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Sectional matrix: Step-by-step directions for their clinical use

Article  in  British dental journal official journal of the British Dental Association: BDJ online · January 2016
DOI: 10.1038/sj.bdj.2016.18

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Sectional matrix: Step-by-step IN BRIEF
• Discusses the clinical technique for
directions for their clinical use restoring Class II cavities using a

PRACTICE
sectional matrix.
• Suggests a higher separation than the
matrix thickness must be achieved,
V. Alonso de la Peña,1 R. Pernas García1 and R. Pérez García*1 which subsequently facilitates its proper
placement.
• Advises that the matrix cannot be placed
on the cavity floor; it has to exceed the
gingival margin of the preparation.

The sectional matrix is the best way to achieve a strong contact point in Class II restorations with composite resin in the
posterior dental sector. The pre-wedging is essential to get a separation between teeth which avoid the matrix deformation
during its insertion. This article describes the clinical technique for restoring Class II cavities using a sectional matrix.

INTRODUCTION field. The isolation should be wide, to obtain Another way to achieve a separation
In the posterior dental segment, the inter- better access and visibility11 for the dentist between the teeth that need to be restored
proximal contact area is located in the mid- and the assistant. The rubber dam is main- is by placing an orthodontic separator a
dle third, or at the union of the occlusal tained in position with a large metal frame few days before. These elastic separators
third with the middle third of the proximal (Adult Rubber Dam Frame. Hu-Friedy Mfg. are used in orthodontics for metallic bands
surfaces.1 When a Class II restoration is per- Co., Chicago, IL, USA). insertion.
formed, obtaining a strong and anatomical To achieve a wide operating field, the clamp
proximal contact area prevents food impac- must be placed as far back as possible in the
tion and periodontal disease, helping to molars, and in premolars it should be placed at
maintain papillary health. It also prevents least two teeth distally to the tooth that is going
dental migration and decay.2,3 The studies to be restored. This avoids the clamp interrupt-
published up to this day support that, in ing the proper placement of the wedge, matrix,
Class II restorations with composite resin, the or ring (Fig. 1). If this is not possible, the use
sectional matrix with rings provides more of a wingless clamp or another that does not
anatomical and stronger contact areas than extend into the interproximal area would be
a circumferential matrix.4–7 indicated (Fig. 2). In the opposite direction, the
Isolation of the operative field with a rub- authors like isolating up to the central incisor.
ber dam is recommended,8 although, there In deep cavities, cutting the interproximal strip
are clinical studies that did not find differ- of the rubber dam may be indicated to prevent Fig. 1 Incorrect placement of the wedge and
ring due to the interference of the clamp fin
ences in the survival rate of restorations in it from invading the gingival floor and hinder-
the posterior sector where isolation was done ing the clinical procedure.
with cotton rolls and aspiration, in compari-
son with a rubber dam.9,10 Pre-wedging
This article describes the clinical technique In order to achieve a tight proximal con-
for restoring class II cavities using the sec- tact the use of the pre-wedging technique
tional matrix. is recommended. 6 Before removing the
decayed tissue, the use of protective wedges
DESCRIPTION OF TECHNIQUE with a metal fin (FenderWedge, Directa AB,
UpplandsVäsby, Sweden) is essential. They
Operative field preparation avoid damaging the wall of the adjacent
The operatory field isolation is the first tooth. Even so, the metal fin can be drilled
step; the authors prefer working with a rub- while the cavity is being prepared.
ber dam (Rubber dam. Hygenic.Coltène/ A higher separation than the matrix thick-
Whaledent, OH, USA) to isolate the operatory ness must be achieved, which subsequently
facilitates its proper placement. Therefore, it
1
University of Santiago de Compostela, School of Den- is preferable to use wide wedges and insert
tistry, Entrerríos s/n, Santiago de Compostela, Spain them with a curved mosquito haemostat to
*Correspondence to: Rocío Pérez García
Email: rochi_perez@hotmail.es make a strong pressure and insert them com-
pletely. Sectional matrices are very thin and
Refereed Paper easily deformed. The insertion of the wedge Fig. 2 Isolation of the operatory field with
Accepted 9 November 2015 a wingless clamp which does not prevent the
DOI: 10.1038/sj.bdj.2016.18 can cause a distance between the rubber dam
proper placement of the wedge
© British Dental Journal 2016; 220: 11-14 and the tooth contour at that level.

BRITISH DENTAL JOURNAL VOLUME 220 NO. 1 JAN 15 2016 11

© 2015 British Dental Association. All rights reserved

 PRACTICE

Cavity preparation a curved mosquito haemostat and waiting a matrix must be centred, with similar seg-
The removal of carious tissue can result in short interval of time until there is enough ments towards the buccal and lingual side.16
unsupported enamel in the proximal cav- separation. If the interference is located near It is important to keep in mind that the
ity floor, which must be eliminated.12 For the occlusal surface, it can be resolved with matrix can be moved in the direction of the
this, a margin trimmer13 (Margin Trimmer a metal composite instrument (Composite wedge insertion.
MT26, Hu-Friedy Mfg. Co., Chicago, IL, USA) Instrument, PFI11, Hu-Friedy Mfg. Co., The Composi-Tight Soft-Face 3D Ring
or a cylindrical burr (Komet 10839, Gebr. Chicago, IL, USA) in order to separate the (Garrison Dental Solutions, Spring Lake, MI,
BrasselerGmbh. KG, Lemgo, Germany) that teeth. The matrix cannot be placed on the USA) is now placed to seal the buccal and
cuts only on the flat end was used. There can cavity floor; it has to exceed the gingival lingual embrasures. This ring has silicone
also be used a sonoabrasive system,14 with margin of the preparation. ends with a wedge shape to adapt the matrix
sonic tips for the preparation of interproxi- Once the matrix is positioned, a wooden to the embrasures and avoid the overhang
mal cavities. wedge (Soft Wedges, Garrison Dental, Spring of the restoration (Fig. 4). It also has a space
Once the cavity preparation is finished, the Lake, MI, USA) is inserted with a curved for the wedge to achieve a good fit to the
FenderWedge is removed. At this time, there mosquito haemostat, applying the necessary gingival area (Fig. 5).
is a direct view of the proximal surface of force in order to adapt the matrix closely to Frequently, these procedures can cause
the adjacent tooth. If decay is located on the the gingival contour of the proximal box gingival bleeding, nevertheless, if the tech-
proximal surface, it can be treated directly (Fig. 3). It must also remain below the proxi- nique was adequate, there would never be
without removing healthy tissue, like the mal cavity floor. If the wedge remains above contamination inside of the cavity even if
marginal ridge. the cavity floor, it will cause a convexity of the rubber dam is not used (Fig. 6). A water-
the matrix towards the interior of the cav- tight compartment has been achieved by the
Matrix placement ity. The wedge has a double function: to get matrix being intimately adapted to the cav-
The matrix must be placed without pres- a separation between teeth which compen- ity walls. Due to the pressure caused by the
sure. Matrices are very thin (0.038  mm.) sates the matrix thickness for obtaining a ring or the wedge, small remains of gingival
(Slick Bands, Garrison Dental Solutions, strong interproximal contact, and to adapt tissue or detached fragments of enamel may
Spring Lake, MI, USA) and easily deformed the matrix intimately to the contour of the stay inside the cavity. They must be removed
if pressure is applied while placing them. If tooth all around the cavity floor. The inser- with an explorer and, with the same instru-
the matrix cannot be placed easily, a wide tion of the wedge can be done from either ment, the sealing of the contour is checked.
wooden wedge (Hawe Sycamore Interdental lingual6 or buccal15 side or even from both,
Wedges, KerrHawe, Orange, CA, USA) can provided that the matrix remains intimately Polishing phase
be inserted, exerting a strong pressure with adapted to the cavity floor. The sectional Once the restoration is finished, it needs to
be polished. In the interproximal area, the
authors prefer the use of diamond-metal
finishing strips (Diamond Finishing Strips
cxds3-superfine, Edenta AG, Hauptstrasse,
CH Switzerland), due to their ability to pass
more easily through the contact area with-
out breaking. They have a sawtooth central
fragment that is sometimes useful to intro-
duce it from the occlusal side. In order to
polish the embrasures and round off the
marginal ridge, discs are employed, placing
the active surface towards the head of the
Fig. 3 (a) Absence of unsupported enamel. Proper matrix adaptation to the contour of the contra angle and separating the teeth with
tooth and sealing of the embrasures. (b) Restoration completed with a correct contact area, a metal composite placement instrument if
checked with dental floss there is not enough space for the disc. The

Fig. 4 (a) Distal decay in tooth 14. Pre-wedging and protection of the adjacent tooth with a wedge with a metal fin. (b) The ends of the ring
have a wedge-shape, which adapts to the embrasures avoiding the overhang of the restoration. (c) If it is possible, the isolation should be done
two teeth distally to the teeth that are going to be restored, and up to the central incisor

12 BRITISH DENTAL JOURNAL VOLUME 220 NO. 1 JAN 15 2016

© 2015 British Dental Association. All rights reserved

 PRACTICE

Fig. 6 Orthodontic patient where isolation

with rubber dam is not possible. Despite this,
a proper technique achieves a watertight
compartment without the contamination of
blood and saliva

Fig. 5 (a) Matrix has to exceed the gingival margin of the preparation, with similar segments
towards buccal and lingual. The removal of the wedge or the insertion of the matrix can cause
bleeding. (b) Proper placement of the wedge and ring. The ends of the ring have a space for the
wooden wedge. This allows a better gingival adaptation of the matrix. (c) Ring Composi-Tight
Soft-Face 3D sealing the buccal and lingual embrasures. (d) The polishing of the interproximal
surface and the effectiveness of the contact area is checked with dental floss. If it frays, it will
indicate irregularities that must be corrected

Fig. 7 In order to polish, the embrasures

recommended discs have a square centre separation of the teeth is more effective discs are employed, placing the active surface
which impedes the mandrill from rotating with rings than with wooden wedges20,21 and, towards the head of the contra angle. These
and not the disc (Polishing disc 12.7 DF‑M, therefore, is recommended by some manu- discs have a square centre which impedes the
mandrill from rotating and not the disc
AXIS Dental, Crissier, Switzerland) (Fig. 7). facturers..22–24 By contrast, the authors con-
Finally, the polishing of the interproximal sider the pre-wedging to be more effective.
surface and the effectiveness of the contact The Triodent system, with the V3 Ring
area are checked with dental floss.4,17 If it (Sectional Matrix System, Dentsply, Katikati,
frays, it indicates irregularities that must be N.Z.) and Palodent Plus (Sectional Matrix
corrected. System, Dentsply Caulk, Milford, DE, USA)
are systems of sectional matrix with the
DISCUSSION same elements. Once the cavity is finished,
An in  vitro study comparing a different both systems indicate removal of the metal
circumferential matrix with a sectional fin of the wedge (WedgeGuard, Palodent
matrix (Palodent, DentsplyDetrey GmbH, Plus, Dentsply Caulk, Milford, DE, USA) and
Konstanz, Germany) determined that the inserting the matrix with the wedge placed
sectional matrix reproduces the strongest interproximally.24,25 The authors believe that
contact areas, but no system reproduced a the wedge must be removed before inserting
similar form to an intact tooth.18 Another the matrix, otherwise it is more complicated
study done with plastic teeth from a man- to insert the matrix behind the wedge and
nequin model suggests that an undesirable achieve a watertight compartment without
concavity appears in the contact area when deforming it.
circumferential or sectional matrices are We consider that previous teeth separation
used, the latter showing a higher incidence is essential to placing the matrix without
of a concave contour.19 This may be because changing its morphology. A clinical tech-
if there is not enough separation between the nique with an adequate placement of the
teeth, the sectional matrix is deformed by the matrix, as well as a proper positioning of
marginal ridge of the adjacent tooth, pro- the wedge and the ring, will avoid the irregu-
Fig. 8 Small concavity in the matrix towards
ducing said concavity. Therefore, an effec- larities on the cavity floor and the overhang the cavity. This could be caused by the
tive pre-wedging is essential and, once the on the embrasures. marginal ridge when the previous separation
matrix is placed, a wide wooden wedge must There are conflicting studies in relation to is not enough. A lack of adaptation of the
be placed for obtaining enough separation the use of a sectional matrix in MOD resto- matrix on the floor is seen. This is prevented
and avoiding this problem (Fig. 8). rations. Wirsching et al.26 in a clinical study, by placing a wedge on the opposite side or
with a wedge on each side
It has been affirmed that the previous say there are no differences in the strength

BRITISH DENTAL JOURNAL VOLUME 220 NO. 1 JAN 15 2016 13

© 2015 British Dental Association. All rights reserved

 PRACTICE

6. Loomans B A, Opdam N J, Roeters F J, Bronkhorst E M,

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14 BRITISH DENTAL JOURNAL VOLUME 220 NO. 1 JAN 15 2016

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