composite Flashcards
What is the definition of an aesthetic restoration?
one that simulates the natural teeth in color, translucency, shape, size, form and contour; achieving what is known as invisible restoration that can’t be distinguished from the tooth itself.
What are the types of aesthetic tooth-coloured restorations?
- direct: resin composite, glass ionomer and hybrid materials
combine the benefits of both as resin modified glass ionomer - indirect: resin composite or ceramic inlays, onlays & veneers
What does the term composite refer to?
- a material that is composed of two or more constituents that are insoluble in each other
- this combination produces a
material with superior or intermediate properties to those of the individual constituents
What are dental resin composites?
resulted from mixing the silicate glass particles with an acrylic resin monomer
What is the composition of composites?
- orgaic resin matrix
- inorganic filler particles
- organic coupling agent
What does organic resin matrix comprises of?
- high molecular weight monomers
- low molecular weight monomers
- activator/initiator system
- inhibitors
- pigments
What are high molecular weight monomers?
- most systems are based on bisphenol glycidylmethacrylate (BisGMA) monomer, some are based on urethane dimethacrylate (UDMA) monomer and others incorporate a mixture of both BisGMA and UDMA
- both resins are extremely viscous.
What are low molecular weight monomers?
A low-viscosity monomer e.g., triethylene glycol dimethacrylate (TEGDMA) is thus added as a diluent
What are activator/initiator systems?
direct resin composite systems could be polymerized either through chemical curing (auto- or self-cure), photo-chemical through light activation or dual-cured through both mechanisms
What are inhibitors?
the inhibitor hydroquinone prevents spontaneous polymerization –>
increase shelf-life and the working time
What are pigments?
metal oxides pigments to provide different shades and opacities
Why are inorganic fillers added?
improve the strength, wear resistance and optical
characteristics of the material
What are the properties of inorganic fillers?
- decrease polymerisation shrinkage
- decrease coefficient of thermal expansion
- decrease water sorption
- increase viscosity –> decrease wetting
What is the filler particle size and loading of ideal composite?
- highly filled
- very small particles
WWhat happens if we decrease filler particle size?
increased polishability and wear resistance
What happens if filler loading is increased?
increase the mechanical
properties
What is a coupling agent?
used to bind the filler particles to the organic resin matrix
What are the advantages of resin composite?
- superior esthetic quality: their refractive index is close to that of tooth structure
- they are available in different shades to simulate all tooth colors
- satisfactory physical and mechanical properties (strength, toughness and surface hardness)
- combined with adhesives they conserve and reinforce tooth structure
- have low thermal conductivity, don’t transmit thermal shocks to pulp
- easy to repair
What are the disadvantages of resin composites?
- questionable adaptation to tooth structure
- high occlusal wear in areas of high occlusal stress
- hydrolytic Instability in the oral fluids in terms of water sorption and hydrolysis by acids
- high technique sensitivity as composite insertion is difficult and time-consuming (It needs proper isolation and attention to technique details)
- lack of anti-cariogenic potential by fluoride releas
What is the questionable adaptation found in the composite?
- high polymerization shrinkage which causes the material to pull away from the underlying enamel and dentin
- poor wettability to tooth structure because of its high viscosity and high surface tension
- high coefficient of thermal expansion than that of the tooth structure which causes marginal gap formation at the tooth restoration interface
- these shortcomings in composite cause microleakage around restoration
What are the classifications of resin composite?
- according to size of fillers
- according to curing mode (technique of polymerisatiion)
- according to packing technique
What are the types of composite according to size of fillers
- macrofilled composite (early composite)
- microfilled composite
- hybrid composite
- nano-hybrid composite
- nano composites (true nano composite)
What are macrofilled composites?
- average particle size 8-10/um and filler loading of 75-80 %wt
- non-polishable, because during polishing, the weaker organic matrix will abrade more producing a
rough surface - this type of composite is out-dated and not used anymore
What are microfilled composites?
- particle size of 0.02-0.04/um & filler loading is 35-50 %wt
- polishable, have smooth and lustrous surface, with good wear resistance due to small filler size
– low mechanical properties due to high resin content
– used in non-stress bearing areas where esthetics and smoothness of restoration is important as veneers
– their low modulus of elasticity (flexible material) makes them
suitable for cervical lesions
What are hybrid composites?
- have combination of colloidal silica microfillers and glass macrofillers
- this combination allows filler loading up to 80%wt
– they have good mechanical properties & adequate
esthetics and good surface characteristics
What are nano-hybrid composites?
- newest addition of composite filling materials
– have nanaofillers range in size from 0.005-0.01/um
– have superior esthetic and wear characteristics, high polishability,
and superior handling characteristics.
– marketed as universal composites
What are nano composites?
- its mission was to provide esthetic of microfilled resin composite and
mechanical properties of hybrid resin composite - filler loading was increased using nanoparticle and nanoclusters
What are composites classified into according to curing mode?
- chemically polymerised systems
- light-polymerised system
- dual polymerised systems
- heat polymerised systems
What do chemically polymerised systems consist of?
two-paste system: one paste
contains the activator (aromatic tertiary amine) the other paste contains an initiator (benzoyl peroxide)
What do light-polymerised systems consist of?
comprise one paste only: the paste
contains photo-sensitive chemical (camphorquinone) which absorbs
visible light to activate the benzoyl peroxide initiator
What do dual-polymerised systems consist of?
- combine both versions
- they start by photochemical reaction and continue by a chemical process
- mainly used in resin cements
What are heat-polymerised systems used for?
indirect composite
What are the advantages of visible light-cured composite?
- command setting (unlimited working time)
- no air bubbles as it is one paste (no mixing)
- improved color stability
- better control of polymerization shrinkage
What are the disadvantages of visble light-cured composite?
- direct prolonged eye exposure to light source can cause retinal damage
- heat generation from the light source could cause pulpal irritation
What is composite classified into according to packing technique?
- incremental packing
- bulk packing
What are the properties of incremental packing?
- used with light-cured composites only.
- restorations are placed in successive small increments (not more than 2mm)
- decrease polymerisation shrinkage
What are the properties of bulk packing?
- used only with chemical cured composite (historical) as it was applied as one increment
- it could be used with bulk fill composite that could be packed in 4 mm increment
- used with light cured composite, in small non deep cavities (not exceed
2mm)
What is composite classified into according to presentation?
- packable composite
- flowable composite
- bulk fill resin composite
What are the properties of packable composites?
- also named high density or condensable composites
- they are composites with high filler loading and large particle size that are used for large posterior restorations
- their packability and lack of stickiness –> tight proximal contacts
- they also have good fracture resistance
What are the disadvantages of packable composites?
- poor adaptation to cavity walls
- poor wear resistance due to large filler particles
- opaque and unesthetic for anterior restorations
What is flowable composite?
low-filled composite with low viscosity
What are the advantages of flowable composites?
- increased adaptability
- increased elasticity
What are the disadvantages of flowable composite?
- low mechanical properties as strength & wear
- high polymerization shrinkage
What are the indications of flowable composite?
in cervical lesions, in small restorations in non-stress bearing
areas, and as a liner/base under composites to absorb stresses,
also as pit & fissure sealants
What are the contraindications of flowable composite?
large restorations & in stress-bearing areas
What are the properties of bulk fill resin composite?
- it is advanced composite technology allows for directly placed posterior restorations with bulk-fill composite in a single increment (4mm)
- it may be presented as smooth and creamy consistency that can achieve high marginal adaptation to the floor and walls of the cavity
- the shrinkage stresses were decreased with decreased postoperative sensitivity, microleakage, and secondary caries.
- the light-sensitivity technology provides fast curing of 4mm in 10 seconds
What are the characteristics of resin composite used for layering technique?
- it is impossible to reproduce the lost tooth structures (enamel & dentin) with single shade of resin composite
- different shades were introduced to facilitate perfect restoration of tooth shades & all optical properties
- most of these composites are microfilled or true nano composite
What are the types of shades available?
- translucent shades
- enamel shades
- dentin shades
- body shades
- opaque shades
What is translucent hade?
- almost clear
- for creating an incisal edge and proximal line angles
What is enamel shade?
similar to enamel in translucency and modify the underlying dentin to obtain the final tooth shade
What is dentin shade?
- modify underlying tooth color
- reduce the transmission of light through the restoration
- not as opaque as masking agents
What is body shade?
- translucency is closer to the enamel shades than to the dentin shades
- used for single shade restorations (without layering)
What are opaque shades (extra white shades)?
- used to mask the dark discolorations before resin composite application
- if used improperly, it will lighten the shade of the final restoration
What are the indications of resin composite?
- can be used in all Classes of cavity preparations whether
originating from carious or non-carious lesions - used in esthetic enhancement procedures: correction of tooth form and contour (peg shape laterals), diastema closure, partial or complete veneer for discolored or defective teeth
- used as pit and fissure sealant and in preventive resin restorations (PRR)
- used as foundation or core build-up material under crowns and bridges.
- used for cementation of indirect esthetic restorations (resin cement)
- used in repair of restorations
- periodontal splinting (fixation of teeth)
- bonding of orthodontic brackets
- liner/base (flowable commposite)
What are the contraindications of resin composite?
- patients with bad oral hygiene and high caries index
- if the cavity cannot be properly isolated from oral fluids (deep subgingival areas)
- patients with heavy occlusal stresses (unfavorable occlusion or bruxism)
What are the advantages of low molecular weight monomer?
- increase fluidity for material
- decrease viscosity
- increase wettability
- improve mechanical properties
What are the disadvantages of low molecular weight monomer?
- increase polymerisation shrinkage
- increase water sorption as it is more hydrophobic
How does hydroquinoe act as an inhibitor?
neutralise free radicals
Why is there pink composite?
for gingiva during gingival recession
Hpw does coupling agent work?
- an organo-silicane is used with bi-functional molecule
- one end forms siloxane bonds (silane coupling agents) with hydroxyl group of silica filler while the other end is capable of copolymerising with monomers of matrix
Why is micro-filled composite not used in class 1 and 2?
due to stress in posterior teeth during mastication
Why is it not aesthetic to have tertiary amine in restorations?
it turns cmposite yellow
