The Effect of Light-Curing Devices and Modes on the Physical Properties of Three Universal Single-Shade Resin Composites

Objectives The objective of this in vitro study was to assess the microhardness, surface roughness, and hardness ratios of three universal single-shade resin composites using a variety of light-curing units (LCUs) and modes. Materials and Methods A total of 150 resin composite specimens were prepared (In each subgroup, n=10), each measuring 5 mm in diameter and with a depth of 2 mm, from three universal single-shade resin composites: Charisma Diamond One/DO, Omnichroma/OC, and Vittra APS. Two modes of a Valo cordless LCU and two modes of a Woodpecker LCU were selected to cure the resins, and an Elipar S10 LCU was used as a control. Vickers hardness measurements were taken from the samples using the HMV-G, while surface roughness was measured using the Surfest SJ301 device. Data were analyzed using Shapiro–Wilk, two-way robust ANOVA, Bonferroni tests, and Spearman's rho correlation. Results The highest average microhardness was achieved on the top surfaces of the FGM resin composite using the Valo in high-power mode, with significant differences from other combinations. A statistically significant interaction was observed between resin composite types and LCUs on curing depth (p=0.001), with the deepest curing found in the Tokuyama resin composite using the Valo in high-power mode. The highest surface roughness occurred with the FGM composite using the Valo in standard mode. Additionally, a partial correlation was identified between microhardness and surface roughness across the study groups. Conclusions In this study's limitations, three single-shade resin composites showed favorable outcomes, with Kulzer having the highest microhardness, Tokuyama achieving the greatest curing depths, and FGM exhibiting the highest surface roughness. Valo's high-power mode, used for 4 seconds, yielded the highest hardness ratio but did not attain the highest microhardness value; this was achieved by the Elipar device. Nonetheless, Valo's high-power mode is beneficial for reducing chair time.