Curing behaviour of high-viscosity bulk-fill composites

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• High-viscosity bulk-fill resin-based composites (RBCs) offer clinical advantages for posterior restorations.
• Understanding the influence of curing parameters on their mechanical properties is essential for predictable clinical outcomes.
• Previous research has focused on lower viscosity materials or different curing protocols.

Purpose of the Study:

• To evaluate the effect of various curing conditions on the micromechanical properties of high-viscosity bulk-fill RBCs.
• To determine optimal curing parameters for achieving adequate depth of cure and mechanical integrity at clinically relevant depths.
• To compare the responses of different high-viscosity bulk-fill RBCs to varying curing protocols.

Main Methods:

• Three high-viscosity bulk-fill RBCs were tested under 16 different curing conditions.
• Micromechanical properties (Vickers hardness and indentation modulus) were measured at 200μm intervals within simulated 6mm deep fillings.
• Curing parameters included exposure time (5-40s), mode (standard, high power, plasma), and exposure distance (0-7mm). Energy density ranged from 2.63 to 47.03J/cm(2).

Main Results:

• Material type significantly influenced all measured properties (hardness, modulus, depth of cure).
• Energy density had the strongest effect on mechanical properties across all materials.
• Exposure distance significantly impacted depth of cure but had less effect on hardness and modulus.

Conclusions:

• High-viscosity bulk-fill RBCs exhibit heterogeneous responses to curing variations.
• Specific energy density thresholds were identified for 4mm and 5mm bulk placements, varying by material.
• A 20s exposure time at moderate irradiance is recommended for 4mm bulk placement to ensure adequate mechanical properties.