Etching time in teeth with fluorosis

Generally, a 20 second time is recommended. Enamel rich with Flourohydroxy apatite may be resistant to etching and may need to be exposed for longer periods. Etching time for enamel varies depending on the type and quality of enamel. Generally, a 15 sec etching with 30 to 40% phosphoric acid is sufficient to reach the characteristic clinical endpoint of a frosty enamel appearance. Deciduous enamel generally contains same prismless enamel that has not yet worn away and requires longer etching time (20-30sec) to create a etched pattern. 5-40% phosphoric acid recommends longer etching times for primary teeth, approximately 30sec.