What primary oral fluid acts to buffer acids and enable remineralization?

• A. Saliva
• B. Blood serum
• C. Urine
• D. Lymph

Answer: (A)

Saliva is the primary oral fluid that buffers acids and enables remineralization. It contains bicarbonate and phosphate that neutralize acids produced by plaque bacteria, helping to keep the dental environment at a pH that limits mineral loss. At the same time, saliva delivers calcium and phosphate ions to the tooth surface, creating the conditions for minerals to redeposit into demineralized enamel—reversing early lesions. Fluoride in saliva from toothpaste or water further enhances this process by forming a more acid-resistant fluorapatite.

The effectiveness depends on how well saliva flows: stimulated, adequate flow provides more buffering capacity, more ion availability, and faster removal of food debris. When salivary flow is low, protection diminishes, increasing caries risk. Other fluids like blood serum, urine, or lymph don’t bathe the teeth with the same locally available buffering system and mineral ions, so they don’t support remineralization in the mouth the way saliva does.