Abdulaziz Al-Abdulwahed, BDS

Definition  Something within or from which something else originates, develops, or takes form.  Mold.  Die.  A material in which something is enclosed or embedded (as for protection or study).  Merriam-Webster dictionary  Your dictionary. com

The purpose  Confine the amalgam so that adequate condensation forces can be applied.  Allow reestablishment of contact with the adjacent tooth.  Resist extrusion of the amalgam and the formation of an overhang.  Provide for adequate contour of the proximal surface of the restoration.  Establish an acceptable surface texture to the proximal surfaces, especially to the area that cannot be carved and burnished.

Qualities of a good matrix  Rigidity.  Establishment of proper anatomic contour.  Restoration of correct proximal relation.  Prevention of gingival access (marginal overhang).  Convenient application.  Ease of removal.

Types of Matrices  Universal Matrix (Tofflemire):  Indicated ideally for MOD, or lingual surface preparation.  Can be placed in a facial or lingual in relation to the tooth.  The Tofflemire retainer consists of different parts:  Head.  Slide.  Rotating spindle.  Set-screw. Used with most restoration materials.

Types of Matrices  Precontoured bands. Precontoured Tofflemire band. Palodent.  Limited application, due to very rounded contour.  More suitable in distal of max. canines, and man. 1 st premolars.  The contact area of the adjacent tooth is occasionally too close to allow placement of the band without making a dent on the contact area making it unusable.

Types of Matrices  Automatrix. 4 different bands: Narrow regular, Wide regular, Medium regular, Medium thin. Indicated to be used with extensive CL II, involving two or more cusps. Auto-lock loop can be positioned either facially or lingualy. Difficult to establish a proper anatomic contour, since it wasn’t precontoured in the beginning.

Other types  Omni-matrix: preassembled Tofflemire, intended for a one time use then disposal.  Matrix strips: Dead soft, metal. Plastic strip. (CL lll, CL IV).  Most matrices either comes in metal (steel), clear (plastic).  Copper band matrix: used in complex amalgam restorations, rigid, recontourable, festooned.

Wedging  Wedging is an integral, and a crucial part of the placement of the matrix.  Used to stabilize the matrix in place, and to prevent the excess of amalgam (marginal overhang).  Fundamental to retract the rubber dam in a gingival direction.  Wedges can be: Wooden. Clear (plastic). Wizard wedge, triangular cross-section. Rounded wedges. Premier Sycamore wedges.

Required Reading  Sturdevant’s Art & Science Of Operative Dentistry, 4 th ed. Pages: ; ; ; ;  Fundamentals Of Operative Dentistry, A Contemporary Approach, Richard S. Schwartz, 2 nd ed. Pages: ; ;