Dental Matrices

Definition and Importance of Matrices

• A matrix is a metal or non-metal piece used to support and give form to a restoration during its packing and hardening.
• Matrices serve as a temporary wall during condensation of restorative material, give shape and contour to the restoration, and maintain the form until hardening.
• They also keep gingival tissues and the rubber dam away from the cavity margins during procedures.

Requirements of Matrices

• Easy to adapt to teeth
• Rigid enough to resist condensation pressure
• Compatible with the restorative material
• Smooth and highly polished
• Easy to contour
• Easy to introduce and remove
• Thin enough to not interfere with the tightness of contact

Types of Matrices

• Patented matrices: ready-made matrices, such as Ivory Matrix Holder No.1 and Universal (Tofflemire) Matrix System
• Non-patented matrices: specially constructed matrices, such as wedged matrix, compound wedged matrix, and window matrix

Patented Matrices

• Ivory Matrix Holder No.1: provides one proximal wall, used in compound class II cavity preparation
• Universal (Tofflemire) Matrix System: indicated for compound or complex Class II restoration, provides good stability, anatomic adaptation, and ease of insertion and removal

Matrix Bands

• Made of flexible stainless steel
• Available in 2 thicknesses: 0.0015 and 0.002 inch
• Available in various occluso-gingival widths
• Can be burnished to deform and smooth the band contour

Rules of Application for Matrix Bands

• 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
• The matrix band is placed in the slotted side of the retainer gingivally
• The straight retainer is placed on the buccal side
• The loop of the band can be placed centralized, from right, or from left depending on the location of the tooth

Non-Patented Matrices

• Wedged Matrix: a piece of well-contoured band material is cut to slightly extend past the cavity margins buccally and lingually and then stabilized in place by means of a wooden wedge
• Compound Wedged Matrix: similar to the wedged matrix, but with further stabilization using modeling compound
• Window Matrix: a universal matrix with a custom-made trapezoidal hole related to the position of Class V, suitable for wide Class V cavities with amalgam restoration

Advantages of Non-Patented Matrices

• Provides better contact and contour in restoring Class II tooth preparation
• Adequate rigid and stable than other matrix systems
• Easy to remove
• Little proximal carving is required
• Recontouring can be easily done after compound placement

Disadvantages of Non-Patented Matrices

• Time-consuming

Dental Wedges

• Devices that stabilize the matrix band in place during condensation and hardening of the restorative material, preventing marginal overhangs, and maintaining adequate teeth separation
• Types of dental wedges: wooden wedges and plastic wedges

Wooden Wedges

• Made of orange wood, absorbs saliva and increases in size
• Provides more stabilization to the matrix band with adequate temporary separation of adjacent teeth
• Can be rounded, triangular, or anatomical
• Color-coded and has different sizes

Plastic Wedges

• Similar to wooden wedges but made of plastic
• Color-coded

Placement of Wedges

• Length of the wedge should be in the range of 1-1.2 cm
• Should not irritate tongue, cheek, and gingival tissue
• Wedge should be inserted beneath the contact area in the gingival embrasure
• Usually inserted from the lingual embrasure area as it is wider than the buccal area

Modified Wedging Techniques

• Double Wedging: 2 wedges are used, one is inserted from the buccal embrasure and another is inserted from the lingual embrasure; indicated in spacing between adjacent teeth where single wedge is not sufficient, and widening of proximal box in bucco-lingual dimension
• Wedge Wedging: 2 wedges are used, one wedge is inserted from the lingual embrasure area while another is inserted between the wedge and matrix band at right angle to the first wedge; indicated in treating mesial aspect of maxillary first premolar
• Piggyback Wedging: 2 wedges are used, one (larger) wedge is inserted as used normally, while the other smaller wedge (piggyback) is inserted above the larger one; indicated in cases of shallow proximal box with gingival recession, and provides closer adaptation and contour of the matrix band