Spot welded matrix

Matrix
Dr. Aly Sharaf

Matrix is required for restoring a class II cavity
Criteria:
- Rigid
- Stable
- Well contoured
- Will not dislodge under force of
condensation
- No escape of material
Dr. Aly Sharaf

Types
Commonly used in primary dentition
especially when several restorations
are done in same appointment
• Spot welded matrix
• T – band matrix
Dr. Aly Sharaf

Spot welded matrix
Armamentarium
• Matrix band material, 5 mm (3/16”) wide, 0.0505
mm (0.002
002”) thick
• Small wooden wedge or preformed anatomic
wedge
• Flat nose, serrated pliers (e.g. #102
or # 110)
• Contouring pliers (ball and socket)
• Crown and bridge curved scissors
• Explorer
• Dental mirror
• Plastic instrument or spoon excavator
Dr. Aly Sharaf

Spot welded matrix
1. Cut a matrix and spot
weld ends
• Cut 5 cm long
• Form a drop shape loop,
then hold the
joined ends together
between the electrodes of
the spot welder (low
energy, 1 – 3). Allow 2 mm
of material extended
beyond.
Dr. Aly Sharaf

2. Adapt matrix to tooth
• Seat band 0.5 – 1.0 mm gingivally
i and occlusally
• Grasp end with flat nose serrated
pliers
Dr. Aly Sharaf

3. Contour proximal portion of
band (if needed)
Dr. Aly Sharaf

4. Spot weld the matrix band at the
crease and trim the ends
• Hold the end of the band tight with the
pliers and remove the band from the
tooth.
• Spot weld the band (energy level at 1-
3) in the center next to the crease.
• Trim the ends with a scissors to 3-4 mm
long
• Flatten the end of the band back
against the tooth
Dr. Aly Sharaf

5. Reseat the band on the tooth and
wedge it
• Replace the band on the tooth, it
should fit tightly and extend 0.5 mm to
1.0 mm both gingivally beyond the
gingival margin and occlusally beyond
the marginal ridge.
• Select a small wedge (trim if needed
using scalpel or sharp knife-edged
instrument) and insert it from the the
larger embrasure
Dr. Aly Sharaf

6. Removing the spot-Welded matrix
Break the joint after removing gross
amalgam excess from proximal area and
forming the marginal ridge but before
the carving
7. Complete the restorative procedure
Dr. Aly Sharaf

T - Band matrix
• Easy placement, contouring and removal
• Narrow or wide
• Curved or straight
• Brass or stainless steel
(stainless steel has more body making it
easier to condenses forcefully against the
band)
Dr. Aly Sharaf

• Shape
the T band
into a circle
and
adjust it
to a size
slightly smaller than
the tooth
Dr. Aly Sharaf

• Bend the wings of the T-band with a
plier.
• Shift the beaks of the pliers to the long
end of the band and pull them along the
band (like a paper ribbon)
• Shape the T-band into a circle in the
direction of the curl
• Slip the end of the band between the
bent wings and adjust it to a size
slightly smaller than the tooth.
Dr. Aly Sharaf

• Adjust the matrix to the tooth
• Keep sliding joint of the matrix on the buccal and the
long end toward the mesial. It should extend 0.5-1.0
mm past cavo-surface margin
• Stabilize the joint with fingers and pull the long end
to tighten the band on the tooth.
• Fold the tab distally back over the joint
• Remove the band for further adustments
Dr. Aly Sharaf

Dr. Aly Sharaf

Trim the matrix band to size
• Remove the band and flatten the
fold with pliers against the wings
• Cut the tab even with thte ends of
the wings and round the corners
Dr. Aly Sharaf

Reseat the matrix band and
wedge it.
• Replace the band on tooth
with the trimmed end directed
distally, it should be snuggly
fittingi
• Wedge the tooth
Dr. Aly Sharaf

REMOVING THE T-BAND
• Open the joint
• Remove the matrix
Dr. Aly Sharaf

Open the joint
After removing amalgam excess, and
before carving open the joint with
excavator or plastic instrument by
raising i the tab
Dr. Aly Sharaf

Remove the matrix
• Remove wedge
• Secure the marginal ridge area
• Either
cut
band
close
restoration and pull it out or
• Gently rock band occlusally
ll
to
Complete restorative procedure
Dr. Aly Sharaf

WEDGES
Must be always used except when there is a
diastema or a missing adjacent tooth
• Allow the band to withstand the pressure
of condensation and prevent flash on
gingival margin
• Provide slight separation between teeth
Dr. Aly Sharaf

WEDGES
Types
• Triangular
• Anatomically shaped
Dr. Aly Sharaf