Aging‐Induced Changes in Bulk Properties of Ion‐Releasing Bulk‐Fill Resin Composites

This study evaluates the impact of water aging on the properties of bulk‐fill composites. Three composites were tested: Filtek One Bulk (non‐ion‐releasing control), Beautifil Bulk Restorative (S‐PRG‐based multiple‐ion‐releasing), and Fill‐Up! (fluoride‐releasing glass‐based) as ion‐releasing. Surface morphology, roughness, apparent porosity, relative density, compressive strength (CS), and diametral tensile strength (DTS) were assessed. The data were analyzed using two‐way ANOVA ( α = 0.05). All composites exhibited progressive surface degradation, with ion‐releasing composites showing significantly higher surface roughness after 10,000 cycles (Beautifil Bulk Restorative: 1.25 μm; Fill‐Up!: 1.33 μm) compared to Filtek One Bulk (0.81 μm). The apparent porosity decreased with aging across groups, but relative density declined most sharply in the Fill‐Up! group (10.61%). While CS and DTS initially increased after 5000 cycles, prolonged aging reduced mechanical performance, particularly in Beautifil Bulk Restorative (CS: 30.63 ± 4.17 MPa after 10,000 cycles). Micro‐CT revealed structural voids and filler‐matrix debonding in ion‐releasing composites, correlating with mechanical declines. Ion‐releasing composites exhibit compromised bulk stability under aging, suggesting a potential compromise in structural stability associated with ion‐releasing formulations. Optimization of ion‐releasing formulations is needed to balance remineralization benefits with mechanical stability under aging, though long‐term clinical performance requires further study.