Week4 - Composites Flashcards
what are the ways to classify composites
- filler
-handling - activation
-curing light units and concepts - properties of dental composites
what was used in 1870’s and describe
- silicate cement
- high solubility
- severe surface wear
-low mechanical properties
what was used in 1940s and describe
-PMMA
- unfilled
- high curing shrinkage
- thermal expansion and contraction
-stress at the cavity margins and severe marginal leakage
- poor wear resistance
-staining
what was used in 1960s and describe it
-composite resin
- BisGMA
- fillers bonded
- low thermal coeffeicient of expansion
- dimensional change on setting
- higher wear resistance
- improved clinical performance
what is the definition of composite
a material containing at least two components with distinct chemical and physical properties that after blended show unique and superior properties as compared to the individual componentsw
what dentin made of
collagen matrix and hydroxyapatite crystals
what are dental composites made of
organic resin matrix and inorganic filler particles
what is dental composite
tooth colored restorative material containing an organic resin matrix phase reinforced by dispersed filler particles phase bound to the resin by a silane coupling agent and an initiatory accelerator system
what are the uses and applications of composites
- tooth colored restorative material
- bonding agents
- sealants
- composite resin luting agents
- resin modified glass ionomer materials
- light activated liner materials
- CAD/CAM blocks
- resin endodontic sealers
what are the packaging types of dental composite and what is the goal of them
- protect against visible light and moisture
- plastic syringes
- unit dose capsules
- dual paste syringes
what are the components of composites
-resin matrix
- filler particles
- coupling agent
- activator- initiator system
- pigments and other components
what is in the resin matrix
-BisGMA
- UDMA
- TEGDMA
describe BisGMA and UDMA
- high molecular weight monomers- diluents necessary
- low viscosity
- low flexibilityd
describe TEGDMA
- high fluid monomer
- diluent for high molecular weight monomers ~25-30% added to Bis GMA to improve consistency for manipulation
- amount of TEGDMA = polymerization shrinkage
what is a property of the difunctional monomers of the resin matrix components
2 reactive ends to allow cross linking
what are the filler particles
- crystalline silica
- Ba
- Li
-Al silicate glass - amorphous silica
describe the filler particles
- dispersed in resin matrix
- distribution varies depending on the mateiral
- filler loading % expressed by weight or by volume
- filler size and combination
what are the benefits of filler particles
- reinforcement of resin matrix
- decreased polymerization shrinkage
- decreased thermal expansion and contraction
- viscosity control
- decreased water sorption
- increased radiopacity
what does higher filler amount affect
reduces the thermal expansion and contraction coefficients
describe what the coupling agent does
- bond between the two phases of composite
- interfacial bridge bonds the filler to the resin matrix
- better stress distribution between resin matrix and filler particles
- improves the mechanical properties
- decreased water sorption along filler- resin interface
what do monomers get converted into
polymers
what is the activator/initiator process triggered by
free radicals
what is the activator and initiator of chemical or self cure
- activator: tertiary amine
- initiator: benzoyl peroxide
what is the activator and initiator of light cured
- activator: blue light- 465 nm
- initiator: camphorquinone (photosensitizer) and DMAEMA (amine)
what does the polymerization inhibitor do
- prevent spontaneous polymerization
- stop polymerization from brief room light exposure
- once the blue light is used, all inhibitor quickly consume = polymerization chain reaction starts
- increase the shelf life of the composite resins
what are the polymerization inhibitors
- butylated hydroxytoluene (BHT)
- hydroquinone
what are the optical modifiers
- pigments: metal oxides
- opacifiers
what are the opacifiers
- titanium and aluminum oxide
- controls opacity or translucency
- comes in dentin and enamel shades
how are composites classified
- filler particle and size distribution
- handling characteristics
- type of polymerization
what are the classes of composites
- macrofill
- midifill
-microfill - hybrids: midi- micro hybrid, mini-micro hybrid, mini nano hybrid
describe macrofill and midifill composites
- not used much today
- filler size: 10-100 um (macro) and 1-10 um (midi)
- 65-70% wt%
- large fillers - rough surface finish
- not good size distribution - low wear resistance
- prone to staining
what are the brands of macrofill and midifill
-adaptic: macro
- concise: midi
describe microfill composites
-0.01-0.1 um particles
- colloidal silica 40-60% wt%
- larger filler surface area
- difficult to increase filler fraction
- too viscous
- excellent finish
- low mechanical and hardness surface properties
- use for esthetic, low stress sites: class III, layer over hybrid
what are the brands for Microfill
- durafill VS
- Epic TMPT
- Renamel
- heliomolar
describe midi-micro hybrid
- first hybrids
- mix od midid and micro fillers
- 75-80%wt
- improved surface finish
- high strength
- universal composites: anterior and posterior
what are the brands of midi-micro hybrid
- Z250
-Z100 - Herculite
-TPH
-APH - Point 4
describe mini-micro hybrid
- mix of mini and micro fillers
- 80-85% wt%
- newer material
- smoother finish thatn midi- micro hybrid
- slightly lower strength
what are the brands for mini micro hybrid
- clearfil APX
- 4 seasons
- Miris
- Vitalescence
- synergy
- Tetric
- EsthetX
describe mini nano hybrdi
- mix of mini and nano fillers
- ~80% wt
- newest materials
- strength comparable to microhybrids and finish equivalent to microfills
- not all nanocomposites contain nanofiller, filler size reported in nm
what are the brands of mini nano hybrid
-Filtek supreme ultra
- premise
- TPH3
-Simile
what are the classifications by handling characterisitcs
- regular: macrofill, microfill, hybrid, nanohybrid
- flowable
- bulk fill
describe flowable composite
- low viscocity and hybrid reduced filler
- lower filler percentage 40-60%wt, decreased modulus, increased flexibility
- adapts better without handling
- used under conventional composite at gingival floor of class II
- many are not radiopaque
what is the big issue with flowable
difficult to distinguish from recurrent caries
what is added to improve radiopacity in flowable
-barium
- strontium
- zirconium filler
describe bulk fill composite
- used to avoid incremental palcement
- highly filled with pre polymerized particles
- larger size fillers
- more translucent filler particles
- 5mm increments
- need high output lights ~1000 mW/cm^2
describe packable/condensable composite
- packable mini and midi filler greater 80%
- supposed to be handled like amalgam
- conventional hybrids have superior properties
- bulk cure inadequate
- not well accepted: fractures at marginal ridges, changes on surface texture and color match
what are the classifications by polymerization activation
- chemical cure or self cure
- light cure
- dual cure
what is the activator, initiator, advantages and disadvantages of chemical curing
- activator: aromatic tertiary amine
- initiator: benzoyl peroxide
- advantage: bulk placement
- disadvantage: mixing (bubbles, decreases strength), no control of working time, amine (not color stable)
what is the activator, initiator, advantages and disadvantages of lightcuring
- activator: blue light
- initiator: camphorquinone (~470 nm) and DMAEMA (accelerator)
- advantages: mixing not required, less porosity, increased strength. aliphatic amine (DMAEMA), more color stable than self cure aromatic tertiary amine, better control of working time
- disadvantages: limited light penetration, less than 2mm increments for 20 sec, blue light, retina damage
what is the free radical addition reaction of polymerization
- activation: activator converts initiator into a free radical
- initiation: free radical initiator starts the addition reaction
- propogation: continues polymer chain growth
- termination
visible light is:
electromagnetic radiation
what is the range of the visible light spectrum and wavelengths
- red:700-750 nm to violet:390-400nm
what is camphorquinones max absorption
468nm
what is the irradiance value
the radiant power divided by the tip area
higher the irradiance:
higher the amount of photons
what are the procedural factors for light cure
- exposure time
- tip size: smaller tip = increase output, increase heat
- distance: decrease output when you increase distance
what are the clinical/restoration factors of light cure
- darker shades absorb light
- smaller particles: increase light scatter
- curing through tooth decreases output
what are the types of curing units
- quartz- tungsten halogen (QTH)
- plasma arc
- laser
- light emitting diodes (LED)
describe QTH
- source consists of tungsten filament that is surrounded by a clear, crystalline quartx bulk containing a chlorine based halogen gas
- broad emission spectrum (~400-500nm)
- cooling system is noisy
- relatively low irradiance
- heating in the output- dont touch the tip
- retinal damage
describe the plasma arc light (PAC)
- broad emission spectrum (390-510nm)
- high radiant power and high irradiance
- PAC lights are expensive
- noisy, large, not portable, cannot be battery operated
- become less popular with the introduction of LED curing lights
decsribe the argon ion laster
- high irradiance
- 10 seconds or less compared to 40-60 with a conventional GTH source
- produces several intense and narrow emission peaks
- viable option for a high irradiance curing light that could rapidly cure dental resins
- argon- ion laters are expensive
- become less popular with LED lights
describe LED lights
- introduced in 1990s
- advantages: solid state, lightweight, battery driven, more efficient, extremely long working life
- first and second generation: relatively narrow emission spectrum
- third generation: multiwave, multipeak, polywave. ranges from 390-430nm and 440-500 nm
what are the factors that reduce light output
- degradation
- tip contamination by resin buildup - lower output
- sterilization problems- frosting the tip
- infection control barriers- need longer curing times
what are the deficient polymerization problems
- marginal staining
- increased wear
- disadaptation
- post op sensitivity
- enamel microcrakcs
- secondary caries
- microleakage
- bulk fracture of the restoration
- release of chemicals
what is the oxygen inhibited layer
- ~15 microns thick, on the outer layer which facilitates addition and wetting of subsequent layers
- just cured composite may have 50% of the unreacted methacrylate groups to co polermize with the newly added material
- older restorations will fully cure over time, do not have the unreacted methacrylate groups
- repair strength will be 50% of the original restoration
describe dual cure
- both light and chemical activator/ initiator systems
- used under ceramic inlays, onlays and crowns
- composite cement= accomodates thicker areas, light may not penetrate adequately
what are the important properties of dental composute
- polyermization srhinkage and stress
- wear resistance
- surface finish
- marginal infiltration
- water sorption
- radiopacity
- color stability
what does polymerization yielding stress caused
stress occurs at the composite- tooth interfacr
stress level will vary with polymerization shrinkage depending on:
the type of restoration configuration factor, C factorw
what is C factor
bonded/ unbonded surfaces
the higher the C factor:
the higher the stress
which restoration type has highest C factor
class I
what is failure at the interface caused by
reduced by effective bonding and lower C factor
describe polymerization stress in self cure composite
- slower polymerization rate
- internal flow, compensates for shrinkage
describe polymerization shrinkage in incremental placement
- decreased C factor
- shrinkage is not reduced
- stress is reduced
what helps decrease wear resistance
- biofilm formation = bacterial acids = soften resin matrix
- higher filler amount = higher wear resistance
what does surface finish depend on
- type and size of filler
- smaller filler size = higher surface finish
describe marginal infiltration
- decreased with improvement of adhesive systems
- failure gap between tooth and composite
- secondary caries, marginal staining and fracture and post op sensitivity
describe water sorption
- lower filler amount, higher water sorption = higher expansion
- BisGMA and TEGDMA: higher sorption as compared to UDMA
what is radiopacity important do
to distinguish carious tissue and marginal adaptation, air bubbles
when is color stability affected in composite
- color change after 2-5 years
- food, smoking, beverages
