THE EFFECT OF NANOHYDROXYAPATITE-CONTAINING TOOTHPASTE ON THE PREVENTION OF ENAMEL EROSION: AN IN VITRO PILOT STUDY

Abstract

Dental erosion from gastroesophageal reflux disease (GERD) poses a significant clinical challenge, as chronic exposure to gastric acid (pH 1.0-1.5) leads to progressive and irreversible enamel loss. While stannous fluoride (SnF₂) is well-established for erosion prevention, nanohydroxyapatite (nano-HAP) has emerged as a biomimetic alternative; however, evidence for its efficacy under severe, repeated acid conditions remains limited. This study aimed to compare the protective effects of nano-HAP-containing toothpastes against simulated gastric acid erosion in laboratory setting. Eighteen enamel specimens from extracted permanent molars were randomly allocated into three groups: nano-HAP-containing toothpaste (Group A), SnF₂-containing toothpaste (Group B) and non-fluoride toothpaste as negative control (Group C). Specimens underwent a five-day cycling protocol of three daily hydrochloric acid challenges (0.01 M, pH 2.2) interspersed with toothpaste treatments. Outcomes were assessed by Knoop surface microhardness (percentage surface hardness change, %SHC) and non-contact profilometry (enamel surface loss). All groups showed significant reductions in surface microhardness following erosive cycling. Group A demonstrated significantly lower %SHC than the negative control (p = 0.034), whereas Group B was not significantly different from either Group A or C (p = 0.212, 0.576, respectively). Enamel surface loss did not differ significantly among all groups (p = 0.263). Based on these findings, nano-HAP-containing toothpaste partially preserved enamel surface hardness under simulated GERD conditions but did not significantly reduce bulk enamel loss. These findings suggest that nano-HAP provides limited protection against severe, repetitive acid exposure, and further studies should explore combinations with fluoride or other bioactive agents to enhance anti-erosive efficacy.

Keywords: Hydroxyapatite, Tooth Erosion, Gastroesophageal Reflux, Tin Fluorides, Toothpastes