Fluoride Release, Recharge and Mechanical Property Stability of Various Fluoride-containing Resin Composites

Abstract

Fluoride containing resin composites and especially those containing pre reacted glass ionomer fillers could be employed to great benefit in treating high caries risk patients in situations where glass ionomers may be unsuitable; particularly in high load bearing or aesthetically critical locations. SUMMARYAim: To determine the fluoride release and recharge of three fluoride-containing resin composites when aged in deionized water (pH 6.5) and lactic acid (pH 4.0) and to assess mechanical properties of these composites following aging.Methods: Three fluoride-containing resin composites were analyzed in this study; a new giomer material named Beautifil II, Gradia Direct X, and Tetric EvoCeram. A glass ionomer cement, Fuji IX Extra, was also analyzed for comparison. Specimens were fabricated for two test groups: group 1 included 10 disc specimens initially aged 43 days in deionized water (five specimens) and lactic acid (five specimens). The fluoride release from these specimens was measured using a fluoridespecific electrode on nine specific test days during the aging period. Following 49 days of aging, each specimen was recharged in 5000 ppm neutral sodium fluoride solution for 5 minutes. Specimen recharge was then repeated on a weekly basis for 3 weeks. The subsequent fluoride rerelease was measured at 1, 3, and 7 days after each recharge episode. Group 2 included six disc specimens aged for 3 months in deionized water (three specimens) and lactic acid (three specimens). The hardness and elastic modulus of each specimen was measured using nano-indentation at intervals of 24 hours, 1 month, and 3 months after fabrication. Two-way factorial analysis of variance (ANOVA) and post-hoc (Tukey) testing was used to assess the influence of storage media (two levels) and composite type (three levels) on the fluoride release, fluoride rerelease, hardness, and elastic modulus of the assessed materials. The level of significance was set at p¼0.05.Results: All three composites demonstrated fluoride release and recharge when aged in both deionized water and lactic acid. The cumulative fluoride released from Beautifil II into both media was substantially greater than the fluoride released from Gradia Direct X and

Influence of Different Mechanisms of Fluoride Release from Adhesive Systems

“…Although the S-PRG-based adhesive released less fluoride than the PEM-F-based adhesive, the former showed a high level of fluoride uptake by dentin and enamel. These findings were recently corroborated by another study (5).…”

“…In addition, the acidified water within the hydrogel surrounding the inner glass of S-PRG particles facilitates fluoride release by the continuing dissolution of the fluoride-containing glass core. Giomers are different from compomers because the glass ionomer hydrogel within the compomers forms only after water uptake by the resin matrix after polymerization (5,8).…”

“…The low amount of fluoride release from FLB could be related to extrinsic factors such as the storage medium, the experimental design and analytical methods used to evaluate the fluoride release behavior (5,9,19,20). The storage medium influences the fluoride release values, which vary if the storage solution is replaced daily or used cumulatively (19).…”

“…Yet, dental materials release more fluoride in deionized water than in artificial saliva due to the cations present in the artificial saliva (20). In addition, another study showed a greater fluoride release in lactic acid than in water (5). This behavior indicates that these materials may show a higher capacity of providing fluoride to the tooth structure at the moments when the Fluoride release from adhesive systems adjacent enamel is most susceptible to demineralization.…”

“…However, a few problems are still of major concern, including resin composite polymerization shrinkage, which is responsible for the formation of gaps at the adhesive interface (3,4). These gaps allow the infiltration of fluids and microorganisms that could cause secondary caries and result in restoration replacement (2,5).…”