National Dental Hygiene Certification Exam (NDHCE) Practice

The concentration of alcohol considered effective for disinfection is 75%. This is due to the fact that at this concentration, alcohol has optimal antimicrobial properties. A 75% alcohol solution can quickly denature proteins and disrupt the cell membranes of bacteria and viruses, leading to effective microbial kill. Concentrations that are too low, such as 50%, do not provide sufficient efficacy for disinfection, as they may not fully denature proteins or penetrate the cell wall of microorganisms effectively. Higher concentrations, like 90%, can be less effective because they evaporate too quickly and may not remain in contact with the microbes long enough to achieve their disinfectant action. Additionally, pure alcohol can lead to the formation of a protective layer on the microorganisms, which could hinder the disinfection process. Therefore, 75% alcohol strikes the right balance between efficacy and contact time, making it the preferred concentration for disinfection purposes.