however, the results observed
by the general practitioner led to condemnation of the procedure by
the profession at large. The main criticism of this technique, voiced
by patients and the practitioners and patients alike, concerned the
disfigurement of teeth. Not only did patients complain of disfigured
teeth, they also complained of impaction of food on the gingivae
and sensitivity of teeth due to exposed dentin.
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By 1887, the technique was contraindicated.
CONTOURED FILLINGS
Around 1890, practitioners changed the way they restored
teeth that had approximal lesions.
The concept was premised on a new theory of caries, which
taught the caries began below, not at the contact point of the teeth
as with the early theory of caries(MILLER 1904) and advocated the
restoration of the natural, or original contour and contact of the
tooth. As such a contoured filling
1. Would reestablish the proper form of the inter - proximal space
2. Maintain the function of the teeth
3. Ensure no breach in the continuity of the occlural aspect of the
dention.
4. Maintain the length of the arch
5. Prevent impaction of food
6. Maintain and promate the health of the gingivae as well as the
comfort of the patient
Thus BLACK(1890) brought a new and different meaning to
the ‘V - shaped’ space . An additional concept introduced
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concurrently prescribed extending the margins of the approximal
surfaces of the cavity on to facial and lingual surfaces of the tooth.
This concept not only facilitated the placement of contoured
fillings, but also placed the cavity margins within the range of
protective influences, reducing the possibility of recurrent caries.
EARLY MATRICES
The early advocates of contoured fillings included W. H
Atkinson, M .H WEBB and S.H GUILFORD.
They recognized that to fill a prepared cavity and produce a
contoured filling the practitioner required assistance in containing
the filling material without such assistance , over contour at the
cervical level and under contour at the occlusal level resulted.
The assistance came in the form of a matrix, which provided
for the missing walls of the prepared tooth and transformed a cavity
of two, three or more surfaces into a simple one.
In addition the matrix could be molded to assist in re-
establishing the natural contours of the tooth.
Early in its use, the matrix was subject to criticism. Some
believed that when a tooth was to be restored with direct filling gold,
the matrix did not allow for enough contour of gold to compensate
for the subsequent polishing and adapted too closely to the
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margins, thus providing the potential for inadequate condensation
of gold in these areas especially at the cervical area.
ORIGINAL MATRIX
1. JACK MATRIX
2. HUEY MATRIX
3. PERRY MATRIX
4. BRUNTON MATRIX
(A) CUSTOM MATRICES
I. Anatomic matrices II. Tie band matrix III. Continuous loop
matrix
1.Shellac matrix Perry matrix Herbst
2.Herbst matrix Clapp matrix Newkirk modifi
3.Hutchinson matrix Fillebrown matrix Soldred matrix
4.Hand matrix Black matrix Spot welded
5.Woodward matrix Andrews matrix Tinner’s joint
6.Rubber matrices Baker matrix Welded
circumferential
(i) Danforth matrix Abernethy matrix Rivet matrix
(ii) adapto matrix Hallenback matrix Collar / band
modification
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7.Sweeny matrix Markley modification Harrison
8.Ingraham - -----matrix Hampson modification Copper band
9.Sectional matrix with Pinch band
Bi- ting ring
10.Open face matrix
(B) MATRICES WITH RETAINERS
Although the early matrices were intended for use with direct
filling golds, these matrices were also recommended for use with
amalgam which has been introduced to America in 1830’s.
Because of its plasticity amalgam required a matrix for the
condensation and development of proper physical properties,
contour and inter proximal contact.
THE ORIGINAL MATRIX
The first recorded use of a matrix is of that introduced by
DWINELLE(1855). The matrix consisted of a band made from a
broad, thin piece of dense gold. The band was wedged firmly
against the tooth. However it was opened against the cervical
margin of the cavity of the preparation to allow space for
condensation of excess gold.
Although his own personal testimony and that of his peers
(Brophy 1886 , Jack 1887) point Dwinelle as the originator of the
matrix. Later, the original matrix was described as the metal band
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that was wedged against and supported by the adjacent tooth, but
was not attributed to any one inventor.
IMPROVEMENTS ON THE ORIGINAL MATRIX
With the new concept of contoured fillings, the matrix took on
added significance. The earliest matrices incorporating the new
concepts appeared in the late 1800’s and included the JACK,
HUEY, PERRY and BRUNTON MATRICES. As a group, these
matrices used various materials of unspecified thickness for the
band.
The materials included steel, platinum plate or foil, brass,
copper, phosphor - bronze, German silver and tin. Few of these
bands were precontoured.
JACK MATRIX
Jack matrix introduced in 1871, was accepted as the first
matrix to satisfy the concept of contoured fillings. The matrix
consisted of a slight wedge shaped piece of steel hollowed out to
create a depression on its face to correspond to the desired
contour.
The band was made in assorted sizes and shapes and was
put into place with forceps, the Adjacent tooth used for
retention. The band was then wedged with a boxwood wedge.
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MATRICING
Matricing is the procedure whereby a temporary wall is
created opposite to the axial walls surrounding areas of tooth
structure that were lost during tooth preparation.
It is used with restorative materials that are introduced in a
plastic state.
OBJECTIVES
The matrix should
1. Displace the gingivae and rubber dam away from the cavity
margins during introduction of the restorative material.
2. Assure dryness and non-contamination of the details and the
space to be covered with and occupied by the setting restorative
material.
3. Provide shape of the restoration during the setting of the
restorative material i.e band materials should be unyielding to
the enregies of insertion.
4. Maintain shape during the hardening of the materila.
5. Confine the restorative material within the cavity proparation and
predetermined surface configration.
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MATRICES FOR CLASS I CAVITY PREPARATIONS
Double banded Toffelmire for class I.
Turn the large vice moving knob until the slotted vice is about
¼ inch from the inner end of the retainer. Loosen the screw until its
painted end is clear of the slotted vice.
Make a loop out of the universal band creating an edge with a
narrow circumference.
The narrow circumference is placed gingivally and the wide
circumference edge is placed occlusal.
The free ends of the band are inserted into the vice while the
looped end of the band extends away from the retainer.
Always be sure the slotted end of the vice is facing gingivally.
This will facilitate easy occlusal removal of the retainer.
Tighten the vice screw to lock the band in the vice. Guide the
looped end of the band gently over the tooth. The size of the loop
may be increased or decreased by turning the vice moving knob.
With the band in position around the tooth, tighten the vice
moving knob.
Ideally the retainer should be parallel and adjacent to the
facial surfaces of the quadrant of the teeth being operated on.
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An additional small piece of matrix band material is that
contoured to the facial or lingual axial configuration of the
contemplated restoration and inserted between the tooth and the
previously positioned and retained matrix in the area of the facial or
lingual extension of the cavity preparation.
This piece of material should overlap over the margins of the
extension by about 1.5 - 2mm circumferentially.
With a beaver-tail burnisher, create a separation between the
two bands. Select a wedge that will create and maintain the proper
separation between the two bands and thereby enable the
formation of the proper contour facially and / or lingually.
Cover the wedges with softened compounds and insert it
between the two bands and cool to harden.
MATRICES FOR CLASS II CAVITY PREPARATIONS
a) SINGLE-BANDED TOFFELMIRE FOR CLASS II
This is the most practical matrix for class II cavity
preparations. Its use is made universal by the easy application and
removal of the band to and from its holder without disturbing the
condensed material.
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PROCEDURE
The basic steps are repeated from the previously described
double banded arrangement.
If the cavity preparation involves one proximal surface only
and there is a substantial difference between the heights of the
interproximal gingiva on the mesial and distal sides of the tooth, the
matrix band should be trimmed so that it is narrower on the side
where the interproximal gingiva is more occlurally located.
It may also be possible to use matrix bands with only one
gingival projection, which should coincide with the proximal side
where the interproximal gingiva is more apically located.
If the gingival extension of the proximal portion of the cavity
preparation is more apically located than gingival lines facially and
lingually, there is a danger of cutting the gingival tissues facially
and lingually in using a band with a straight gingival edge.
In this situation it is necessary to reduce the occlusal - apical
width of the band facially and lingually or to use a band with apical
projections which coincide and cover the gingival extension of the
proximal portion of the cavity preparation.
In preparation with subgingival margins, especially at the
axial angles or any surface protrusion of the tooth, the edges of the
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band occasionally encounter the gingival margin and become bent
inward, preventing further seating of the band.
For this reason there should be unprepared, exposed tooth
surface apical to the gingival margin of the preparation to support
the band in its apical path and to prevent its inward collapse or
bending. This may necessitate gingival retraction or cutting.
Also in these situations, the band edges should be guided in
their apical path by placing a flat - bladed, blunt instrument between
the band and the adjacent unprepared tooth surface apical to the
gingival margin.
Although it is preferable to put the retainer in the buccal
vestibule, parallel to the adjacent teeth, sometimes, due to shallow
sulcus or sizable buccal involvement of the tooth in a activity
preparation, the retainer is placed on the lingual. This usually
necessitates a contrangled retainer.
However a retainer should never be located at right angle to
the facial or lingual surfaces of the teeth operated upon as this will
drastically change the occluso-apical contour of the band.
As soon as the band is in place and all cavity margins can be
seen inside the matrix, a wedge, comparable to the dimensions of
the future gingival embrassure is chosen and tied(always from the
opposite side of the retainer attachment).
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Using a ball burnisher from within the cavity preparation,
shape the matrix material to create the out line of the contact and
contour of the future restoration.
If the cavity has buccal or lingual extension, repeat the
modifying steps in the double-banded Toffelmire application.
For all Toffelmire applications, after the insertion and initial
hardening and manipulation of the restorative material, the wedges
and secondary band are removed. Then the retainer is loosened
and disengaged. The primary band is bent against adjacent tooth
surfaces and removed from between the teeth in an occlusal
direction, while being pressed against the adjacent tooth.
If the contact area is extremely tight and the band is resistant
to removal, it is a good idea to cut the band on the opposite side of
the retainer, remove the roughened portion of the band and then
pull it buccal-lingually with pressure against the adjacent tooth.
b) IVORY MATRIX NO.1
The band encircles a posterior proximal surface so it is
indicated in unilateral class II cavities.
c) IVORY MATRIX NO.8
The band encircles the entire crown of the tooth so it is
indicated for bilateral class II cavities.
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d) BLACK’S MATRICES
i)Black’s matrix for simple cases is recommended for a majority of
small and medium size cavities
PROCEDURE
Cut a metallic band so that it will extend only slightly over the
buccal and lingual surfaces of the tooth.
To prevent a wrap, around holding ligature from slipping off
the band and the band sliding gingivally. The corners of the gingival
ends are turned up to hold the ligature.
ii) BLACK’S MATRIX with a gingival extension to cover the
gingival margin of a subgingival cavity.
In this form of extension is created in the occluso-gingival
width of a band to cover the gingival margin of a subgingival
cavity. The retaining procedures are the same as for the previous
type of Black’s matrix.
e) SOLDERED BAND OR SEAMLESS COPPER BAND MATRIX
These are indicated for badly broken teeth, especially those
receiving pin retained amalgam restorations, with large buccal and
lingual extension i.e Class II design preparation
PROCEDURE
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A stainless steel band is cut according to the measured
diameter of the crown of the tooth, then the two ends are soldered
together or a seamless copper band is selected so that it barely
clears the diameter of the tooth in the cervical area.
Either the band could be heated in a flame until it glows red
light. It is then quenched in alcohol thus softening the band for easy
handling.
With curved scissors, fasten the band so its gingival periphery
corresponds to the gingival curvature and the CEJ.
The band is then smoothed to remove rough edges cervically
and occlusally. With containing pliers contour the band to produce
the proper shape in the contact area.
Areas of the band in the contact area are reduced to a paper
thinness using a coarse sand paper disc.
Then they are recontoured . Next the band is seated on the
tooth and tightened at the cervical end by pinching a ‘tuck’, using a
flat bladed plier at the gingival edge in the area accessible to the
plier.
To stabilize the band and prevent cervical flashes of
amalgam, wedges are placed gingival to the cervical margin of the
preparation.
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The external portions of the matrix and the wedges are
covered with compound to further stabilize the matrix. A wire is
inserted facio- lingually in the compound to further stabilize it.
Apply a heated ball burnisher from the inside of the cavity to
the band, softening the external compound and insuring the proper
contour, contacts and embrasures.
After condensation and initial covering, the compound is
removed and the matrix is cut at the area of the tuck.
With a plier or hemostat, grip the band at either side of the
scissors, cut and tear through each thinned contact portion to
remove the band without damaging the proximal region of the
amalgam.
f) THE ANATOMICAL MATRIX
This is the most efficient means of reproducing contacts and
contour.
It is entirely hand made and contoured specifically, for each
individual case. It is specially useful in mutilated teeth. It is
indicated for class II designs.
PROCEDURE
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A piece of “0.001 - 0.002” stainless steel matrix band 1/8th in
width is drawn between the handle of a pair of festooning scissors.
This procedure facilitates the adaptation of the free ends of the
matrix to the proximal surface of the tooth.
The matrix is cut to proper length. It must extend well beyond
cavity margins. To obtain a proper length the center’s of the
proximal buccal and proximal lingual cusps are used as a guide.
The matrix band is contoured with contouring pliers. The band is
then trimmed so that the matrix will extend well below the gingival
margin of the cavity and at least 2mm beyond the buccal & lingual
margin of the cavity.
A wedge is selected and shaped to conform to the gingival
embrasures, and it is then placed in warm water to soften it slightly.
Two small cones of compound are warmed in hot water.
These compound cones are forced one at a time, using thumb and
finger pressure into the buccal and lingual embrasures.
The pressure is maintained until the compound has flowed
evenly over the entire buccal and lingual surface of the adjacent
teeth. A wire staple is constructed from a paper clip.
The staple is heated in a flame and forced into the compound
in the buccal and lingual embrasures. This adds to the stability of
the matrix by locking together the 2 pieces of the blacking
compound.
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A warm ball burnisher is used to soften any compound that
has been forced between the matrix and the adjacent tooth. The
matrix is burnished lightly against the contacting tooth.
After initial hardening of the inserted restorative material, the
compound is cracked at its occlusal junctions using a sharp chisel
or knife.
The wedges are removed using a hemostat and the band is
curled backwards against the adjacent tooth and withdrawn
buccolingually, with pressure against the adjacent proximal surface.
g) ROLL - IN - BAND MATRIX (Auto matrix)
h) S - SHAPED BAND
This is used for class II cavity preparations. Procedural
instructions are exactly as described in class III preparations
3)MATRICES FOR A CAVITY PREPARATION FOR AMALGAM RESTORATION ON THE DISTAL OF THE CUSPID
a) The S - shaped matrix
This is an ideal matrix for class III cavity preparation on the
distal of the cuspid, with either a labial or lingual access.
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PROCEDURE
One half to one inch of regular strip matrix 0.001 - 0.002 in
thickness is used. A mirror handle is used to produce the S-shaped
in the strip. The band is contoured over the labial surface of the
cuspid and the lingual surface of the adjacent bicuspid.
With contouring pliers, the strip is contoured in its middle part
to create desired form for the restoration. It is then placed inter
proximally and wedged firmly apical to the gingival margin and
covered with compound at its facial and lingual ends.
The remaining procedure is similar to those of the anatomic
matrix.
4) MATRICES FOR CLASS III DIRECT TOOTH COLOURED RESTORATIONS
These are usually transparent plastic matrix strips. For resin’s
cellophane strips are used. Mylar strips may also be used.
a) Matrix for class III preparations with teeth in normal alignment.
The suitable plastic strip is burnished over the end of a steel
instrument. Eg :- handle of a tweezer , to produce a BELLY in the
strip. This will allow for curvature which if properly contoured and
designed, will reproduce the natural proximal contour of the tooth.
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The strip is cut to allow the belly to be placed where the
contact is desired. In placing a plastic strip between the teeth, it
should be cut as wide as the tooth is long.
The corners of the strip should be trimmed therefore , to allow
for better adaptation to the tooth and to prevent any excess material
from forming on and beyond the facial or lingual margins.
The length of the strip should be just sufficient to cover the
labial and lingual surfaces of the tooth.
A wedge is trimmed and applied to hold the strip in place. For
labial approach use fingers of the left hand for holding the strip
firmly against the lingual surface of the tooth while the material is
being placed in the cavity.
b) Matrix for class III preparation in teeth with irregular alignment
PROCEDURE
A suitable plastic strip is contoured and adopted as described
previously and then removed.
For a labial approach preparation a compound impression is
taken of the lingual surface. The compound is allowed to overlap
the adjacent teeth. It is cooled and then removed.
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The compound impression should show an imprint of the
cavity preparation.
The compound impression is then warmed. The surface is
softened without distorting the form of the entire impression. This
can be done by holding the impression close to the flame only for a
moment.
The strip is then placed into position again, followed by the
compound impression against the strip, assuring perfect adaptation
of the matrix to the cavity on the lingual surface. The material is
then introduced from the labial.
c) MATRIX FOR TWO SMALL PROXIMAL PREPARATIONS IN CONTACT WITH EACH OTHER
An appropriate plastic strip is folded with one end slightly
longer than the other.
A loop ½ inch in diameter is formed in the matrix strip. The
loop is flattened and ceased with a finger, making a T - shaped and
trimmed. The trimmed matrix is then placed between the teeth.
For labial approach preparations, the strip is held over the
lingual surface with the finger while the cavities are filled.
5) MATRICES FOR CLASS IV PREPARATIONS FOR DIRECT TOOTH COLOURED MATERIALS
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a) The plastic strip for inciso proximal cavities
PROCEDURE
A suitable plastic strip is folded at an angle into an L - shaped
then sealed with a plastic cement or any adherence that does not
react with tooth coloured material.
One side of the strip is cut so that it is as wide as the
length of the tooth.
The other side is cut so that it is as wide as the width of
the tooth.
The strip with a wedge in place is adapted to the tooth
b) ALUMINIUM FOIL INCISAL CORNER MATRIX
These are ‘stock’ metallic matrices shaped according to the
proximo - incisal corner and surfaces of anterior teeth. They can be
adapted to each specific case.
PROCEDURE
A corner matrix closest in size and shape of the lost area of
the tooth is selected. It is trimmed gingivally so that it coincides with
the gingival architecture and covers the gingival margin of
preparation.
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As it is readily deformable, shape it with the thumb and first
finger until it fits the mesio distal and labio - lingual dimensions of
the tooth. Loosely place the wedge allowing space for the matrix
band thickness.
Partially fill the preparation and then the corner matrix
preferably after venting the corner.
Apply the partially filled matrix over the partially filled tooth
preparation at its predetermined location between the loosened
wedge and the tooth.
c) TRANSPARENT CROWN FORM MATRICES
These are ‘stock’ plastic crowns which can be adapted to
tooth anatomy.
In bilateral class IV preparations use the entire crown form.
In unilateral class IV cut the plastic crown inciso -
gingivally into two halves and use only the side
corresponding to the location of the preparation.
PROCEDURE
Choose the crown form with the size and shape close to the
tooth to be restored.
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For a unilateral class IV, after cutting the crown from inciso -
gingivally, so that the correct incisal angle of the crown form
matches the last tooth incisal angle. If for bilateral class IV keep the
crown as it is.
Trim the crown form gingivally, so that it coincides with the
gingival architecture and completely covers the gingival margin of
the preparation.
Check the matrix to ensure that it will recreate proper contact
and contour. Then remove the matrix and thin it at its contact area
with a sand paper disc. It should be perforated at the incisal angle.
Completely fill the matrix with the restorative material and
partially fill the preparation with the restorative material.
Place the filled crown form on the tooth in the desired
location. The wedge is then tightened.
d) ANATOMIC MATRIX
Prior to preparing the teeth, study model for the affected tooth
together with at least one intact adjacent tooth on each side is
made.
It is preferable, especially in multiple involvement. The
defective area is restored on the study model in a fairly heat
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resistant material ( plaster, acrylic resin, blacking compound,
plasticine, etc) to the appropriate configuration.
A plastic template is made for the restored tooth on the model
using a comb of heat and suction consequently to draw the
mouldable material onto the study model.
The template is trimmed gingivally to fit the tooth and
adjacent peridontal architecture. It should seal on atleast one
unprepared tooth on each side.
This is the matrix which should be vented by perforating the
corners of its part corresponding to the future restoration.
6) MATRICES FOR CLASS V AMALGAM RESTORATION
a) WINDOW MATRIX
This matrix is formed using either a Tofflemire matrix or
copper band matrix.
PROCEDURE FOR USING THE TOFFLEMIRE MATRIX
The contrangle retainer is applied at the side of the tooth that
does not have the preparation. A window is cut in the band slightly
smaller than the outline of the cavity (perforated windowed bands
are available). Wedges are placed mesially and distally to stabilize
the band.
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PROCEDURE FOR USING THE COPPER BAND
A seamless copper band is selected that is just larger than
the prepared tooth. Fasten and adjust the band to the tooth.
A window is cut coinciding with the cavity but smaller in
diameter. The edges are smoothed.
b) THE S - SHAPED MATRIX
This is usually indicated for a proximal extension of a buccal
or lingual class V preparation.
7) MATRICES FOR CLASS V PREPARATIONS FOR DIRECT TOOTH COLOURED RESTORATIONS
a) Anatomic matrix for non light cured direct tooth colored
materials.
PROCEDURE
The class V cavity may be preliminary filled with inlay wax or
gutta - percha and trimmed to the proper contour. The wax and the
tooth are then coated with cocoa butter or mylar strip and
compound impression is taken of the tooth surface to be restored.
Adjacent surfaces are to be included in the impression. After the
compound has cooled, it is removed and the wax is removed from
the cavity.
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A mix of the restorative material is made and placed into the
cavity, and the compound matrix is placed into position and held
securely in place under pressure until the material sets.
SUMMARY / CONCLUSION
Although there have been very few investigations conducted
on this subject, it is clear that no matrix technique is capable of the
exact replication of normal anatomic contour of restored teeth.
Overall the anatomic matrix procedures must closely reproduce
normal tooth contours.
Wedging is universally imperative in order to eliminate cervical
flash of restorative material.
Some of the clinical significance is the fact that circumferential
matrix bands retained by tightening devices(Toffelmire) have
been shown to deform tooth structures.
Passively inserted matrix bands like anatomic matrix and T -
shaped bands etc have no deformative effect on the remaining
tooth structure.
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