effect of nano-hydroxyapatite incorporation on the immediate and long-term bond stability of a one-step self-etch adhesive

Objective: this study evaluated the effect of incorporating nano-hydroxyapatite (nhap) at various concentrations on the immediate and long-term bond strength of a one-step self-etch adhesive to dentin.methods: a total of 100 sound maxillary central incisors were collected. the dentin was exposed on the labial surfaces, and the teeth were randomly assigned into two groups (n=50) based on the evaluation time points: 24 hours and 6 months. each group was further divided into five subgroups (n=10) based on the concentration of nhap (0, 1, 2, 3, and 4 wt%) incorporated into adper single bond universal adhesive. composite resin buildups were formed on dentin using cylindrical molds, and light-cured. shear bond strength (sbs) was measured by a universal testing machine, and fracture modes were assessed under a stereomicroscope. statistical analysis was performed using a two-way anova (p<0.05).results: at 24 hours, the highest bond strength was observed in 2% nhap (41.68 ± 15.24 mpa), followed by 1% nhap (36.75 ± 14.24 mpa), both significantly greater than the control group (0% nhap: 17.03 ± 4.57 mpa; p < 0.05). after 6 months, 2% nhap again demonstrated the highest bond strength (43.28 ± 6.87 mpa), followed by 1% nhap (37.00 ± 6.90 mpa), both significantly higher than the control (15.28 ± 4.63) and 4% nhap groups (14.58 ± 2.33 mpa; p<0.05).conclusions: the incorporation of nano-hydroxyapatite at concentrations up to 2 wt% into a one-step self-etch adhesive significantly enhanced both immediate and long-term bond strength to dentin.