Best method for sterilizing complex instruments and delicate materials:
Ethylene oxide sterilization is the best method for sterilizing complex instruments and delicate materials.
Porous and plastic materials absorb the gas and require aeration for 24 hours or more before it is safe for them to contact skin or tissues.
Units with large chamber sizes hold more instruments or packs per cycle; however, they are very expensive.
Some chamber designs or sizes are better suited to accept stacks of instrument trays. Manufacturers should be consulted to obtain detailed information about these sterilizers.

Sturdevants operative dentistry 4th edition page 374.
Sunlight sterilization
Dry heat sterilization
Ethylene oxide sterilization
Chemiclave