Martensitic stainless steel
Most reusable dental hand instruments are made from this family of steels. Here is why.
What "martensitic" means
Martensitic stainless steels can be hardened by heat treatment, unlike the austenitic grades used for sinks and food equipment. That property is what lets a scaler hold an edge and forceps beaks keep their shape under load.
The two common grades
| Grade | Chromium | Carbon | Typical role |
|---|---|---|---|
| AISI 410 | 11.5–13.5% | up to 0.15% | Tougher parts that must flex: handles, pliers, retractors |
| AISI 420 | 12–14% | 0.15% and above | Harder parts: cutting edges, beaks, tips |
These grades appear in ISO 7153-1 and ASTM F899, which list steels used for surgical instruments. Our instruments use premium surgical-grade stainless steel from these two grades.
Hardening and tempering
The steel is heated until its carbon dissolves, cooled rapidly to form hard martensite, then reheated at a lower temperature to restore toughness. Getting that balance right decides whether a tip chips, bends or holds.
Passivation
Chromium in the steel forms a very thin oxide film that protects the surface. Passivation is a chemical treatment, usually with nitric or citric acid, that removes free iron and surface contamination left by machining and polishing so that film forms evenly. Correct cleaning and drying help keep it intact in use.
What attacks it
- Chlorides: dried blood, saline and some detergents
- Moisture left on instruments after the cycle
- Contact with rusting or damaged instruments in the same load
- Hard or mineral-rich rinse water