Oral bacteria, besides S. mutans, can be sensitive to the presence of hydrogen peroxide through generation of _________.

• A. Hydrogen radicals
• B. Reactive oxygen species
• C. Hydroxy radicals
• D. Atomic oxygen radicals

Answer: (B)

Hydrogen peroxide can create a range of damaging oxidative molecules inside bacteria, known as reactive oxygen species. When H2O2 is present, it can lead to the formation of species like superoxide, hydroxyl radicals, and singlet oxygen through catalytic reactions. These reactive oxygen species attack essential cellular components—proteins, lipids, and DNA—causing oxidative stress and potentially killing the bacteria. That broad concept—reactive oxygen species—best captures the mechanism by which hydrogen peroxide exerts antimicrobial effects in oral bacteria. While specific radicals like hydroxyl radicals are part of ROS, the general term ROS covers the whole group of reactive molecules produced from H2O2, making it the most accurate choice.