Composite

mechanical – strength, rigidity, hardness bonding to tooth / compatible with bonding systems thermal properties aesthetics handling / viscosity smooth surface finish/ polishable low setting shrinkage​ radiopaque anticariogenic biocompatible

microfine silica​ quartz​ borosilicate glass​ lithium aluminium silicate​ barium aluminium silicate

bisphenol-A and glycidyl methacrylate​

• difunctional molecule ​ (C=C bonds – facilitate crosslinking) undergoes free radical addition polymerisation

Camphorquinone

Camphorquinone – ​ -activated by blue light ​ -produces radical molecules -these initiate free radical addition polymerisation of BIS-GMA -leading to changes in resin properties (ie increased molecular weight, so increased viscosity, and strength) causes degree of conversion of resin: 35-80%

added to adjust viscosity & reactivity

good bond between filler particle and resin is essential normally water will adhere to glass filler particles, preventing resin from bonding to the glass surface a coupling agent is used to preferentially bond to glass and also bond to resin

Surrounds the glass fillers allowing better bonding between them and the resin

condensable - “amalgam feeling” - greater porosity ​ syringeable - good adaptation, less porosities, easy to apply​ flowable - lower filler content, more shrinkage, difficult to apply, place for them -with fibre ribbons

improved mechanical properties​ -strength, rigidity, hardness, abrasion resistance etc​ lower thermal expansion (still not perfect)​ lower polymerisation shrinkage (still a problem)​ less heat of polymerisation (BUT not negligible)​ improved aesthetics​ some radiopaque

self curing (two pastes)​ UV activation (obsolete, one paste)​ Light curing ​ -blue light 440nm​(one paste) direct curing (in mouth)​ indirect curing / post curing​(in laboratory)

Free radicals from the reaction break the resin c=c bonds polymerisation (formation of chain)

benzoyl peroxide + aromatic tertiary amine

extended working time​ -on-demand set, triggered when light activated​ less finishing​ immediate finishing​ less waste​ higher filler levels (not mixing two pastes)​ less porosity (not mixing two pastes)

Most of blue light absorbed close to surface which sets readily and becomes hard

Column of composite light cured, soft comp scraped off, measured distance of hard comp is then divided by 2 giving the depth of cure

DoC is defined as depth at which material HARDNESS is about 80% that of the cured surface​ the depth to which the composite resin polymerises sufficiently

typically 2mm

2mm as greater than this wikk result in under-polymerised bases -soggy bottom and poor bonding to tooth

Tetric evoceram

Lucerin initiator as well as camphorquinone​ ​ Has different optical absorption spectrum ​ hence UV and blue light ​ needed to polymerise (cure) material fully ​

light / material mismatch - overexpose premature polymerisation from dental lights - avoid exposure optimistic “depth of cure” values​ -product, shade, light exposure & intensity​ -use small increments - 2 mm max recommended setting times too short​ -product, light used, light/ material distance, ​ -contamination or damage to light guide, ​ -timer accuracy, ​ -variations in light output (eg over repeated use, between different units)​ use > 30 s​ polymerisation shrinkage ​ -affects bond to tooth, ​ -potential for cuspal fracture, microleakage ​ - use small increments - light from different angles

Exothermic reaction so adjacent enamel and dentine can conduct heat up to 16 degree rise Divergent light beam - unless optical rod is ALWAYS close to the composite resin surface ​ SOME blue light MAY illuminate patient’s soft tissues and may cause thermal trauma ​ two clinical incidents in 2017​