Which type of protection is not provided by a liner?

• A. Electrical protection
• B. Thermal protection
• C. Pulpal protection
• D. Bacterial infection protection

Answer: (D)

Liners are placed to shield the pulp from irritants and to reduce the effects of heat and chemical exposure from the cavity preparation and restorative materials. They create a thin protective layer over the dentin, help buffer chemical irritation, and can even stimulate dentin formation with certain materials. However, they are not reliable barriers against bacterial infection. Protecting the pulp from bacteria depends primarily on obtaining a tight, well-sealed restoration and minimizing microleakage; the liner itself doesn’t provide long-term antibacterial protection. Some liners may have modest antibacterial properties due to their composition, but that is not their main or guaranteed role, whereas pulpal and thermal protection are the core functions.