Laser irradiation of dental hard tissues modifies the calcium to phosphate ratio, reduces the carbonate to phosphorous ratio, and leads to the formation of more stable and less acid soluble compounds, making the tooth less susceptible to acid dissolution. This statement is:

• A. False
• B. True
• C. Not proven
• D. Unrelated

Answer: (B)

Laser irradiation of dental hard tissues can cause surface modifications that increase resistance to acid attack. Enamel is largely hydroxyapatite with carbonate substituting for phosphate; carbonate-rich apatite dissolves more easily in acid. The laser’s photothermal energy dehydrates and can melt and then recrystallize the surface, forming larger, more ordered crystals with a Ca/P ratio closer to stoichiometric hydroxyapatite and with reduced carbonate content. This creates a more stable, less acid-soluble layer, making enamel less susceptible to acid dissolution. Although the exact effects depend on laser type and parameters, the described changes—altered Ca:P, reduced carbonate substitution, and formation of a more resistant phase—are consistent with laser-induced hard tissue modification. Therefore, the statement is true.