Flexural properties of rapidly prototyped denture base materials; the effect of nanoparticles addition and post-curing duration in vitro

Shaimaa M Fouda ¹ Mohammed M. Gad ^1* Mai El Zayat ¹ Soban Khan ¹ Sultan Akhtar ¹ Ahmed Othman ² Constantin Von See ²

• ¹ Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia
• ² Department of Health Sciences, Medicine and Research, Faculty of Health and Medicine, Danube University Krems, Krems an der Donau, Lower Austria, Austria

The flexural strength and elastic modulus of rapidly prototyped denture base materials are affected by numerous factors including reinforcement with nanoparticles (NPs) and post curing duration (PCD), though the effect of these two factors together was overlooked. The present study tested the effect of nano-diamonds (NDs) or Silicone dioxide nano-particles (SNPs) with various post-curing duration (PCD) on the flexural strength and elastic modulus of rapidly prototyped denture base materials. Methods: To measure the flexural strength and elastic modulus, bar-shape specimens (64x10x3.3mm) were designed and rapidly prototyped using ASIGA and NextDent denture base resins. Each resin (N=150) was divided into 5 groups (n=30) according to NPs type and concentrations; pure group as a control without additive, 0.25% NDs, 0.5% NDs, 0.25% SNPs and 0.5% SNPs. Specimens from each group were further divided into 3 groups (n=10) and post cured for 15, 60, or 90 minutes, followed by thermocycling for 5000 cycles. After measuring the flexural strength and elastic modulus using three point bending test, a scanning electron microscope was employed to analyze the fractured surface. The bonds between the NPs and the resin were tested by Fourier Transformed Infrared. ANOVA and post hoc tests were used for data analysis (α=0.05). Results: The flexural strength increased with prolonged PCD and the highest values for all tested groups was reported at 90-min (P<0.001).The flexural strength of both materials increased significantly with NDs and SNPs addition in comparison to pure groups (P<0.05). K-factors ANOVA analysis for elastic modulus showed that each factor (NPs type, PCD, material type) showed significant effect on elastic modulus (P <0.001). Conclusion: The flexural strength and elastic modulus of rapidly prototyped denture base resin were increased with NDs or SNPs addition and with increasing the PCD. The selection of the factors including nanoparticle type and concentration, the post-curing duration and the material type solely or in combination could affect the flexural strength and elastic modulus of prototyped denture base materials.