What polishing agent is recommended when polishing porcelain restorations?

Aluminum oxide is the recommended polishing agent for porcelain restorations due to its effective abrasive properties that can provide a smooth finish without damaging the surface of the porcelain. It has a grit that is suitable for polishing, allowing for the enhancement of the aesthetic qualities of the restoration, such as shine and smoothness, without compromising its integrity.

Aluminum oxide is specifically chosen because it does not leave behind scratches that can be seen on the porcelain's surface, maintaining both the appearance and function of the restoration. Its durability ensures that it can withstand the mechanical forces during the polishing process, leading to a superior final product.

In contrast, other materials such as diamond paste, while very effective for other materials, may be too aggressive for porcelain and could lead to unwanted surface damage or alter the finish. Silicon carbide, although a common abrasive in other contexts, is not as suitable for porcelain because it can create rough surfaces. Calcium carbonate, on the other hand, is typically used for polishing softer materials and would not provide the necessary refinement for porcelain restorations.