Objectives : The aim of the study was to evaluate the influence of different levels of nanoparticles, dispersed in an commercial, unfilled adhesive, on the adhesive strength to dentin. The compounding of nanoparticles in either the primer or in the adhesive was observed as well as the distribution of the particles in the hybrid and adhesive layer.
Materials and methods : Coronal dentin of freshly extracted, non-carious human third molars was prepared for bonding with the nanoparticle modified adhesive (Scotchbond MP = SMP, 3M ESPE, Germany). Different amounts of experimental zirconia particles ( d 50 = 70 nm; 0% vs. 5% vs. 20% (w/v)) were dispersed in either the primer or adhesive solution oft SMP. Following storage in distilled water at 37 °C @ 24 h, the bonded specimens were sectioned into μTBS slabs ( n = 40; 0.49 mm 2 ), using a low-speed diamond saw (Isomet; Buehler, Germany). μTBS was measured in a universal testing machine (1 mm/min; Zwick, Germany). Cross sections of adhesive layers were qualitatively examined under TEM. Data were analyzed using ANOVA and mod. LSD test ( p < 0.05).
Results: Table 1 μTBS [MPA] of the tested adhesives.
| Adhesive | Strength/MPa |
|---|---|
| SMP | 25.2 ± 10.9 (a) |
| SMP + 5% zirconia/primer | 33.6 ± 15.6 (b) |
| SMP + 20% zirconia/primer | 41.1 ± 13.1 (b, c) |
| SMP + 5% zirconia/adhesive | 34.7 ± 13.6 (b) |
| SMP + 20% zirconia/adhesive | 32.3 ± 15.3 (b) |
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