3D Printing Resin Composite: Influence of Microfiller Loading Level

Objectives: The aim of this study was to evaluate the influence of microfiller loading level of barium glass in a methacrylate-based 3D printing resin composite.
Methods: Experimental resins were formulated with UDMA 70%wt, Bis-EMA 20%wt, and TEGDMA 10%wt. Photoinitiators TPO and DFI (2%wt) were used. Barium glass, with a particle size of 0.7 µm, was incorporated at loading levels of 0%, 40%, and 50%wt. Varseo Smile Crown Plus (BEGO) was utilized as a commercial control. Specimens were 3D printed using a Photon Mono 4K LCD (Anycubic) printer. Subsequently, they were washed with 96% ethanol for 5 minutes and cured using a UV curing unit (FormCure, Formlabs) for 2 sessions of 20 minutes each at 60°C. Viscosity (n=3) was measured using a rheometer with cone-and-plate geometry, flexural strength (n=5) was determined according ISO 4049, degree of conversion (n=5) was assessed by FTIR, polymerization kinetics (n=3) were analyzed by PhotoDSC with 100mw/cm2, softening in solvent (n=5) by knoop hardness, radiopacity (n=5) according ISO 4049, and cytotoxicity on fibroblasts was assessed by MTT and SRB. Data were statistically analyzed using one-way ANOVA (α=0.05).
Results: Viscosity of formulated resins ranged from 1786,0±8.1 cP for G_Varseo to 6936,0±44,0 cP for G_50%. No significant difference in flexural strength was showed between G_40% (90.5±5,4 MPa), G_50% (102.0±11,7 MPa) and G_Varseo (105.2±11.7 MPa), p>0.05. Addition of 40% and 50% of BG showed no influence in degree of conversion compared to G_Varseo (p>0.05). All groups decreased hardness after immersion in ethanol (p<0.05). G_50% showed radiopacity of 2.8±0.3 mmAl, significantly higher than other groups (p<0,05). Cytotoxicity by MTT and SRB showed between G_40%, G_50% and G_Varseo (p>0.05), with all results above 80% of cell viability.
Conclusions: Addition of 50% barium glass showed promising results at experimental methacrylate-based 3D printing resin composite.