Which of the following is not true regarding a properly assembled matrix retainer and band for an amalgam restoration?

The choice stating that the band extends 1.5 to 2.5mm gingival to the cavosurface is not true regarding the proper assembly of a matrix retainer and band for an amalgam restoration. In a correctly assembled matrix band, the band should actually extend a very minimal distance below the cavosurface margin, specifically around 0.5 to 1.5mm, not 1.5 to 2.5mm. This design is crucial because it ensures an optimal seal and support for the amalgam material while allowing for proper contours in the final restoration.

The alternative aspects about the assembly detail important orientations that promote correct placement. The narrower loop of the band is designed to face gingivally, allowing it to conform to the contour of the tooth and maintain a proper fit. Furthermore, the retainer's slot openings are designed to face gingivally as well, enhancing the ease of placement and adjustment during the procedure. Lastly, setting the band at the appropriate height—close to the occlusal plane, up to 1.5mm occlusal to it—is vital for the restoration's strength and function. These factors together contribute to the success and longevity of the amalgam restoration.