The Universal (Tofflemire) matrix system is used in Class II restorations. The primary function of the matrix is to restore anatomic proximal contours and contact areas. A properly placed matrix should:
* Be rigid against the existing tooth structure
* Establish proper anatomic contour
* Restore correct proximal contact relation
* Prevent gingival overhang
* Be able to be easily removed
Armamentarium
Tofflemire Matrix Retainer
Matrix bands
(narrow or wide; usage depends on depth of gingival cavosurface margin)
Wedges
Cotton Pliers
Scissors
Knife
The matrix retainer has four parts:
1. Head – U-shaped, has three guides, or slots, for the position of the band
2. Locking vise – sliding body that holds the band
3. Long knob – changes the diameter of the loop
4. Short knob – locks the band in place within the sliding body
Matrix Retainer Video Demo
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Procedure
1. Try the wedge.
2. Burnish the matrix band.
3. Place the matrix band into the retainer.
4. Fit the matrix onto the tooth.
5. Place the wedge.
6. Tighten the matrix band around the tooth.
Try the wedge.
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Use of a wedge with the matrix band serves two purposes:
1. Helps to compress the matrix band against the tooth structure to create a tighter seal, preventing gingival overhang.
2. Provides slight separation between the teeth, compensating for the thickness of the matrix band, and thus helping to create a tight contact between the finished restoration and the adjacent tooth (otherwise, when matrix band is removed, a space equaling the thickness of the matrix band would exist between the restored proximal surface and the adjacent tooth).
Prior to placing the matrix band, place a wedge in the gingival embrasure to check the relationship between the occlusal surface of the wedge and the gingival cavosurface margin. In order for a wedge to be effective during amalgam placement, it should fit tightly against the tooth and its occlusal surface should extend above the gingival cavosurface margin, creating a tight seal.
To place the wedge, stretch the rubber dam tightly to allow it to seat more gingivally and keep it from getting caught by the wedge. After placing the wedge, use the blunt end of the cotton pliers to push it into place.
If the wedge fits tightly against only a portion of the gingival proximal surface, fit a slightly larger wedge and use a knife to contour the side of the wedge facing the proximal surface, so that it fits snugly around the entire gingival proximal surface. For example, this contouring of the wedge is often required when restoring the mesial surface of the maxillary first premolar, due to the mesial concavity that exists in its cervical portion.
If the wedge fits tightly against the tooth but it’s occlusal surface is too high above the gingival cavosurface margin, a knife can again be used the trim the occlusal surface of the wedge so that it extends just above the gingival cavosurface margin.
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