Thermodynamic Control of Polymerization Kinetics and Mechanical Properties in Resin-Based Composites

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Physical Chemistry

Background:

• Resin-based composites (RBCs) are widely used in dentistry.
• Understanding RBC polymerization kinetics is crucial for clinical success.
• Current protocols often rely on irradiance, but thermal effects are less understood.

Purpose of the Study:

• To develop a quantitative framework for RBC polymerization kinetics.
• To integrate thermodynamic, chemical, and mechanical parameters.
• To establish predictive correlations between these parameters.

Main Methods:

• Investigated three RBC formulations under varying thermal, irradiance, and spectral conditions.
• Utilized differential scanning calorimetry (DSC) to measure polymerization enthalpy (ΔH) and kinetics.
• Correlated thermodynamic metrics with degree of conversion (DC), Vickers hardness (VHN), and depth of cure (DoC) via non-linear regression.

Main Results:

• Temperature significantly influenced polymerization dynamics (Arrhenius kinetics); 50°C increased ΔH (up to 67%), DC, and VHN.
• A radiant exposure threshold of 8 J/cm² was identified for thermodynamic saturation.
• Non-linear regression models showed strong correlations (R² > 0.90) between ΔH and mechanical properties.

Conclusions:

• Pre-heating, irradiance, and formulation impact RBC thermodynamic and mechanical properties.
• Non-linear regression confirmed a robust relationship between ΔH, DC, and VHN.
• Thermal energy is more effective than high irradiance for driving polymerization kinetics, guiding optimized clinical protocols.