What are the properties of glass ionomers?
In contrast, glass-ionomer cements (GICs) have interesting properties such as biocompatibility, bioactivity, fluoride release, excellent coefficient of linear thermal expansion/contraction and modulus of elasticity, as well as being the only restorative material capable of chemically bonding to the tooth structure 6 .
What are ionomers used for?
Commercial applications for ionomers include golf ball covers, semipermeable membranes, sealing tape and thermoplastic elastomers. Common examples of ionomers include polystyrene sulfonate, Nafion and Hycar. Ionomer: A polymer composed of ionomer molecules. or ionic groups, or both.
What is composition of GIC?
All GICs contain a basic glass and an acidic polymer liquid, which set by an acid-base reaction. The polymer is an ionomer, containing a small proportion – some 5 to 10% – of substituted ionic groups. These allow it to be acid decomposable and clinically set readily.
How does GIC bond?
In the case of a conventional (self-cure) GIC, the bond between the GIC and resin composite filling material is micromechanical in nature and mediated by a resin-based enamel/dentin bonding system. The original etch-and-rinse systems used aggressive acid etching to form a micromechanical bond to tooth structure.
What are the advantages of glass ionomer cement?
Glass ionomer cements exhibit a number of advantages over other restorative materials. By bonding a restorative material to tooth structure, the cavity is theoretically sealed, protecting the pulp, eliminating secondary caries and preventing leakage at the margins.
How does GIC release fluoride?
Fluoride release from GICs restorations following a continuous uptake process increases the fluoride concentration in saliva and in adjacent hard dental tissues. Thus, continuous small amounts of fluoride surrounding the teeth decreases demineralization of the tooth tissues.
What is ionomer resin made of?
Ionomer resins are primarily composed of ethylene copolymerized with small amounts of vinyl and acid (such as methacrylic acid) groups. The copolymer has both covalent and ionic bonds. Ionomers crosslink to form a plastic that is resistant to abrasion, breaking, and chemicals.
What is the mixing time of GIC?
Mixing time as a factor Mechanical mixing is likely to produce a mixture of GIC with good consistency and results in better survival rate of the restorations. For the materials used in the study, the manufacturer’s recommended mixing times were 10, 30 and 20 s, respectively, for KMA, KME and Fuji IX.
How many types of glass ionomers are there in concrete?
Three main types of glass-ionomer cement are commonly used. They have different compositions and properties. These types are: conventional glass-ionomer cement.
How does GIC bond to dentin?
Both types of glass ionomer cements are adhesive to enamel and dentin via ionic bonding of the glass ionomer to the calcium and phosphate ions of the tooth. It usually takes 24 hours for the final adhesive values to be attained.
What is GIC tooth filling?
Glass ionomer is essentially a flexible paste, that is used to form a tight seal between the internal tooth (exposed, due to a cavity) and the surrounding environment. It acts as a sealant, allowing the tooth to remain protected.
What are the physical properties of ionomers?
Ionomers have unique physical properties including electrical conductivity and viscosity—increase in ionomer solution viscosity with increasing temperatures (see conducting polymer). Ionomers also have unique morphological properties as the non-polar polymer backbone is energetically incompatible with the polar ionic groups.
Why are ionic-group polymers not considered ionomers?
These two classes of ionic-group-containing polymers have vastly different morphological and physical properties and are therefore not considered ionomers. Ionomers have unique physical properties including electrical conductivity and viscosity —increase in ionomer solution viscosity with increasing temperatures (see conducting polymer ).
What happens to ionomers when heated?
When heated, the ionic bonds and clusters dissolve and when cooled, they reform. This gives ionomers a unique structure and behavior. At low temperatures they behave like crosslinked polymers (elastomers) and at elevated temperatures like ordinary thermoplastics.
What is glass ionomer adhesive?
Glass ionomer adhesive is considered a two-step etch-and-rinse adhesive, its chemical composition is based on the glass ionomer cement. It is the diluted version of the RMGI cement, Fuji II LC. Glass ionomer is the only material that has the self-adhering property.