Composite 1

• new dental caries • abrasion / erosion • failed restoration/secondary caries • trauma

• Filler particles • Resin • Camphorquinone • Low weight dimethacrylates • Silane coupling agent

types of glass – microfine silica – quartz – borosilicate glass – lithium aluminium silicate – barium aluminium silicate

Monomers used:- – BIS-GMA - reaction product of bisphenol-A and glycidyl methacrylate – urethane dimethacrylates

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

– 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)

added to adjust viscosity & reactivity

– 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

• Curing method – light cured • self cured • Filler type: – microfilled • submicron hybrid • heavily filled • Handling characteristics – condensable – syringeable – flowable

• filler particles • curing (activation) • particle /resin bonding

• 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) • Light curing (blue light 440nm, one paste)

self curing = benzoyl peroxide + aromatic tertiary amine light curing = camphorquinone + blue light = free radicals are formed (polymerisation)

halogen LED

• 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 is absorbed close to the surface. Composite resin nearest the surface sets the most readily and becomes hard.

• Surface hardness profile is accepted as more realistic • Instrumentation used to create indentations on surface, that are quantified • And then sub-surface measurements related to this • DoC is defined as depth at which material HARDNESS is about 80% that of the cured surface

Depth of cure – the depth to which the composite resin polymerises sufficiently it’s HARDNESS is about 80% (to 90%) of the cured surface (D = 0mm) typically 2mm indicates increment thickness to use when building a restoration using increment > 2mm results in UNDER-POLYMERISED base “soggy bottom” poor bonding to tooth….early failure !

2mm

Has lucerin initiator as well as camphorquinone UV and blue light needed to polymerise (cure) material fully produce a deeper DOC resulting in less time wasted

4-6mm

• light / material mismatch - overexpose • premature polymerisation from dental lights - avoid exposure • optimistic “depth of cure” values (small increments) • recommended setting times too short • polymerisation shrinkage

thermal trauma from heat generation (exothermic reaction) ocular damage from intense light sources,