Which of the following is a common method to sterilize dental instruments?

Steam under pressure is the correct method for sterilizing dental instruments because it effectively kills all microorganisms, including spores, through a combination of heat and moisture. This process, known as autoclaving, utilizes saturated steam under pressure, which raises the temperature beyond that of boiling water, usually to around 121-134 degrees Celsius. The pressurized steam penetrates instruments and materials, ensuring thorough sterilization.

Boiling water is not an effective method for sterilization because, while it can reduce the number of microorganisms, it does not achieve the high temperatures required for complete destruction of resistant spores. Ethylene oxide gas is indeed used for sterilization, particularly for heat-sensitive instruments, but it requires specific handling due to its toxicity and flammability. Radiation sterilization is also a valid technique, primarily used in industrial settings, but it is less common in dental practices compared to steam under pressure, which is widely accessible and efficient for most dental instruments.