In Vitro Analysis of Marginal Sealing Using Light Curing Techniques on Aged and Unaged Composite Resins

To evaluate the marginal sealing of resin composite restorations subjected to various lightcuring protocols, both with and without artificial aging through thermocycling. A comparative, longitudinal in vitro experimental study was performed with 120 bovine teeth distributed across 8 groups. The teeth were treated with different light intensities (650-1200 mW/cm², 800 mW/cm², 1200 mW/cm², 2500-2800 mW/cm²) along with different curing times (15", 20", 10", 3"), as described in the ISO 11405-2015 standard. Thermocycling comprised of 10,000 cycles to replicate one year of intraoral conditions, and microleakage was measured with dye penetration and the Khera and Chan scale (0-3). The majority of samples (41.7%) displayed dye penetration in the middle third of the interface (grade 2). Significant differences were detected among samples with and without thermocycling in the specific groups (p=0.027 and p=0.013), confirming a possible effect of artificial aging. For the highest light intensities (2500-2800 mW/cm²), no significant differences were present (p=0.527), indicating a possible lower effect of thermocycling at these intensities. The results demonstrate that marginal sealing varies by curing protocols and aging processes. Thermocycling affected microleakage with moderate light intensity, while higher intensities and shorter curing times had a reduced effect. These results point to the need for optimizing the curing protocols to provide better long-term durability for the restoration. Further work should examine other variables that may alter marginal sealing.