Commercially Available Fluoride-Releasing Restorative Materials: A Review and a Proposal for Classification

Abstract

Resin composite and glass ionomer cement (GIC) are the most commonly used dental materials to perform direct restorations. Both have specific characteristics that explain their popularity and their limits. More than 20 years ago, the first attempt (followed by others) to combine the advantages of these two families was performed with compomers, but it was not very successful. Recently, new formulations (also called 'smart materials') with claimed ion release properties have been proposed under different family names, but there are few studies on them and explanations of their chemistries. This comprehensive review aims to gather the compositions; the setting reactions; the mechanical, self-adhesive, and potential bulk-fill properties; and the ion release abilities of the large existing families of fluoride-releasing restorative materials and the new restorative materials to precisely describe their characteristics, their eventual bioactivities, and classify them for an improved understanding of these materials. Based on this work, the whole GIC family, including resin-modified and highly viscous formulations, was found to be bioactive. Cention N (Ivoclar Vivadent, AG, Schaan, Lietschentein) is the first commercially available bioactive resin composite.

Keywords: Activa BioActive Restorative; Cention N; GIC; HV-GIC; RM-GIC; Surefil One; bioactive materials; compomer; giomer; nanoionomer.

Figure 1

Legends for the illustrations presented in the following figures.

Figure 2

Conventional GIC in its storage medium. The powder contains FAS fillers that are not silanated, whereas the liquid contains water and ionized polyacrylic acids.

Figure 3

Ion release processes from a conventional GIC once it is in a moist environment (i.e., an oral environment). When the powder and liquid are mixed, the acid–base reaction is initiated, the setting of the material begins, and the FAS fillers are partially attacked. A silicic gel is partially formed on the FAS filler surface. The released calcium and aluminum ions are able to form ionic bonds with the ionized carboxylic groups. Fluoride ions are also released. In water, calcium, aluminum, and fluoride ions (and eventually other ions) are able to be exchanged with the oral environment.

Figure 4

HV-GIC in its storage medium. The powder contains nonsilanated FAS fillers in which very small FAS fillers are added to speed up the reaction and increase the powder/liquid ratio. The liquid contains water and ionized polyacrylic acids.

Figure 5

Ion release from an HV-GIC once it is in a moist environment (i.e., an oral environment). The mechanism of the reaction and ion exchange with the oral environment are the same as that previously described for conventional GIC.

Figure 6

An RM-GIC in its storage medium. The powder, in contrast with GICs and HV-GICs, contains silanated FAS fillers; the liquid contains the same components as those in the GIC liquid but with HEMA monomers added to the formulation.

Figure 7

Ion release from an RM-GIC once it is in a moist environment (i.e., an oral environment). When the powder and liquid are mixed, the acid–base reaction is initiated, the setting of the material begins, and the FAS fillers are partially attacked: a silicic gel is partially formed on the FAS filler surface. The released calcium and aluminum ions are able to form ionic bonds with ionized carboxylic groups. Fluoride ions are also released. A second reaction of resin polymerization is activated when the material is light-cured: monomers can copolymerize with other monomers or silanated FAS fillers. At the end of the reaction, two different interpenetrated networks are produced without covalent or ionic links between both. In water, calcium, aluminum, and fluoride ions (and eventually other ions) are able to be exchanged with the oral environment.

Figure 8

Vitremer in its storage medium. The powder contains silanated FAS fillers, and some chemopolymerization components are added. The liquid contains water, an ionized modified polyacrylic acid with photopolymerizable groups, camphorquinone as a photoinitiator, and some chemopolymerization components.

Figure 9

Ketac Nano in its storage medium. The first paste contains silane-treated reactive FAS fillers and unreactive fillers, as well as HEMA monomers. The second paste contains water, an ionized modified polyacrylic acid with photopolymerizable groups, camphorquinone as a photoinitiator, a blend of monomers including HEMA, and silane-treated unreactive fillers.

Figure 10

Ion release from Vitremer (left) or Ketac Nano (right) once they are in contact with a moist environment (i.e., oral environment). When the powder and liquid (or pastes for Ketac Nano) are mixed, the acid–base reaction is initiated, the setting of the material begins. Once the FAS fillers are partially attacked, a silicic gel partially forms on the FAS filler surface. The released calcium and aluminum ions are able to form ionic bonds with ionized carboxylic groups. Fluoride ions are also released. A second reaction involving resin polymerization occurs during mixing for Vitremer (chemopolymerization) or during light curing for Ketac Nano. Monomers can copolymerize with silanated FAS fillers and other monomers for both materials and silanated unreactive fillers for Ketac Nano. At the end of the reaction, two interconnected networks are obtained with covalent links between both due to the modified polyacrylic acid (Vitrebond copolymer). In water, calcium, aluminum, and fluoride ions (and eventually other ions) are able to be exchanged with the oral environment.

Figure 11

A compomer in its storage medium. This material contains, schematically, silane-treated reactive FAS fillers and unreactive fillers, a blend of monomers including dehydrated acidic monomers and camphorquinone, but does not contain any water.

Figure 12

Ion release from a compomer once it is in contact with the oral environment. When the material is light cured, a resin polymerization reaction is initiated, and monomers can copolymerize with other monomers, silanated FAS fillers, and unreactive fillers. The acidic groups remain dehydrated, and no acid–base reaction occurs in the setting reaction of the material. When placed in a moist environment (i.e., oral environment), water sorption occurs, and dehydrated acidic monomers located in the periphery of the material can release protons to attack silanated FAS fillers. This mechanism leads to the release of calcium, aluminum, and fluoride ions. These ions do not participate in the setting mechanism of the material.

Figure 13

A giomer in its storage medium. This material contains, schematically, a silane-treated partially pre-reacted FAS filler (S-PRG), an unreactive filler, and a blend of monomers and camphorquinone. It does not contain any water.

Figure 14

Diagram of ion release from a giomer once it is in contact with the oral environment. When the material is light cured, a resin polymerization reaction is initiated, and monomers can copolymerize with other monomers, silanated S-PRG fillers, and unreactive fillers. No acid–base reaction occurs in the setting reaction of the material. When placed in a moist environment (i.e., oral environment), water sorption occurs, and S-PRG fillers are able to release calcium, aluminum, and fluoride ions. These ions do not participate in the setting mechanism of the material.

Figure 15

Diagram of Activa BioActive Restorative in its storage medium. The powder contains silanated FAS fillers, some chemopolymerization components, and silanated unreactive fillers. The liquid contains water, polyacrylic acid, a blend of monomers including phosphate dimethacrylate monomers, camphorquinone as a photoinitiator, and some chemopolymerization components.

Figure 16

Diagram of ion release from Activa BioActive Restorative once it is in contact with a moist environment (i.e., oral environment). When the powder and liquid are mixed, the acid–base reaction is initiated, the setting of the material begins, and the FAS fillers are partially attacked. A silicic gel partially forms on the FAS filler surface. The released calcium and aluminum ions are able to form ionic bonds with ionized carboxylic groups. Fluoride ions are also released. A second reaction of resin polymerization occurs during mixing: monomers can copolymerize with silanated FAS fillers, silanated unreactive fillers, and other monomers. At the end of the reaction, we obtain two different interpenetrating networks with theoretical ionic links between both with trivalent ions. In water, calcium, aluminum, and fluoride ions (and eventually other ions) are able to be exchanged with the oral environment.

Figure 17

Diagram of Cention N in its storage medium. The powder contains, schematically, silane-treated FAS filler, silanated ‘alkasite’ filler, unreactive filler, and some chemopolymerization components. The liquid contains a blend of monomers, Ivocerin as a photoinitiator, and some chemopolymerization components. It does not contain any water.

Figure 18

Diagram of ion release from Cention N once it is in contact with the oral environment. When the material is mixed, a resin polymerization reaction is initiated due to the chemical initiator, and monomers can copolymerize with other monomers, silanated FAS filler, silanated alkasite fillers, and unreactive fillers. No acid–base reaction occurs in the setting reaction of the material. When placed in a moist environment (i.e., oral environment), water sorption occurs in FAS fillers, and alkasite fillers are able to release calcium, aluminum, and fluoride ions (and eventually other ions). These ions do not participate in the setting mechanism of the material.

Figure 19

Surefil One in its storage medium. For RM-GICs, the powder contains silanated FAS fillers, some chemopolymerization components, and silanated unreactive fillers. The liquid contains water, an ionized modified polyacrylic acid with photopolymerizable groups, a blend of monomers, camphorquinone as a photoinitiator, and some chemopolymerization components.

Figure 20

Ion release from Surefil One once in contact with a moist environment (i.e., oral environment). When the powder and liquid are mixed, the acid–base reaction is initiated, the setting of the material begins, and the FAS fillers are partially attacked. A silicic gel is partially formed on the FAS filler surface. The released calcium and aluminum ions are able to form ionic bonds with ionized carboxylic groups. Fluoride ions are also released. A second reaction of resin polymerization occurs during mixing, where monomers can copolymerize with silanated FAS fillers, silanated unreactive fillers, and other monomers. At the end of the reaction, two interconnected networks are obtained with covalent links between both due to the modified polyacrylic acid (MOPOS). In water, calcium, aluminum, and fluoride ions (and eventually other ions) are able to be exchanged with the oral environment.

Figure 21

Classification of the fluoride-releasing materials according to: the importance of the acid/base reaction or resin polymerization in their setting, their bioactivity, their bulk-fill properties, and their bioactivity.