Which hand instrument is most likely used to place and contour composite filling material into an anterior tooth cavity?

The flat plastic is the most appropriate hand instrument for placing and contouring composite filling material into an anterior tooth cavity. This instrument is specifically designed with a flat, smooth surface that allows for precision in shaping and adapting composite materials to the contours of the tooth. It is particularly useful for achieving a smooth finish and properly contouring the restoration to match the natural anatomy of the tooth.

In contrast, the amalgam plugger is primarily used for packing and condensing amalgam material, which is denser and requires a different technique than the one used for composites. The ball-ended burnisher, while useful for smoothing restorations, is generally applied after placement for finishing touches rather than for initial placement and contouring. An excavator is designed for removing decay or debris from the cavity preparation and is not intended for placing or shaping filling materials.

Thus, the flat plastic stands out as the ideal tool for the specific task of working with composite filling materials in anterior teeth, making it the correct choice in this context.