Effect of pH, concentration, and treatment time of aluminum solutions on acid dissolution of enamel

Dissolution tests were conducted with human enamel following treatment with aqueous aluminum (Al) solutions under conditions of varying pH, concentration, and treatment time. Al reduced enamel dissolution in a pH 4 acetate buffer most effectively when used in the pH range of 3 to 4, at concentrations above 0.005 mol/L, and for treatment times of more than four minutes. However, significant activity was observed with concentrations as low as 0.0005 mol/L Al and treatment times as short as 15 seconds. The effects of Al solution pH and concentration on enamel dissolution were related to the hydrolysis of Al above pH 4 and to the accelerated dissolution of apatite below pH 3.