Does Hydroxyapatite Nanoparticles’ Addition Decrease Nanoleakage?

Objectives: To evaluate the efficiency of hydroxyapatite nanoparticles’ addition and thermocycling in preventing nanoleakage of class V restorations. Methods: Adper Single Bond 2 Total-Etch Adhesive (SB), 3M/ESPE, was used. Class V cavities were prepared (4mm length x2mm width x2mm depth) on buccal surfaces of 80 sound human premolars. Cavities were divided randomly into four groups (n=20), 1) bonded using SB (no nanoparticles were added), 2) nanoparticles dissolved in water and rubbed on the etched tooth substrates before bonding, 3) nanoparticles dissolved in ethanol and rubbed on the etched tooth substrates before bonding, and 4) nanoparticles dissolved in SB adhesive and rubbed on the etched tooth substrates. SB bonding agent applied to the second and third groups after nanoparticles’ application. All of the cavities were then restored using Z350 XT resin composite (3M/ESPE). Each group was then assigned into two subgroups (n=10), one of the subgroups was thermocycled (5-55°C) with 1 min dwell time for 1000 cycles. Teeth then were coated with nail polish up to 1mm from the interface, immersed in 50% silver nitrate solution for 24h and tested for nanoleakage using Quanta Environmental SEM and EDAX. Data statistically-analyzed using two-way ANOVA and Tukey's post-hoc tests (P≤0.05). Results: group 2 in which nanoparticles dissolved in water showed the statistically significantly highest percentages of silver penetration (3.21). Meanwhile, there was no statistically significant difference between group 1(1.18) and group 2 (1.3). Whereas, group 4 (0.58) showed the statistically significantly lowest mean percentages of silver penetration. Thermocycled subgroups (1.82) showed statistically significantly higher percentages of silver penetration than non-thermocycled subgroups (1.31). Conclusions: under the test conditions, addition of hydroxyapatite nanoparticles to the adhesive provided better sealing ability. Aging of the restorations as a function of thermocycling, had increased nanoleakage.