Toughening and polymerization stress control in composites using thiourethane-treated fillers

Area of Science:

• Materials Science
• Biomaterials Engineering
• Polymer Chemistry

Background:

• Dental composites often suffer from polymerization stress and limited fracture toughness.
• Surface functionalization of filler particles is a key strategy to improve composite properties.
• The precise mechanism by which thiourethane oligomers enhance dental composites remains unclear.

Purpose of the Study:

• To systematically investigate the impact of thiourethane-silane (TU-Sil) functionalization on dental resin composites.
• To characterize the physicochemical properties of experimental composites with varying filler sizes and concentrations.
• To establish structure-property relationships between filler surface modification and composite performance.

Main Methods:

• Barium glass fillers were functionalized with thiourethane-silane (TU-Sil) or methacrylate-silane (MA-Sil) and compared to untreated fillers (No-Sil).
• Filler particles were incorporated into a BisGMA-UDMA-TEGDMA resin matrix at different weight percentages.
• Properties evaluated included polymerization kinetics (near-IR), polymerization stress (cantilever system), fracture toughness (single edge-notched beams), and filler surface morphology (SEM, confocal microscopy).

Main Results:

• TU-Sil functionalization reduced polymerization stress by 41-54% and increased fracture toughness by an average of 35% compared to MA-Sil.
• Filler surface coverage by TU-Sil was non-uniform and dependent on filler size, forming thicker layers (up to 206 nm for 1 µm particles) than traditional silanes.
• Composite viscosity remained unaffected by the thiourethane oligomer grafting.

Conclusions:

• Tailoring the organic-inorganic interface with thiourethane oligomers is an effective strategy to enhance dental composite performance.
• This approach significantly reduces polymerization stress and improves fracture toughness.
• The findings provide a basis for designing advanced dental restorative materials with improved mechanical properties.