Glass Ionomer

polyacrylic acid and tartaric acid

silica dioxide, almunia dioxide, alumium fluoride, calcium fluoride

anhydrous - mix liquid and powder, can change ratio to have different properties, liquid is distilled water, freeze dried acid is added to powder encapsulated - same mix all the time, stable, easier to use

smaller - sets faster, better for cementing crowns etc bigger - slower set

more acid - thicker, more viscous, increased mechanical properties

dissolution, gelation, hardening

acid and base mix, hydrogen ions attack the silica, causes it to release calcium, sodium, aluminium and fluoride ions. The unreacted silica becomes covered in a silica gel as silica mixes with water

calcium ions are bivalent, can bond to two molecules. Allows for cross linking within the polyacrylic acid, results in calcium polyacrylate forming. Cross linking increases mechanical properties, this will appear hard in the mouth although hardening is not finished

aluminium ion is trivalent, can bond to 3 molecules. Can bond to polyacrylic acid to form aluminium acrylate, however, this can take hours, days or a week for it to be complete. this further increases the strength

as it can take days to completely harden, needs to be conditioned to prevent any moisture entering the restoration

water from saliva being absorbed, aluminium ions diffuse out of material, excess drying result in a weak restoration, will be rough, break up and have poor aesthetics

it reduces the setting time to make it easier to handle

calcium ions on enamel surface can bond to the polyacryclic acid to aid cross linking

good bond to the tooth - good marginal seal although the bond strength is much lower compared to composite low thermal conduction, good thermal expansion - expands at same rate as enamel and dentine, prevent microleakage, no contraction on setting, fluoride release

fluoride release peaks initially and then reduces over time so little is released. however, thought it can act as a reservoir, when fluoride levels are high, it will absorb it and then when they dip it can release

poor mechanical strength - 100MPa compared to 300MPa of composite, poor aesthetics

HEMA - resin polyacrylic acid contains methacrylate monomers photo initiators barium glass - radiopacity potassium persulphate - REDOX iniator

same steps as conventional but has the resin to set. Mixing of acid and base as before, then light cure causes polymerisation of resin and the methacrylate groups in polyacrylic acid. After, REDOX reaction for further polymerisation. Acid base reaction continues

the REDOX reaction should ensure all resin polymerisations even in dark, however, mechanical properties are reduced by 25% and unpolymerised HEMA is toxic to pulp

same steps as conventional, mixing of acid and base. REDOX reaction begins also at this stage, some polymerisation of resin. then light cure, more polymerisation. After, REDOX and acid base reactions continue

initially better bond strength and properties. Resin increases mechanical strength. better aesthetics,

light curing slows down acid base reaction, polymerisation contraction shrinkage, unpolymerised HEMA is toxic to pulp

contains benzyl iodides and bromides which are cytotoxic to bacteria, however, can also be toxic to pulp

as a lining under a restoration, luting cement for crowns, orthodontic cement, temporary restoration over access cavity for endodontics