Glass ionomer cement

• conventional GI • resin modified GI

• dressing (temp material) • fissure sealant • endodontic access cavity temporary filling • luting (e.g. for crowns) • orthodontic cement • restoration of deciduous teeth • restoration of permanent teeth • base or lining under permanent restoration

• acid - polyacrylic acid and tartaric acid • base - silica, alumina, calcium fluoride, aluminium fluoride, aluminium phosphate, sodium fluoride

increase the radiopacitiy of the material so it is more visible in radiographs

the more silica, the more translucent the material and the better the aesthetics

• anhydrous materials - acid is freeze dried and added to the powder, the liquid added is distilled water • encapsulated materials - consistent power to liquid ratio and more consistent properties

<20um

• quicker setting reaction • more opaque cement

• the higher the molecular weight, the better the mechanical properties of the set material • the higher the molecular weight, the more viscous and diffucult to mix the GIC is

M = metal A = polyacid

• dissolution • gelation • hardening

• acid is in solution • H+ ions from acid attach to the glass surface • Ca, Al, Na and F ions are released • silica gel is left around the unreacted glass

• bivalent calcium ion crosslinking with the polyacid by chelation with carboxyl groups cause the initial set of the material (2 crosslinks) • takes several minutes to initial set • formation of calcium polyacrylate • the material will appear hard in the mouth but is not fully set

• trivalent aluminium ions ensure good crosslinking and increases the strength (3 crosslinks) • aluminium polyacrylate forms after a long time - does not start for 30 mins and can take over a week to complete • greatly improves the mechanical properties of the set material

• aluminium ions diffuse out of material and becomes less hard - mechanical properties are reduced • excessive drying means water will be lost • saliva contamination can cause absorption of water • leads to a weak material which will be rough, break up and have poor aesthetics

• varnishes e.g. copal ether, acetate • resins e.g. dentine/enamel bonding agents, unfilled Bis-GMA resins • greases or gels e.g. vaseline (can be removed quickly by lips or tongue)

Tartaric acid improves ease of use with a long working time and a short setting time

• can bond to enamel and dentine without the need of an intermediate material • bond strength is not high compared to composite on etched enamel • good sealing ability with little leakage around margins

chelation reaction between carboxyl groups in the cement and Ca on the tooth surface

• a clean surface • a conditioned surface (little/no tissue removes to get a clean smooth surface)

• poor tensile strength - brittle • lower compressive strength than composite • poorer wear resistance than composite - susceptible to abrasion • lower hardness than composite • higher solubility than composite - long term erosion by acids • moisture susceptible when first placed • poor aesthetics • susceptible to acid attacks and drying out over itme • possible problems bonding to composite

• good thermal properties - expansion similar to dentine • no contraction on setting unlike composite • less susceptible to staining and colour change after setting than composite • good chemical bond to enamel and dentine • low microleakage • releases fluoride • lower modulus

• releases fluoride without damaging their structure • has a high initial fluoride release but diminishes very quickly over the first week • GICs can take up fluoride when the F concentration around them is higher (toothpaste) • they can release fluoride again when the ambient concentration falls

RMGIC is light cured, has improved physical properties and better aesthetics - composites properties added to GIC