A new acrylic-based fluoride-releasing cement as a potential orthodontic bonding agent.

OBJECTIVE: To develop a fluoride-releasing, acrylic-based 'easy on, easy off' bracket cement as a potential orthodontic bonding agent. MATERIAL AND METHODS: Three experimental cements were prepared in powder/liquid forms by mixing different ratios of methylmethacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) to form the liquid (L) and sodium fluoride (NaF) and polymethylmethacrylate (PMMA) to form the powder (P). The resultant materials were tested for setting characteristics, fluoride release, hardness, strength, shear bond strength (SBS) and adhesive remnant index in comparison with resin composite and glass ionomer, which were used as control materials. The data were analyzed using ANOVA and the Kruskal-Wallis and Mann-Whitney tests. RESULTS: The experimental groups had satisfactory setting characteristics. Fluoride release of the group containing P (10% NaF, 90% PMMA) and L (60% MMA and 40% HEMA) was similar to that of glass ionomer. When experimental materials were stored in water for 7 days, their hardness was reduced and stabilized at a value lower than those for composite and PMMA. Strength was only slightly affected by water storage. The SBSs of the experimental groups were considered clinically acceptable at both 30 min and 1 month. The group containing P (10% NaF, 90% PMMA) and L (90% MMA and 10% HEMA) had a higher mean SBS than the other two experimental groups. At 1 month, there were significantly less adhesive remnants observed on the surface of enamel after debonding for the experimental groups compared with the composite. CONCLUSION: The new cement could potentially be useful as an orthodontic bonding agent.

Fluoride release for restorative materials and its effect on biofilm formation in natural saliva.

This study investigated the influence of natural saliva of varying pH on surface biofilm formation of restorative materials and how this influenced fluoride release. Columnar specimens of glass ionomer cement (GIC), resin modified glass ionomer cement (RMGIC), compomer, giomer and composite, were prepared, matured for 24 h at 37 degrees C and 100% humidity, lapped and then placed in natural stimulated saliva with a pH of 3.8 or 7.1. Fluoride release was determined daily using an ion-selective electrode. The surfaces of selected specimens were observed using Confocal Laser Scanning Microscopy in conjunction with a fluorescent dye. The surface biofilm formation and bacterial growth was most dominant under neutral conditions and on the surfaces of GICs compared with other materials. GICs released significantly higher amounts of fluoride than other materials. The results suggest that the increased fluoride release of GICs did not reduce the amount of bacterial growth and biofilm formation on the surfaces of these materials when stored in natural saliva.

Fluoride release and neutralizing effect by resin-based materials.

This study evaluated the fluoride-releasing and neutralizing abilities of resin-based materials containing fluoride in water and aqueous lactic acid. Two composites, containing a low-solubility fluoride component (Heliomolar) and a fluoroalumino-silicate glass (UniFil S), and two giomers, containing surface reaction type prereacted glass-ionomer filler (Beautifil) and full reaction type glass-ionomer filler (Reactmer paste), were used. Resin-modified glass-ionomer cement (Fuji II LC) was used as a control. The fluoride release and pH value in storage medium, after immersion in each material, was measured for 10 weeks. For UniFil S and Beautifil, the amount of fluoride released in acid solution markedly increased compared to storage in water (p<0.05). Although all materials, except Heliomolar, neutralized the storage media, the neutralizing ability of these resin-based materials in acid solution sharply decreased with aging of the specimens, except for Fuji II LC. These results suggest that the nature of fluoride incorporated into resin-based materials affect the fluoride-releasing and neutralizing ability of materials in water and aqueous lactic acid.

Fluoride release from aged resin composites containing fluoridated glass filler.

OBJECTIVES: The aim of this study was to evaluate the fluoride release from aged resin composites containing different types of fluoridated glass filler into both deionized distilled water and lactic acid solution. METHODS: Three resin composites, UniFil S (containing fluoro-alumino-silicate glass filler), Reactmer (containing pre-reacted glass-ionomer filler) and Beautifil (containing both types of fillers) were used. A conventional glass-ionomer cement, Ketac-Fil, was used as a control. Five disk specimens of each material were prepared and aged in water for 10 weeks. After aging, specimens were immersed in deionized distilled water for a further 6 days and then in aqueous lactic acid (pH 4.0) for 2 days. This process was repeated twice more and the specimens were subsequently immersed in water for a further 12 days. Fluoride release was measured every 2 days throughout the post-aging period. RESULTS: The amount of fluoride release for aged UniFil S and Beautifil markedly increased in acid solution compared with water storage. The difference was not so great for aged Reactmer and Ketac-Fil. UniFil S and Beautifil gave significantly greater fluoride release in water following immersion in acid solution (p<0.05, two-way ANOVA and Scheffe's test), but Reactmer and Ketac-Fil showed no such increase in fluoride release after acid immersion. SIGNIFICANCE: These results suggested that the nature of the fluoridated glass filler within a resin composite and the way in which the material interacts with an acidic environment affected the amount of fluoride released.