Effect of Nb₂O₅ on Mechanical Properties of Novel Resin-Based Sealant

Objectives: To develop an experimental resin-based sealant (RS) incorporated with different concentrations of niobium pentoxide (Nb₂O₅) and evaluate its physical and mechanical properties.
Methods: Five RS compositions were formulated using an organic matrix of BisGMA/TEGDMA (1:1), polymerization initiator (camphorquinone + ethyl-4-dimethylaminobenzoate – EDMAB), polymerization reaction inhibitor system (2, 6-di-tert-butyl-p-cresol – BHT), and Nb₂O₅ at different concentrations: 0 wt.% (control group, GC), 2 wt.% (Nb2%), 5 wt.% (Nb5%) and 10 wt.% (Nb10%). Physical characterization of the Nb₂O₅ and RS was performed using scanning electron microscopy (SEM). Mechanical properties were assessed through flexural strength (FS) (n = 12), flexural modulus (FM) (n = 12), surface roughness (Ra) (n = 12), and microhardness (n = 12) tests. Statistical analysis was performed using one-way ANOVA/Tukey’s test (α = 5%), considering the assumptions of normality and homoscedasticity.
Results: SEM analysis revealed an average size of 28.8 μm for Nb₂O₅ particles, which appeared in irregular shapes with a tendency to agglomerate. GC and Nb2% groups exhibited the highest FS in comparison to the other groups, reaching 84.32 MPa and 76.52 MPa, respectively (p < 0.05), however, no differences were noted between GC and Nb2% (p > 0.05). GC presented the highest FM (2.68 GPa), while the lowest (1.34 GPa) was observed for Nb10% group (p < 0.05). No differences in Ra was found among groups (p>0.05). Nb2%, Nb5%, and Nb10% exhibited higher microhardness than GC (p < 0.05); however, no difference was noted among these Nb-containing groups (p > 0.05).
Conclusions: The incorporation of 2 wt. % Nb₂O₅ does not alter the mechanical characteristics of RS in comparison to those of the GC. However, higher Nb₂O₅ concentrations (i.e., 5 wt. % and 10 wt. %) exhibited lower FS and FM of the RS.