A comparative study of three etching solutions: effects on enamel surface and adhesive-enamel interface

Summary The chemical treatment of enamel surfaces is an approach in obtaining increased bonding of dental materials to tooth surfaces. Three etching solutions commonly used at present are 50% H3PO4, 50% H3PO4 attenuated with 7% zinc oxide and 50% citric acid. The effects of these three conditioning solutions on normal and polished enamel surfaces and on the interfaces between untreated enamel and etched enamel surfaces were studied by scanning electron microscopy. The variable etching pattern observed with each of the acids made a comparative study difficult. This was further complicated by the dependence of the etching action on prism orientation on polished enamel surfaces. Additional factors that have to be considered are the presence of prismless enamel and perikymata. Surface profile recordings of polished and acid-etched polished enamel surfaces provided some quantitative measure of the etching action of the conditioning solutions. The 50% citric acid solution had the mildest etching action while 50% H3PO4 and 50% H3PO4 attenuated with 7% zinc oxide elicited comparable responses.