The availability of which ions can be the limiting factor for net enamel remineralization to occur?

• A. Fluoride Ions
• B. Calcium Ions
• C. Calcium and Phosphate Ions
• D. Phosphate Ions

Answer: (C)

Net enamel remineralization depends on the availability of mineral ions in saliva. Calcium and phosphate provide the building blocks to reform the mineral phase of enamel, forming hydroxyapatite or fluorapatite when fluoride is present. If these ions are readily available and the environment allows remineralization (saturation of saliva with calcium and phosphate, appropriate pH), minerals can be redeposited into demineralized areas. If either calcium or phosphate is in short supply, remineralization cannot proceed efficiently, so net remineralization is limited. Fluoride enhances the process by stabilizing the newly formed mineral and making it more acid-resistant, but it cannot compensate for a lack of calcium or phosphate. Therefore, the availability of calcium and phosphate ions is the limiting factor for net enamel remineralization.