Fluoride release and recharge in giomer, compomer and resin composite

The purpose of this study was to analyze the ions released from a surface pre-reacted glass ionomer (S-PRG) filler in distilled water or lactic acid solution. S-PRG filler was mixed with either solution at 1000:1, 100:1, 10:1, and 1:1 ratios by weight. By means of inductively coupled plasma atomic emission spectroscopy and a fluoride electrode, elements released from S-PRG filler were identified to be Al, B, Na, Si, Sr, and F. To investigate the effect of solution pH on ion release, the pH values of the solutions before mixing and after 24 hours' mixing with S-PRG were measured. After 24 hours' mixing, the pH values of solutions at all ratios became more neutral or weakly alkaline regardless of their initial pH levels before mixing. In conclusion, results showed that S-PRG filler released several types of ions, and that ion release was influenced by the mixing ratio of the solution rather than the initial pH of the solution.

Detection of ions released from S-PRG fillers and their modulation effect.

This paper reviews our recent studies on fluoride-releasing adhesives and the related studies in this field based on information from original research papers, reviews, and patent literatures. A revolutionary PRG (pre-reacted glass ionomer) filler technology--where fillers were prepared by the acid-base reaction of a fluoroaluminosilicate glass with polyalkenoic acid in water, was newly developed, and a new category as "Giomer" was introduced into the market. On fluoride release capability, SIMS examination revealed in vitro fluoride ion uptake by dentin substrate from the PRG fillers in dental adhesive. On bonding durability, it was found that the improved durability of resin-dentin bonds might be achieved not only via the strengthened dentin due to fluoride ion uptake from the PRG-Ca fillers, but also due to retention of relatively insoluble 4-AETCa formed around remnant apatite crystallites within the hybrid layer in 4-AET-containing self-etching adhesives. On ultramorphological study of the resin-dentin interface, TEM images of the PRG-Ca fillers revealed that the dehydrated hydrogel was barely distinguishable from normal glass fillers, if not for the concurrent presence of remnant, incompletely reacted glass cores. In conclusion, it was expected that uptake of fluoride ions with cariostatic effect from PRG-Ca fillers would endow dentin substrates with the benefit of secondary caries prevention, together with an effective and durable adhesion to dentin.

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A review of chemical-approach and ultramorphological studies on the development of fluoride-releasing dental adhesives comprising new pre-reacted glass ionomer (PRG) fillers.

Optimizing filler content in an adhesive system containing pre-reacted glass-ionomer fillers.

Determination of fluoride ions released from resin-based dental materials using ion-selective electrode and ion chromatograph

This study investigated the release and recharge of fluoride by restorative materials. Resinmodified glass ionomers (RGIs), polyacid-modified composite resins (PMCRs) and resin composite containing fluoride were used for comparison of fluoride release. Non-fluoride-releasing resin composite was used as a control. The amounts of fluoride release from RGIs and PMCRs remarkably increased in the citrate-phosphate acid buffer compared with distilled water. The amounts of fluoride recharged in RGIs increased with the concentration of NaF solution, but those of PMCRs exposed to all concentrations of NaF solutions were less than 1.5ppm. Neither resin composite containing fluoride and non-fluoride-releasing resin composite gave any evidence of recharge. RGIs and PMCRs affected by acid buffer solution could not recharge much fluoride even if they were immersed in the 1000ppmF NaF solution. The results suggested that the matrix of RGIs and PMCRs functioned as a reservoir of fluoride, but the functions were lost by acid attack.

Mimiko Okamoto

Papers

Release and recharge of fluoride by restorative materials.