Week 9- Composite Update Flashcards
What are the 3 main components of composite resin materials?
- Matrix (continuous phase, comonomer system)
- Filler (dispersed phases, filler particles)
- Coupling agent (internal interface coupling agent, glues filler into matrix)
What are the other 4 components of CR?
- Initiator/accelerator system
- Stabilizers (storage)
- Bonding system (external interface coupling agent)
- Pigments (coloration and radiolucency)
What are the filler sizers?
- Macrofiller
- Microfiller
- Nanofiller
- Nanomeres
- Nanocluster
What % should fillers make up CR?
Up to 80% volume
What does a higher amount of nanofillers achieve?
- Increases translucency (particles are smaller than wavelength of light)
- Reduces polymerization stress
What is polymerisation (shrinkage) stress and what is the consequence?
When we fill cavity and cure it, the CR shrinks during polymerisation. CR is pulled from cavity walls towards the centre.
Loss in volume creates force between CR and walls and creates stress inside the CR. If bonding system is not good, the shrinkage stress can lead to gap formation inside the interface between CR and tooth, resulting in open margins.
What is required to prevent polymerisation shrinkage?
To prevent this, we have to make sure the CR itself is stress resistant. This means in needs internal elasticity.
What is shrinkage stress a product of?
- Free shrinkage (imposed by bonding to tooth surface)
- Size and nature of monomers
- Acquisition of stiffness
- Rate of reaction
What is the modern external interface coupling?
Bonding agent acts on dentine and enamel at same time
What is the range of viscosity for CR?
- High viscosity hybrid
- Packable composite
- Flowable composite
How can viscosity of CR be adjusted?
- Heat
- Ultrasound
What is Ormorcer?
- Newer CR monomer that has been discontinued
- Has low shrinkage but higher toxicity, failed to meet longevity standards, lower wear resistance and lower marginal adaptation.
What is the main issue with Siloran?
Incompatible with standard dentine adhesives
Why is elasticity of CR important?
Elasticity important for lowering polymerization stress
What does the addition of dendritic copolymers do?
- Enhance copolymerization
- Increased degree of conversion
- Increased polymer elasticity
- Modify rheological behavior (viscosity)
What characteristics of CR reduce polymerization shrinkage and stress?
- Large monomers
- Low amount of small comonomers
- Stress breaking comonomers
- High amount of nanofillers
What are clinical properties of CR based on new monomer technology?
- High mechanical stability
- Good marginal integrity
- High translucency
- Good polishability
- Viscosity adjustable
What are problems with general composites?
- Time consuming (2-3mm increments necessary)
- Post op sensitivity possible (partially cured composite or bad adhesive technique)
What are bulk fill materials?
- New class of materials
- Can use 4-5mm increments
- 2 viscosity classes (low or high viscosity)
What are clinical applications for bulk fill material?
- Bulk fill using low or high viscosity BF material
- Laminate using low viscosity BF material and high viscosity convention CR
- Laminate using low viscosity BF material and high viscosity BF material
- Laminate using high viscosity BF material and high viscosity conventional CR/
What are problems with bulk fill materials?
- Low viscosity BF materials have all problems of general flowables
- High translucency
- Limited sculptability
- Depth of cure 4-5mm (but for some materials, high curing light intensity is required)
What are developments of future monomers in CR?
- Self adhesive systems (place material and cure- no dentine adhesive required)
- Radiopaque monomers
- Fluoride-containing monomer
- Antibacterial monomer
What are developments of future fillers?
- Plaque and bacteria inhibiting composites
- Remineralisation
- New filler types
- Use of short fibres to reinforce CR
- Nanodiamond particles
- Flake shaped glass fillers
- Prepolymerised spherical fillers
What are general developments of future CR?
- Laminate systems
- Photo initiators (increase depth of cure)
- Polymerisation methods (polymerisation modulator to decrease polymerisation stress)
What is laminate system?
Smart combination of dentine and enamel replacement
- Dentine: flexible material as stress breaker
- Enamel: strong wear resistance material
