Direct and indirect eluates from bulk fill resin-based-composites

Area of Science:

• Dental Materials Science
• Biocompatibility Testing
• Polymer Chemistry

Background:

• Bulk-fill resin-based composites (BF-RBCs) are increasingly used in dental restorations.
• Understanding the elution of substances from BF-RBCs is crucial for assessing biocompatibility.
• The role of the tooth structure and adhesive system in modulating substance release is not fully understood.

Purpose of the Study:

• To compare direct elution from BF-RBCs with indirect elution from restored teeth.
• To identify elutable (co)monomers, impurities, and potentially toxic substances.
• To evaluate the barrier function of the residual dentin/adhesive layer.

Main Methods:

• Six BF-RBC materials were tested.
• Human third molar teeth with Class-I cavities were restored with BF-RBCs and a three-step adhesive system.
• Control specimens of direct BF-RBCs were prepared.
• Elution was performed in ethanol/water (3:1) at 37°C for 7 days.
• Eluates were analyzed using high-temperature gas chromatography/mass spectrometry.

Main Results:

• Direct BF-RBC eluates contained significantly higher amounts of (co)monomers like bisEMA and TEEGDMA compared to tooth groups.
• The dentin/adhesive layer acted as a diffusion barrier for most substances, except TEGDMA and DEGDMA.
• TEGDMA was found in much higher concentrations in tooth groups, indicating release from the adhesive system.
• Substances of Very High Concern (SVHC), including TINUVIN® 328 and BPA, were primarily found in direct BF-RBC eluates.

Conclusions:

• Biocompatibility assessment requires evaluating the entire system (BF-RBC + adhesive), not just the composite alone.
• Elution tests should analyze not only (co)monomers but also other released ingredients and impurities.
• The adhesive system plays a significant role in the elution profile of dental restorations.