Dry heat sterilization requires higher temperatures and longer exposure times compared to autoclaving, which uses moist heat and steam under pressure. This makes dry heat sterilization significantly more time consuming. While autoclaving typically sterilizes instruments in 15-30 minutes, dry heat methods may take 1-2 hours or longer to achieve equivalent microbial kill. The prolonged duration is due to the need for dry heat to penetrate and oxidize cellular components effectively without the aid of steam. Therefore, its main disadvantage compared to autoclaving is being time intensive, limiting its practical use in busy surgical settings.

Reference: Principles and Practice of Infectious Diseases, Mandell, Douglas, and Bennett, 9th Edition.