The Effect of Curing Conditions on Fluoride-Releasing Dental Materials

Abstract

Bioactive restorative materials have been developed to combine the fluoride release of glass ionomers with the strength of resin composites. However, their performance under clinically relevant curing conditions and environmental challenges remains unclear. This thesis evaluated the properties of bioactive materials and compared them with established materials under clinically relevant in vitro conditions. Materials and methods: Five materials were examined: two bioactive resin composites (Activa BioACTIVE Restorative and Cention Forte in light-cured (LC) and self-cured (SC) modes), two resin-modified glass ionomers (Photac Fil and Vitremer), and a conventional composite (Filtek Z250). Specimens were tested for degree of conversion (DC), water sorption, solubility, fluoride release, and Vickers hardness. Curing distance (0-8 mm) was evaluated. Storage was performed in distilled water and artificial saliva at neutral (AS7) and acidic (AS4) pH. Results: Under recommended curing instructions, Z250 showed the highest hardness and lowest sorption. RMGICs exhibited high DC but lower hardness. Activa showed lower hardness than both RMGICs and Z250 and released minimal fluoride. In contrast, Cention released fluoride comparable to RMGICs, but had lower DC. Between the two curing modes, Cention LC showed higher DC and hardness, whereas Cention SC released more fluoride and had the lowest hardness. Increasing curing distance to ≥4 mm reduced DC and hardness in Activa and Cention, while Z250 and RMGICs were less affected. Artificial saliva influenced material behaviour: sorption was higher at pH7, whereas pH4 produced reduced or negative sorption in Cention and RMGICs. Fluoride release increased at AS4 for all materials except Activa. Hardness ranked pH7 > DW > pH4, with Photac and Cention SC most affected by acid, while Z250 remained stable. Conclusion: Overall, none of the bioactive composites matched the fluoride release of RMGICs and the mechanical durability of conventional composites, highlighting the challenge of achieving sustained fluoride release alongside long-term durability.