Long-term fluoride exchanges at restoration surfaces and effects on surface mechanical properties

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Caries Prevention Research

Background:

• Fluoride-releasing dental composites aim to provide cariostatic benefits beyond mechanical restoration.
• Long-term stability of fluoride release and mechanical properties is crucial for clinical efficacy.

Purpose of the Study:

• To evaluate the 18-month fluoride release, fluoride recharge capacity, and mechanical stability of three fluoride-containing resin composites.
• To compare these properties against a glass ionomer control.

Main Methods:

• Specimens of Beautifil II, Gradia Direct X, Tetric EvoCeram, and Fuji IX Extra were subjected to bimonthly fluoride release/recharge analysis.
• Nanoindentation assessed hardness and elastic modulus at baseline and up to 18 months.
• Fluoride rerelease and mechanical properties were measured after an 18-month aging period followed by sodium fluoride gel recharge.

Main Results:

• Beautifil II and Gradia Direct X maintained significant fluoride release and recharge capabilities throughout the 18-month aging period.
• Fluoride rerelease from Beautifil II after recharge was comparable to the long-term release of Fuji IX Extra.
• No significant changes in hardness or elastic modulus were observed for the tested composites after 18 months of aging and testing.

Conclusions:

• Beautifil II and Gradia Direct X exhibit excellent long-term fluoride release, recharge, and mechanical stability, making them suitable for load-bearing restorations in high caries risk individuals.
• The sustained fluoride release and recharge potential of these composites may reduce caries incidence on adjacent unrestored tooth surfaces.