Glass Ionomer

Restorative - filling materials (riva, vitremer) Core build up - prior to restoration with crown (vitremer crown core) Lining - underneath permanent fillings (vitrebond, ionoseal) Luting - cementing indirect restorations (fuji luting, vitremer luting cement, aquachem)

Polyacrylic acid (ionic monomers) - usually copolymers of acrylic and itaconic acid or acrylic and maleic acid Tartaric acid - added to control the setting times

— Silica, SiO2 (Silicone dioxide) 30% - 40% — Alumina, Al2O3 (Aluminium dioxide) 15% - 30% — Calcium Fluoride, CaF2 15% - 35%

can increase the radiopacity but these play no part in the reaction chemistry.

The ratio of alumina/silica alters the translucency. More silica more translucent.

anhydrous materials (no water) — The acid is freeze dried and added to the powder — The liquid is distilled water — This makes for easier handling of the material, particularly mixing encapsulated materials — Consistent powder/liquid ratio — Easier to use — Should be more consistent properties of the mixed material

The smaller the particle size the quicker the setting reaction and the more opaque the set cement. <20 micrometres

— Dissolution — Gelation — Hardening

Acid (H+ ions) attacks the glass powder, releasing metal ions (Ca, Al, Na & F). Leaves silica gel around unreacted glass

initial set due to calcium ion crosslinking with polyacrylic acid forming calcium polyacrylate several minutes

Continued crosslinking with aluminum ions for increased strength over time forming aluminium polyacrylate increased strength process does not start until 30 minutes and takes a week

— It is important that GIC is protected from moisture and dessication following gelation. — This is when it is ‘set hard’ in the mouth but before maturation has begun

— Aluminium ions diffuse out of the material — Excessive drying means water will be lost — Saliva contamination causes absorption of water — All lead to a weak material which will be rough, break up and have poorer aesthetics

varnish (acetate) resins (DBA, unfilled Bis-GMA)

removed by action of lips and tongue

Tartaric acid, this greatly improved their ease of use — Working time is largely unchanged but setting time is shortened

— Can bond to enamel and dentine without the need for use of an intermediate material — Bond strength not high compared with composite, about 5MPa — Good sealing ability with little leakage around margins

— Chelation between carboxyl groups in the cement and Ca on the tooth surface. — Re-precipitation of complex mixture of calcium phosphate (from apatite) and calcium salts from the polyacid onto and into the tooth surface — Hydrogen bonding or metallic ion bridging to collagen

— Clean surface — Conditioned surface — Conditioned, not etched. — Little or no tissue is removed. — Best conditioner appears to be polyacrylic acid —Purpose is to produce clean smooth surface

higher translucency = better aesthetics

Lower compressive strength than composite. Less than half. 80 – 110MPA Poorer wear resistance than composite, subject to abrasion Lower hardness than composite Higher solubility than composite (dissolution of unprotected material during gelation phase, and long term erosion by acids) Good thermal properties expansion similar to dentine No contraction on setting Once set less susceptible to staining and colour change than composites Fluoride release (recharge) Brittle Low aesthetics

Initial fluoride release but this diminishes very quickly, over the first week. then recharges from environment

Developed to overcome Glass Ionomer brittleness Silver was added to the glass (equal volumes) to increase toughness and wear resistance. No evidence that this was the case, only ended up making a silver coloured GIC. Looks like dull amalgam

Powder: Fluoro-alumino-silicate glass, barium glass, polyacrylic acid, initiators Liquid: HEMA (resin), polyacrylic acid with methacrylate groups, water, initiators