Ion release from, and fluoride recharge of a composite with a fluoride-containing bioactive glass

Abstract

Objectives Materials that are capable of releasing ions such as calcium and fluoride, that are necessary for remineralization of dentin and enamel, have been the topic of intensive research for many years. The source of calcium has most often been some form of calcium phosphate, and that for fluoride has been one of several metal fluoride or hexafluorophosphate salts. Fluoride-containing bioactive glass (BAG) prepared by the sol-gel method acts as a single source of both calcium and fluoride ions in aqueous solutions. The objective of this investigation was to determine if BAG, when added to a composite formulation, can be used as a single source for calcium and fluoride ion release over an extended time period, and to determine if the BAG-containing composite can be recharged upon exposure to a solution of 5,000 ppm fluoride. Methods BAG 61 (61% Si; 31% Ca; 4% P; 3% F; 1% B) and BAG 81 (81% Si; 11% Ca; 4% P; 3% F; 1% B) were synthesized by the sol gel method. The composite used was composed of 50/50 Bis-GMA/TEGDMA, 0.8% EDMAB, 0.4% CQ, and 0.05% BHT, combined with a mixture of BAG (15%) and strontium glass (85%) to a total filler load of 72% by weight. Disks were prepared, allowed to age for 24 h, abraded, then placed into DI water. Calcium and fluoride release was measured by atomic absorption spectroscopy and fluoride ion selective electrode methods, respectively, after 2, 22, and 222 h. The composite samples were then soaked for 5 min in an aqueous 5,000 ppm fluoride solution, after which calcium and fluoride release was again measured at 2, 22, and 222 h time points. Results Prior to fluoride recharge, release of fluoride ions was similar for the BAG 61 and BAG 81 composites after 2 h, and also similar after 22 h. At the four subsequent time points, one prior to, and three following fluoride recharge, the BAG 81 composite released significantly more fluoride ions (p<0.05). Both composites were recharged by exposure to 5,000 ppm fluoride, although the BAG 81 composite was recharged more than the BAG 61 composite. The BAG 61 composite released substantially more calcium ions prior to fluoride recharge during each of the 2 and 22 h time periods. Thereafter, the release of calcium at the four subsequent time points was not significantly different (p>0.05) for the two composites. Significance These results show that, when added to a composite formulation, fluoride-containing bioactive glass made by the sol-gel route can function as a single source for both calcium and fluoride ions, and that the composite can be readily recharged with fluoride.

Cytotoxicity of resin composites containing bioactive glass fillers

“…they were equivalent to the control culture without composite). In other work, we have verified that these composite formulations do release calcium and fluoride ions, but apparently they did not contribute significantly to the cell response [38]. Further evidence that the BAG itself was not cytotoxic was apparent when comparing the three different BAG-containing formulations, which showed no statistical difference in cytotoxicity despite the composites having 5, 10 or 15% BAG.…”

Novel rechargeable calcium phosphate dental nanocomposite

“…The recharging properties of F-releasing materials were investigated using topical fluoride agents or fluoride-containing toothpastes [44-48]. Glass ionomer cements (GIs), RMGIs, and compomers were shown to release, absorb, and re-release fluoride ions.…”

Influence of biofilm formation on the optical properties of novel bioactive glass-containing composites

“…The BAG-F filler particle used in the present study had a larger surface area than the BAG filler [6]. This increased surface area for a soluble particle enhances the dissolution rate of ions from the glass [42].…”

“…A recent study reported that BAG containing composites showed mechanical properties comparable to commercial composites [2]. Also, adding a filler particle based on a fluoride-containing BAG (BAG-F) enabled the composite to release both calcium and fluoride ions in solution, and to be rechargeable with fluoride upon exposure to external fluoride solutions [6]. While these properties provide optimism about the potential use of BAG additives in composites, the potential dissolution of the glass filler may cause concern about the integrity of the resin composite surface, and its overall esthetic appearance during aging.…”