Keratin-based protection of enamel against acid-erosion

Enamel erosion is a prevalent and growing oral health concern, affecting approximately 20%-45% of the adult population, with incidence expected to increase. Current preventative strategies rely predominantly on fluoride-based interventions, which, while effective, are not without limitations, particularly in the context of erosive challenges. Consequently, there is an increasing interest in alternative or adjunctive approaches for protecting enamel against acid-induced damage. This study investigated the protective potential of a keratin-based surface treatment against acid-induced enamel erosion and compared its performance with sodium fluoride at clinically relevant concentrations. Enamel specimens from extracted human molars were treated with keratin, sodium fluoride (1,450, 5,000, or 22,600 ppm), artificial saliva, or deionised water, and subsequently exposed to citric or hydrochloric acid under in vitro conditions. Enamel surface microhardness, surface profilometry, and scanning electron microscopy were used to assess hardness retention, surface loss, and morphological changes. Following acid exposure, keratin-treated specimens exhibited greater hardness retention than control groups and lower fluoride concentrations under both erosion models, with performance approaching that observed in the 22,600 ppm fluoride group. Profilometric analysis indicated reduced surface loss in treated groups relative to controls, although differences were not statistically significant. SEM observations supported these findings, demonstrating improved preservation of surface and subsurface enamel structure in keratin- and high-fluoride-treated samples. Within the limitations of this in vitro study, keratin demonstrated consistent protective effects against enamel erosion, supporting further investigation as a potential biomaterial for erosion prevention under clinically relevant conditions.