The correct formulation of 18% chromium and 8% nickel corresponds to stainless steel commonly used in orthodontic wires. Chromium at 18% provides excellent corrosion resistance, essential for the oral environment. Nickel at 8% enhances the wire’s flexibility and strength, critical for effective tooth movement. This balance maintains biocompatibility while ensuring mechanical properties necessary for orthodontic treatment. Lower percentages reduce corrosion resistance and mechanical performance, while higher percentages may alter these key characteristics adversely. Therefore, the 18/8 ratio is the standard for durability and clinical effectiveness in orthodontics.

Reference: Graber's Orthodontics, 7th Edition.