The effects of acid-etching on enamel from different clinical variants of amelogenesis imperfecta: an SEM study

Successful bonding of resins to teeth affected by amelogenesis imperfecta (AI) may be highly dependent on how the enamel responds to acid etching. The aim of this study was to determine, using scanning electron microscopy (SEM), the types of etching pattern achieved with 37% phosphoric acid on dental enamel of 5 clinical variants of AI, namely, pitted hypoplastic, smooth hypoplastic, X-linked (male), X-linked (female), and hypomineralized.

A normal premolar and primary molar from two healthy patients were used as controls. The enamel was scanned before and after acid etching for 1 min. In the normal, control teeth, the three classical etching patterns were produced: type 1, in which the prism cores are preferentially removed; type 2, in which the prism peripheries are removed, and type 3 in which the removal of enamel does not relate to prism structure.

In the normal primary molar, patterns of types 2 and 3 were generally produced. In the AI teeth, the effects of acid etching reflected the clinical variant of AI. All three etch patterns were observed in the enamel surrounding the pits in the pitted type of AI and in the bands of normal enamel in the female with X-linked AI, as well as in the hypomineralized variant. In contrast, no typical etch patterns could be detected in the enamel from the male patient with X-linked variant, as well as from the enamel affected by the smooth hypoplastic variant.

The lack of typical etching patterns in these variants may be the result of abnormal prism structure, or the standard etching time and/or acid concentration may be inappropriate for the abnormal enamel. The results of this study may have useful applications in the restoration of teeth affected by AI.