Which one of the following hand instruments is usually used to adapt a filling material to the cavity margins to avoid leakage under the set restoration?

The burnisher is the appropriate hand instrument used to adapt a filling material to the cavity margins, ensuring a smooth finish and helping to prevent any potential leakage under the set restoration. When a filling is placed in a cavity, it’s crucial that it fits snugly against the walls of the preparation. The burnisher, with its smooth and rounded edges, effectively compresses and shapes the restoration material, enhancing the seal between the filling and the tooth structure. This is vital for maintaining the integrity of the restoration and reducing the risk of postoperative sensitivity or decay.

Additionally, its ability to polish the surface of the material contributes to a smoother finish, which can also aid in reducing plaque accumulation around the restoration. While other instruments serve different purposes in dental procedures—like the amalgam plugger primarily for packing amalgam into the cavity or the spoon excavator for removing carious dentin—the burnisher is specifically designed for the effective adaptation and finishing of restorative materials.