Optimizing Dental Resin-Based Composite Polymerization with Distance and Exposure Variables: Preliminary Study

Resin-based composites (RBCs) are widely used in restorative dentistry, and their clinical performance depends on the degree of conversion (DC). Light-curing units are used to initiate polymerization, but factors such as the distance between the light source and the composite surface as well as different exposure modes can affect DC. This study aimed to evaluate the effect of curing distance on the DC of resin-based composites under different polymerization modes. Specimens of a standardized resin-based composite were prepared and cured using a light-emitting diode (LED) curing unit at varying distances (0 mm, 2 mm and 4 mm). Three exposure modes were applied: standard, soft-start, and pulse. The DC of the cured composites was determined using Raman scattering spectra measurements. The DC differed significantly depending on the evaluated factors and the measurement location within the samples (top vs. bottom). For measurements taken at the top of the samples, a highly significant effect of material type on the degree of conversion was observed (p-value < 0.001). Distance also showed a statistically significant influence (p-value = 0.049), whereas exposure mode did not significantly affect DC at the top surface (p-value = 0.391). Both curing distance and exposure mode significantly influence the polymerization efficiency of resin-based composites. Minimizing the distance between the light source and composite surface improves the DC, and selecting an appropriate exposure mode can partially compensate for increased distance. Clinicians should consider these factors to optimize the mechanical properties and longevity of composite restorations.