W11. Composites Flashcards
What are 9 indications of composites in dentistry?
- Class I., II., III., IV., V., VI restorations (fillings, inlay/onlay/overlay)
- Resin based cement for indirect restoration
- Aesthetic enhancement procedures (veneers, diastema closures)
- Fissure sealents
- Core buildups
- Periodontal splinting
- Fixation of orthodontic bracket
- Treatment of patients with metal allergic
- Temporary restorations
What is Composite?
Three dimensional combination of at least two chemically different materials with a distinct interface in between them
What are the ingredients of composite?
The ingredients have different chemical and physical properties, and the combination of the materials will result in a more resistant, rigid and solid material..
- Organic phase - matrix
- Inorganic dispersed phase –fillers
- Coupling phase - silane
Identify these parts of composite
- Organic phase - matrix
- Inorganic dispersed phase –fillers
- Coupling phase - silane
What is the Constitution of the matrix of composites?
Constitution of the matrix
=> Identify
BIS-GMA bisphenol-A-glycidyl methacrylate
Constitution of the matrix
=> Identify
UDMA uretan-dimetacrilate
Constitution of the matrix
=> Identify
TEGDMA triethilen-glikol-dimetacrilate
What is the role of Photopolymerization?
Using light (420-480nm) to initiate and propagate a polymerization reaction to form a crosslinked polymer structure.
What are the features of silane?
- Coupling agent improve the adherence of resin matrix to filler particles ’ surfaces
- Bipolar molecule: chemically connects the hydrophobe matrix and the hydrophil inorganic disperse phase with covalent bond .
- covers the inorganic phase, joins its hydroxyl groups
- the other end is able to bind to the double bonds of the monomer of the matrix
Inorganic fillers
1. What are the 2 main functions of Inorganic fillers?
- Reinforce the soft matrix with crystals
- Determine the physical properties of composites
Inorganic fillers
2. The role of inorganic fillers is to reinforce the soft matrix with crystals
=> What are these crystals?
- Quartz
- Glass fibers (barium glass, stroncium glass)
- Silicate, aluminum, zirconium
Inorganic fillers
3. The role of Inorganic fillers is to determine the physical properties of composites
=> What are these properties?
- hardness,
- durability,
- wear resistance,
- aesthetics, polishability,
- radioopacity (barium strontium, zirconium)
Give the Classification of composites based on the size of the fillers
Give Classification of composites based on the distribution of the fillers
- homogene
- inhomogene/heterogene (contain pre-cured composite particle)
- hybrid (composites with mixed/different particle sizes)
Give Classification of composites based on weight and volume percent
- unfilled resin- bond materials
- Fissure sealent
- Flow composite (low filler content)
- Condensable/packable composite, flow composite with high filler content
Classification of composites by Lutz
1. Give the classification of composites by Lutz
- Conventional composite
- hybrid composite
- Homogene microfilled composite
- inhomogene microfilled composite
Classification of composites by Lutz
2. Identify
- Macrofiller
- Microfiller
- Microfiller-complex
Classification of composites by Lutz
3. Identify
- Silane-coupling agent
- Organic matrix
Classification of composites by Lutz
4. Identify
- Conventional composite
- Hybrid composite
- Homogene microfilled composite
- Inhomogene microfilled composite
What are the 4 main properties of composites?
- We can use for class I-VI. restorations
- Polymerization shrinkage during monomer polymer transformation: resulting local stresses that reduce bonding forces
- Increasing filler content- their physical, chemical and mechanical properties improve
- The size of the fillers determines the aesthetics and polishability of the filling material
One of the properties of composite is to increase filler content which leads to improvement in their physical, chemical and mechanical properties
=> What are these properties?
- More resistant to masticatory forces
- Less polymerization shrinkage
- Less thermal expansion- similar to enamel
- Less water absorption
- Easier to use due to its high viscosity
The size of the fillers determines the aesthetics and polishability of the filling material
=> Explain this further
- Macrofillers
- worse polishability
- rough surface
- plaque retention - Nanofillers
- good polishability
- smooth surface
Describe adhesive technique
- Preparation – minimal invasive preparation, beveling of enamel margin
- Conditioning - pre-treatment of cavity walls, demineralization, more surface for bonding
- Use of adhesives / bond materials - implementation of micromechanical retention
Describe Minimal invasive preparation
- only the caries laesion is removed
- Beveled enamel margins :45o, , width:0,25-0,5 mm
- our goal is to open the enamel prisms and increase the surface for microretention
Class I. : vestibular/oral surface
Class II.: vestibular/oral walls if the approximal box is wide
Class V.: where there is enamel
Class VI.: in the enamel
What do we need to be cautious when it comes to beveling in minimal invasive preparation?
Do not bevel the enamel margins where there is masticatory force, because the thin part of the compsite filling can crack/fracture easily!
What is adhesion?
The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking forces or both
Explain the process of adhesion
- The process of replacing the inorganic dental structure with a synthetic adhesive / bond.
- 2 phases:
1. demineralisation: calcium phosphate is dissolved from the tooth structure, microporosity is created both on the enamel and the dentin
2. hybridisation: penetration and polymerisation of adhesive/bond
Explain the step Conditioning in Composite Filling
Describe dentin
- Dentin contains a substantial proportion of water and organic material
- Less hydroxy-apatit
- Inhomogeneous structure
Describe dentin tubules
- Fluid-filled- hydrated tissue
- Movement of fluid by pulpal pressure form the pulp to the DEJ
- Number of tubules
- Diameter of tubules
Describe smear layer
- Formed during preparation of dentin
- 0,5-5 um organic and anorganic components (dentin chips and microorganisms)
- Plugs in the tubuli- 2-5um deep
What are the 2 techniques that can affect the smear layer?
- Etch and rinse technique- removes the smear layer
- Self etch technique- modifies the smear layer
Demineralization after etching
1. Describe enamel rods after 30 minutes etching
3 patterns of etched enamel:
- The nucleus of the enamel prisms are dissolved
- The periphery of the enamel prisms are
dissolved
- Mixed
Demineralization after etching
2. Describe Dentin collagen matrix after 15’’ etching
- Hydroxy apatit is dissolved
- Smear layer is removed
- Intertubular and peritubular collagen
are exposed by the acid - Dentinal tubules are opened in a
funnel configuration
Explain washing, drying step in Composite filling
- Enamel- not sensitive for drying
- Dentin- SENSITIVE for drying !
- Collagen fibers can collapse
- We use WET bonding with aceton/ethanol based primer- water- chasing effect
What are the features of primer-HEMA?
- Detergent
- Bifunctional molecules:
- hydrophilic group bonds to the dentin
- hydrophobic group bonds to the adhesive
What are the 3 functions of primer-HEMA?
- opens the collagen fibers that have condensed after etching
- Envelops the external surface of collagen fibrils
- Re-establishes surface-free energy
Explain the step Bonding in Composite filling
- Bond is applied to the walls of the cavity with an applicator- Microbrush
- we gently blow it with air
- to spread the material - better penetration
- Make thin layer of bond
- Evaporates the solvent of the bonding agent (acetone, ethanol) - Remove the excess with an exhaustor
- Polymerization-20sec
describe enamel adhesion
The bond material penetrates and polymerizes in place of the dissolved hydroxyapatite crystals due to demineralization
- The periphery of the enamel prisms are dissolved by acid- formation of MACROTAG with the penetration and polymerization of resin
- The nucleus of the enamel prisms are dissolved by acid- formation of MICROTAG with the penetration and polymerization of resin
These are the basis of micromechanical bonding
Due to their frequency, microtags are more important.
Dentin adhesion
1. Describe Dentin adhesion
- Hybridization: Resin infiltration of the dentinal tubules and intertubular dentin
- Resin tag: Primer and bonding resin penetrate and polymerize in the open dentinal tubules, forming resin tags
- Hybrid layer (1982. Nakabayasi) Primer and bonding resins are applied to etched dentin they penetrate the intertubuar dentin (in the collagen matrix), forming hybrid layer
Dentin adhesion
2. What is resin tag?
Primer and bonding resin penetrate and polymerize in the open dentinal tubules, forming resin tags
Give the Classifications of adhesives
What is C-factor?
Configuration factor: The ratio of bonded surfaces to unbonded or free surfaces in a tooth preparation
C-factor
-> Explain this figure
- the polymerization shrinkage generates stress between the bonded walls and the filling material
- more bonded surface- higher stress- higher risk of bond disruption
- the lower the C-factor, the lower the polymerization shrinkage
Application of composite fillings
-> Identify 1, 2, 3, 4
How do we use Polymerization
- soft-start polimerization
- 1mm distance must be maintened between polymerization lamp and the surface of the filling
- Do not block the path of light- e.g. sectional matrix
- The end of the light guide should be clean
- The polymerization time depends on the lamp power
- Halogen polimerization lamp: 400-800 mW - 40sec
- Led polimerization lamp: 850-1200 mW- 15-20 sec
Explain Direction of polymerization light
- polymerization of large fillings should be performed in several steps
- polymerization light must first take place from the direction of the cavity wall through the dental structure
- the direction of light must be perpendicular to the filling surface
How does polymerization shrinkage occur?
During the polymerization of the composite, polymerization shrinkage occurs (1,5%)
What are Consequences of polymerization shrinkage?
- Marginal gap
- Enamel crackings
- Cracks in the filling
- Marginal discoloration, secondary caries
- Postoperative sensitivity
How to reduce polymerization shrinkage?
- Stress breaking liner to the pulpal wall (e.g.:flowable composite)
- Layering technique
- ‘soft-start’ polimerization mode
- polymerization light must first take place from the direction of the cavity wall through the dental structure
