During assembly of the matrix into the Tofflemire, which way should it be oriented for the upper left quadrant?

The correct orientation of the matrix when assembling it into the Tofflemire retainer for the upper left quadrant is to the left. The reason for this is that the matrix band needs to be positioned in such a way that it properly conforms to the shape of the tooth being restored and allows for adequate contact with adjacent teeth. For the upper left quadrant, angling the band to the left ensures that the band effectively captures the anatomy of the tooth and aids in the proper contouring of the filling material being placed.

When the matrix is correctly oriented, it allows for a smooth restoration process, ensuring that the dental material will fill the cavity appropriately and that there is sufficient support for the material until it sets. This positioning also helps to prevent materials from spilling out and supports better isolation and visibility during the procedure.