These are steel matrices designed to reduce the space occupied by the matrix. For this purpose, OptraMatrix features selectively thinner contact areas and an opening (window) on the side opposite to the involved area. This way, the space occupied by the matrix is minimized, achieving firm and sealed contact areas. OptraMatrix is available in six different versions, with a mesial variant (MO restorations), a distal variant (OD restorations), and a three-surface variant (MOD restorations) for both posterior and premolar teeth. In addition to the selectively thinned area, the mesial and distal versions also feature an opening for contact on the side of the cavity that is not involved.