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
A 37 year old female patient complains of discoloration with her upper front teeth. Intra-oral examination reveals Intrinsic staining with maxillary incisors. Dentist prepares teeth to receive direct composite veeners. Which of the following  instrument material cannot be used in this case ? 
Select and explain. 
A. Stainless steel, B. Teflon, C. Teflon coated metal, D. Non metallic
A: Stainless steel
Answer: A: Stainless steel 
Explanation: None