Composite Restorative Material part I Amalgam Composite Gold

Restoration Classified into: Direct Restoration Indirect Restoration

Direct Restorative Materials Direct gold restoration Amalgam restoration Direct aesthetic restoration Silicate restorative material Acrylic restorative material Composite restorative material

Ideal requirements of aesthetic restorative material Shade match, shade stable Biocompatible Not dissolve is oral fluids Have adequate mechanical properties Have strength & modulus of elasticity similar to tooth Good abrasive resistance Coefficient of thermal expansion similar to tooth Minimal dimensional changes with setting High polishability Radioopaque Adhere to tooth structure

Silicate restorative material Introduced since 1903 Advantages: Translucency of glass powder Anticariogenic property Disadvantages: Poor biological response Dissolution No longer used any more

Acrylic restorative material Early clinical failure related to dimensional instability => Gap between restoration and tooth => Stain, sensitivity, & recurrent caries No longer used any more

Composite filling material Introduced in 1960s Composite: is combination of 2 or more chemically different materials with interface separating the components Dental composite: refer to resin restorative material consisting of 2 phases: inorganic fillers dispersed in continuous resin matrix system that will induce polymerization,

Basic components of composite Resin matrix Inorganic fillers Coupling agent Initiator accelerator system Inhibitor Optical modifiers

Organic matrix phase Principal high molecular weight monomer (oligomer) Diluent (lower molecular weight monomer)

Principal high molecular weight monomer (oligomer) Majority is Bisphenol A-glycidyl methacrylate (BIS-GMA) also called bowen’s resin Or Urethane dimethacrylate (UDMA) Advantages of oligomers over methyl methacrylate Lower polymerization shrinkage Lower volatility More rapid hardening Result in stiffer and stronger resin

UDMA advantages over BIS-GMA Lower viscosity Lower water sorption Greater toughness Greater susceptibility to visible light curing

Oligomers contain carbon double bond at each end => free radical addition polymerization => rigid cross-linked polymer Oligomers are viscous => incorporation of inorganic fillers is difficult => addition of diluent

Diluent Low molecular weight monomers added to: Diluents are either: reduce viscosity => proper blending with inorganic component Facilitate clinical manipulation Diluents are either: Diethylene glycol dimethacrylate Triethylene glycol dimethacrylate

Inorganic Fillers Consist of several materials: quartz, borosilicate glass, lithium aluminum silicate, barium aluminum silicate, strontium or zinc glass, or colloidal silica Heavy elements => radioopacity

Role of inorganic fillers Improve mechanical properties eg. Compressive strength, modulus of elasticity, hardness Higher filler => better mechanical properties Reduce coefficient of thermal expansion Glass is able to reflect color of surrounding tooth structure Reduce polymerization shrinkage Less heat generation Barium or strontium => radioopacity

Filler particle size and shape Macrofilled Microfilled Hybrid Nanofilled Nanohybrid

Macrofilled Large particle size 20-30 µm Adv. Disadv. Irregular filler shape => better retention to resin matrix Disadv. Large filler => difficulty in finishing and polishing Discoloration and staining

Midifilled 0.5 – 3 µm Same as macrofilled composite

Microfilled 0.04 - 0.2 µm Adv. Disadv. Give shiny surface Disadv. Difficult to add => 25% fillers Solved by adding filler to oligomer of low viscosity => cured => gound 10 – 20 µm => added to more viscous oligomer Fillers are called organic fillers or prepolymerized fillers Result in 32-50 % fillers

Hybrid composite Contain mixture of macro & micro fillers Combine the adv. Of both types Higher mechanical properties (macro) Good surface finish (micro) Contain up to 70 % of fillers

Nanofilled Nanomers 2-75 nm individual particles or Nanoclusters 5-20 nm particles clustered together into 0.6-1.4 µm Adv. Highly transluscent Higher mechanical properties: up to78.5 % fillers Lower polymerization shrinkage High polishability

Nanohybrid composite Contains large particles 0.4-5 µm with added nanomers