Applies and Removes Matrix System and Wedges
Rebuilding the missing wall
A matrix substitutes for a missing proximal wall during restorative treatment. It holds material, restores contour, and prevents overhangs. Wedges separate teeth slightly and adapt the matrix to the gingival margin.
Concepts to know
- Types: circumferential (Tofflemire-style) for posterior Class II, sectional matrices for tighter contacts, and clear matrices for light-cured materials because they transmit curing light.
- Placement: select the correct band size, assemble the retainer, seat the band with the smaller opening toward the gingiva, tighten, then place the wedge from the lingual or buccal as access allows.
- Wedging: the wedge goes into the embrasure to adapt the band and slightly separate teeth, compensating for band thickness so the contact is not left open.
- Removal: remove the wedge, loosen the retainer, and remove the band carefully to avoid chipping the new restoration.
- Curing: clear matrices allow light penetration; metal matrices block light and require careful technique.
Traps
Questions love the direction of the band opening and the purpose of the wedge. The wedge is not just to hold the band; it compensates for band thickness so the contact is correct. Another trap is using a metal matrix with a light-cured material and expecting adequate cure through it.
Rule of thumb
Wedge adapts and separates; matrix contours and contains. If an answer describes a wedge as merely a retainer, it is incomplete.