Which method requires the longest time for sterilization?

The dry heat oven method is known for requiring a longer time for sterilization compared to the other methods listed. This process relies on high temperatures to sterilize instruments, typically reaching around 320°F (160°C) for 120 minutes or longer, depending on the load and type of instruments being sterilized.

In contrast, steam under pressure, or autoclaving, uses saturated steam to quickly achieve sterilization, generally taking around 15-30 minutes. Chemical vapor sterilization combines chemicals and heat, offering effective results in a much shorter time frame, typically within 20 minutes. Manual scrubbing, while important for cleaning instruments, does not actually provide sterilization, but rather prepares instruments for further sterilization methods.

Therefore, the longer exposure time and higher temperatures required for dry heat sterilization make it the method that takes the most time to achieve effective sterilization, emphasizing the importance of understanding the nuances between various sterilization techniques in dental hygiene practice.