The retention of sealants is achieved by etching the enamel with what substance?

The correct answer is phosphoric acid because it is commonly used in dentistry for etching enamel prior to the application of sealants and other restorative materials. Etching with phosphoric acid creates micro-roughness on the enamel surface, which enhances the bond strength between the tooth and the sealant material. This increased surface area allows the sealant to penetrate the microscopic irregularities of the enamel, resulting in a stronger adhesion and improved retention of the sealant.

Other acids, such as hydrochloric, citric, and sulfuric acid, do not serve the same purpose for dental applications. Hydrochloric acid is highly corrosive and could damage the enamel beyond what is desirable. Citric acid may alter the surface properties in a way that is not conducive to sealant retention, while sulfuric acid's strong oxidizing properties could severely compromise tooth structure. Thus, phosphoric acid is the preferred choice for effectively preparing enamel for sealant application.