Which of the following instruments are more efficient?
Stainless steel
Carbon steel
Both have equal efficacy
Carbon Steel

Carbon steel alloy contains 0.5 to 1.5 percent carbon in iron.
Instruments made from carbon steel are known for their hardness and sharpness.
Disadvantages with these instruments are their susceptibility to corrosion and fracture. They are of two types:

1. Soft steel: It contains <0.5% carbon
2. Hard steel: It contains 0.5 to 1.5% carbon
Stainless Steel

Stainless steel alloy contains 72 to 85 percent iron, 15 to 25 percent chromium and 1 to 2 percent carbon.
Instruments made from stainless steel remain shiny bright because of deposition of chromium oxide layer on the surface of the metal which reduces the tendency to tarnish and corrosion.
Problem with stainless steel instruments is that they tend to lose their sharpness with repeated use, so they need to be sharpened again and again.

​Nisha Garg, Amit Garg. Textbook of Operative Dentistry.  Edition 3. Page: 80