Mechanical Stability of Self-Adhesive/Ion-Releasing Resin Composites

The purpose of this study was to assess the effects of water storage on the surface microhardness (VHN) and fracture toughness (K1C) of two self-adhesive restorative materials compared to traditional resin composite and resin-modified glass ionomer cement (RMGIC) restorative materials. Methods: Two self-adhesive materials (Activa and Vertise Flow), a nonflowable composite (Filtek Z250), and an RMGIC (Fuji II) were evaluated. Hardness measurements (n = 12) were recorded at three time intervals: (i) one-hour post-irradiation; (ii) after one day of storage in water at 37 °C; and (iii) after 90 days of storage in water at 37 °C. Fracture toughness (K1C) measurements (n = 12) were conducted after one day of storage in water at 37 °C and 90 days of storage in water at 37 °C. ANOVA and Tukey post hoc tests were used for statistical analysis. Results: Baseline VHN data were 38.2–58.3, decreasing significantly to 28.8–55.6 following 90 days of water storage. The Filtek Z250 had the highest VHN before and after storage, while the Activa had the lowest. KIC values varied between 0.98–1.32 MPa·m0.5. The highest value was for the Filtek Z250 while the Fuji II showed the lowest value (after both 1 and 90 days of storage in water). However, KIC values decreased significantly after storage, except for the Fuji II. Conclusion: Self-adhesive/ion-releasing resin composites were negatively affected by water storage. Material reinforcements are possible future areas to explore.