The correct answer is Gold.

- Among the dental restorative materials listed, gold demonstrates the highest resistance to corrosion in the oral environment.
- This is primarily due to its noble metal properties, meaning it is chemically inert and does not easily react with saliva, food acids, or other substances present in the mouth.
- Gold's excellent biocompatibility and chemical stability contribute to its long-lasting durability, making it an ideal material for crowns, inlays, and other restorations.

In contrast:
- Titanium is highly corrosion-resistant and is frequently used for dental implants, but it forms a protective oxide layer rather than being inherently inert like gold.
- Amalgam contains mercury and metals like silver and tin, which can undergo corrosion over time in the oral environment, leading to surface degradation.
- Stainless steel is resistant to corrosion but is less inert than gold, and it can corrode under certain acidic conditions in the mouth.

Therefore, due to its chemical inertness and noble metal characteristics, gold remains the gold standard for corrosion resistance in dental restorations.

Reference: Sturdevant's Art and Science of Operative Dentistry, 7th Edition, Volume 1, Chapter 10, Page 350