Which of the following cannot be disinfected?

Emery boards are designed for single-use and are typically made of porous materials, which makes them difficult to clean and disinfect effectively. Because they cannot be fully sanitized and can harbor bacteria or other pathogens after use, they should be discarded after a single treatment rather than being disinfected for reuse.

On the other hand, glass files, metal tools, and plastic utensils are made from materials that can withstand disinfection processes. Glass files and metal tools can be sterilized through autoclaving or soaking in appropriate disinfectants, while plastic utensils may be disinfected using various methods, provided they are not damaged during the process. Therefore, it is the emery board's composition and intended use that makes it unsuitable for disinfection and reuse.