This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Cutting edges of the orthodontic instruments are made up of 
Select and explain. 
A. Austenitic carbon steel, B. Martensitic carbon steel, C. Ferritic carbon steel, D. Cementite carbon steel
B: Martensitic carbon steel
Answer: B: Martensitic carbon steel 
Explanation: Because of their high yield strength and hardness, martensitic stainless steels are used for surgical and cutting instruments. 
The austenitic stainless steels are the most corrosion-resistant of the three major types and are the stainless steels used for orthodontic wires, endodontic instruments, and crowns in pediatric dentistry.
Ferritic Stainless Steels: These alloys provide good corrosion resistance at a low cost, when high strength is not required. They cannot be hardened by heat treatment or readily work-hardened. Consequently, they have little application in dentistry.
Ref: Phillip’s 12th edition page 406