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DENTAL COMPOSITE.ppt - DENTAL COMPOSITES

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					DENTAL COMPOSITES

      REVIEW
DEFINITION
     COMPOSITE CHEMISTRY
• Dental composite is composed of a resin matrix and filler materials.
• Coupling agents are used to improve adherence of resin to filler
  surfaces.
• Activation systems including heat, chemical and photochemical
  initiate polymerization.
• Plasticizers are solvents that contain catalysts for mixture into resin.
• Monomer, a single molecule, is joined together to form a polymer, a
  long chain of monomers.
• Physical characteristics improve by combining more than one type
  of monomer and are referred to as a copolymer.
• Cross linking monomers join long chain polymers together along the
  chain and improve strength.
            RESIN MATERIALS
• BIS-GMA resin is the base for composite. In the late 1950's, Bowen
  mixed bisphenol A and glycidylmethacrylate thinned with TEGDMA
  (triethylene glycol dimethacrylate) to form the first BIS-GMA
  resin. Diluents are added to increase flow and handling
  characteristics or provide cross linking for improved
  strength. Common examples are:
• RESIN:-       BIS-GMA       bisphenol glycidylmethacrylate

• DILUENTS:- MMA     methylmethacrylate
             BIS-DMA bisphenol dimethacrylate
             UDMA    urethane dimethacrylate
• CROSS LINK DILUENTS
             TEGDMA triethylene glycol dimethacrylate
             EGDMA    ethylene glycol dimethacrylate
             COUPLING AGENTS
• Coupling agents are used to improve adherence of resin to filler
  surfaces.
• Coupling agents chemically coat filler surfaces and increase
  strength.
• Silanes have been used to coat fillers for over fifty years in industrial
  plastics and later in dental fillers. Today, they are still state of the
  art.
• Silanes have disadvantages. They age quickly in a bottle and
  become ineffective. Silanes are sensitive to water so the silane filler
  bond breaks down with moisture.
• Water absorbed into composites results in hydrolysis of the silane
  bond and eventual filler loss.
• Common silane agents are:
  vinyl triethoxysilane
  methacryloxypropyltrimethoxysilane
                HEAT CATALYST
• Polymerization of resin requires initiation by a free radical.
• Initiation starts propagation or continued joining of molecules at
  double bonds until termination is reached.
• Heat applied to initiators breaks down chemical structure to produce
  free radicals, however, monomers may polymerize when heat is
  applied even without initiators.
• Resins require stabilizers to avoid spontaneous
  polymerization. Stabilizers are also used to control the reaction of
  activators and resin mixtures.
• Hydroquinone is most commonly used as a stabilizer.
• Common heat based initiators are peroxides such as
  benzoylperoxide
  t-butylperoxide
  t-cumythydroxyperoxide
   PHOTOCHEMICAL CATALYST
• Early photochemical systems used were benzoin methyl ether which
  is sensitive to UV wavelengths at 365 nm. UV systems had limited
  use as depth of cure was limited. Visible light activation of diketones
  is the preferred photochemical systems. Diketones activate by
  visible, blue light to produce slow reactions. Amines are added to
  accelerate curing time.
• Presently, different composites use different photochemical
  systems. These systems are activated by different wavelengths of
  light. In addition, different curing lights produce various ranges of
  wavelengths that might not match composite activation
  wavelengths. This can result in no cure or partial cure. Composite
  materials must be matched to curing lights.
• Common photochemical initiators are:
  Camphoroquinone
  Acenaphthene quinone
  Benzyl
                 LIGHT CURING
• Light curing can be accomplished with:-
       1) Quartz-Tungsten-Halogen
       2) Plasma Arc Curing
       3) Light Emitting Diode
        CHEMICAL CATALYST
• Chemical activation of peroxides produces free radicals. Chemical
  accelerators are often not color stable and have been improved for
  this reason.
• The term self cure or dual cure (when combined with photo chemical
  initiation) describes chemical cure materials.
• Chemical composites mix a base paste and a catalyst paste for self
  cure.
• Bonding agents mix two liquids.
• Mixing two pastes incorporates air into the composite.
• Oxygen inhibits curing resulting in a weaker restoration.
• Chemical accelerators include:
  Dimethyl p-toludine
  N,N-bis(hydroxy-lower-alkyl)-3,5-xylidine
            COMPOSITE FILLERS
• Fillers are placed in dental composites to reduce shrinkage upon
  curing.
• Physical properties of composite are improved by fillers, however,
  composite characteristics change based on filler material, surface,
  size, load, shape, surface modifiers, optical index, filler load and size
  distribution.
• Materials such as strontium glass, barium glass, quartz, borosilicate
  glass, ceramic, silica, prepolymerized resin, or the like are used.
   FILLERS CLASSIFICATION
• Fillers are classified by material, shape and size.
• Fillers are irregular or spherical in shape depending on the mode of
  manufacture.
• Spherical particles are easier to incorporate into a resin mix and to
  fill more space leaving less resin.
• One size spherical particle occupies a certain space.
• Adding smaller particles fills the space between the larger particles
  to take up more space.
• There is less resin remaining and therefore, less shrinkage on curing
  the more size particles used in proper distribution.
   FILLERS CLASSIFICATION
• Classification According to Size:-
  MACROFILLERS ---- 10    TO 100 um
  MIDIFILLERS  ----- 1    TO 10 um
  MINIFILLERS  ----- 0.1 TO 1 um
  MICROFILLERS ----- 0.01 TO 0.1 um
  NANOFILLERS ----- 0.005 TO 0.01 um
                  PLASTICIZERS
• Dental composite is composed of a resin matrix and filler materials.
• Coupling agents are used to improve adherence of resin to filler
  surfaces.
• Plasticizers are solvents that contain catalysts for mixture into resin.
• They need to be non reactive to the catalyst & resin.
       Physical Characteristics
•   Following are the imp physical properties:-
•   1) Linear coefficient of thermal expansion (LCTE)
•   2) Water Absorption
•   3) Wear resistance
•   4) Surface texture
•   5) Radiopacity
•   6) Modulus of elasticity
•   7) Solubility
                      C- FACTOR
• It is the ratio of the bonded surfaces to the unbonded or free
  surfaces in a tooth preparation.
• The higher the C-Factor, greater is the potential for bond disruption
  from polymerisation effects.
         INTERNAL STRESSES
• Internal stresses can be reduced by,
  1) ‘Self start’ Polymerisation
  2) Incremental placement
  3) Use of stress breaking liners such as:-
                  a)Filled Dentinal Adhesives
                  b)RMGI.
  COMPOSITE CLASSIFICATION
• Composite is classified by initiation techniques, filler size, and
  viscosity.
• Laboratory heat process fillings are processed under nitrogen and
  pressure to produce a more thorough cure.
• Core build up materials are commonly self cure.
• Dual cure composite is commonly used as a cementing medium
  under crowns.
• Viscosity determines flow characteristics during placement. A
  flowable composite flows like liquid or a loose gel. A packable
  composite is firm and hard to displace.
    Composite is classified by initiation
    techniques, filler size, and viscosity
• Heat cured composites are polymerized by application of heat.
• Self cured composite means chemical initiation converting monomer
  to polymer takes place.
• Light cured composite means photochemical initiation causes
  polymerization
• Dual cure means chemical initiation is used and combined with
  photochemical initiation so either and both techniques polymerize
  composite.
                    Radiospacity
• One of the requirements of using a composite as a posterior
  restorative is that it should be radiopaque.
• In order for a material to be described as being radiopaque, the
  International Standard Organization (ISO) specifies that it should
  have radiopacity equivalent to 1 mm of aluminium, which is
  approximately equal to natural tooth dentine.
• However, there has been a move to increase the radiopacity to be
  equivalent to 2 mm of aluminium, which is approximately equal to
  natural tooth enamel.
• A majority of the composites described as all-purpose or universal
  have levels of radiopacity greater than 2 mm of aluminium
                     INDICATIONS
•   1) Class-I, II, III, IV, V & VI restorations.
•   2) Foundations or core buildups.
•   3) Sealant & Preventive resin restorations.
•   4) Esthetic enhancement procedures.
•   5) Luting
•   6) Temporary restorations
•   7) Periodontal splinting.
          CONTRAINDICATIONS
•   1) Inability to isolate the site.
•   2) Excessive masticatory forces.
•   3) Restorations extending to the root surfaces.
•   4) Other operator errors.
                   ADVANTAGES
•   1) Esthetics
•   2) Conservative tooth preparation.
•   3) Insulative.
•   4) Bonded to the tooth structure.
•   5) repairable.
              DISADVANTAGES
• 1) May result in gap formation when restoration extends to the root
  surface.
• 2) Technique sensitive.
• 3) Expensive
• 4) May exhibit more occlusal wear in areas of higher stresses.
• 5) Higher linear coefficient of thermal expansion.
            STEPS IN COMPOSITE
               RESTORATION
•   1) Local anaesthesia.
•   2) Preparation of the operating site.
•   3) Shade selection
•   4) Isolation of the operating site.
•   5) Tooth preparation.
•   6) preliminary steps of enamel and dentin bonding.
•   7) Matrix placement.
•   8) Inserting the composite.
•   9) Contouring the composite.
•   10) polishing the composite.
      PRINCIPLES OF ANTERIOR
      COMPOSITE RESTORATION
•   1. Smile Design
•   2. Color and Color Analysis
•   3. Tooth Color
•   4. Tooth Shape
•   5. Tooth Position
•   6. Esthetic Goals
•   7. Composite Selection
•   8. Tooth Preparation
•   9. Bonding Techniques
•   10. Composite Placement
•   11. Composite Sculpture and
•   12. Composite Polishing to properly restore anterior teeth with
    composite:
                 1. SMILE DESIGN
• A dentist must understand proper smile design so composite
  restoration can achieve a beautiful smile. This is true for extensive
  veneering and small restorations.
• Factors which are considered in smile design include:-
  A. Smile Form which includes size in relation to the face, size of one
  tooth to another, gingival contours to the upper lip line, incisal edges
  overall to the lower lip line, arch position, teeth shape and size,
  perspective, and midline.
  B. Teeth Form which includes understanding long axis, incisal edge,
  surface contours, line angles, contact areas, embrasure form, height
  of contour, surface texture, characterization, and tissue contours
  within an overall smile design.
  C. Tooth Color of gingival, middle, incisal, and interproximal areas
  and the intricacies of characterization within an overall smile design.
       2. COLOUR AND COLOUR
              ANALYSIS
• Colour is a study in and of itself. In dentistry, the effect of enamel
  rods, surface contours, surface textures, dentinal light absorption,
  etc. on light transmission and reflection is difficult to understand and
  even more difficult replicate.
• The intricacies of understanding matching and replicating hue,
  chroma, value, translucency, florescence; light transmission,
  reflection and refraction to that of a natural tooth under various light
  sources is essential but far beyond the scope of this article.
            3. TOOTH COLOUR
• Analysis of colour variation within teeth is improved by an
  understanding of how teeth produce color variation.
• Enamel is prismatic and translucent which results in a blue gray
  color on the incisal edge, interproximal areas and areas of increased
  thickness at the junction of lobe formations.
• The gingival third of a tooth appears darker as enamel thins and
  dentin shows through.
• Color deviation, such as craze lines or hypocalcifications, within
  dentin or enamel can cause further color variation.
• Aging has a profound effect on color caused by internal or external
  staining, enamel wear and cracking, caries, acute trauma and
  dentistry.
                 4. TOOTH SHAPE
• Understanding tooth shape requires studying dental anatomy.
• Studying anatomy of teeth requires recognition of general form,
  detail anatomy and internal anatomy.
• It is important to know ideal anatomy and anatomy as a result of
  aging, disease, trauma and wear.
• Knowledge of anatomy allows a dentist to reproduce natural teeth.
  For example, a craze line is not a straight line as often is produced
  by a dentist, but is a more irregular form guided by enamel rods.
            5. TOOTH POSITION
• Knowledge of normal position and axial tilt of teeth within a head,
  lips, and arches allows reproduction of natural beautiful smiles.
• Understanding the goals of an ideal smile and compromises from
  limitations of treatment allows realistic expectations of a dentist and
  patient.
• Often, learning about tooth position is easily done through denture
  esthetics.
• Ideal and normal variations of tooth position is emphasized in
  removable prosthetics so a denture look does not occur.
             6. ESTHETIC GOALS
• The results of esthetic dentistry are limited by limitations of ideals
  and limitations of treatment.
• Ideals of the golden proportion have been replaced by preconceived
  perceptions.
• Limitations of ideals are based on physical, environmental and
  psychological factors.
• Limitations of treatment are base on physical, financial and
  psychological factors.
   7. COMPOSITE SELECTION
• Esthetic dentistry is an art form. There are different levels of
  appreciation so individual dentists evaluate results of esthetic
  dentistry differently. Artistically dentists select composites based on
  their level of appreciation, artistic ability and knowledge of specific
  materials. Factors which influence composite selection include
• A- Restoration Strength,
• B- Wear
• C- Restoration Color
• D- Placement characteristics.
• E- Ability to use and combine opaquers and tints.
• F- Ease of shaping.
• G- Polishing characteristics.
• H- Polish and colour stability
        8. TOOTH PREPARATION
• Tooth preparation often defines restoration strength.
• Small tooth defects which receive minimal force require minimal
  tooth preparation because only bond strength is required to provide
  retention and resistance.
• In larger tooth defects where maximum forces are applied,
  mechanical retention and resistance with increased bond area can
  be required to provide adequate strength.
    9. BONDING TECHNIQUES
• Understanding techniques to bond composite to dentin and enamel
  provide strength, elimination of sensitivity and prevention of micro-
  leakage.
• Enamel bonding is a well understood science. Dentinal bonding,
  however, is constantly changing as more research is being done
  and requires constant periodic review.
• Micro-etching combined with composite bonding techniques to old
  composite, porcelain, and metal must be understood to do anterior
  composite repairs.
   10. COMPOSITE PLACEMENT
          TECHNIQUE
• Understanding techniques which allow ease of placement, minimize
  effects of shrinkage, eliminate air entrapment and prevent material
  from pulling back from tooth structure during instrumentation
  determine ultimate success or failure of a restoration.
• It is important to incorporate proper instrumentation to allow ease of
  shaping tooth anatomy and provide color variation prior to curing
  composite.
• In addition, a dentist must understand placement of various
  composite layers with varying opacities and color to replicate normal
  tooth structure.
    11. COMPOSITE SCULPTURE
• Composite sculpture of cured composite is properly done if
  appropriate use of polishing strips, burs, cups, wheels and points is
  understood.
• In addition, proper use of instrumentation maximizes esthetics and
  allows minimal heat or vibrational trauma to composite resulting in a
  long lasting restoration.
  12. COMPOSITE POLISHING
• Polishing composite to allow a smooth or textured surface shiny
  produces realistic, natural restorations.
• Proper use of polishing strips, burs, cups, wheels and points with
  water or polish pastes as required minimizes heat generation and
  vibration trauma to composite material for a long lasting restoration.
              DIRECT POSTERIOR
                 COMPOSITES
• Composites are indicated for Class 1, class 2 and class 5 defects on
  premolars and molars. Ideally, an isthmus width of less than one
  third the intercuspal distance is required.
• This requirement is balanced against forces created on remaining
  tooth structure and composite material. Forces are analyzed by
  direction, frequency, duration and intensity. High force occurs with
  low angle cases, in molar areas, with strong muscles, point contacts
  and parafunctional forces such as grinding and biting finger nails.
• Composite is strongest in compressive strength and weakest in
  shear, tensile and modulus of elasticity strengths. Controlling forces
  by preparation design and occlusal contacts can be critical to
  restorative success.
• Failure of a restoration occurs if composite fractures, tooth fractures,
  composite debonds from tooth structure or micro-leakage and
  subsequent caries occurs. A common area of failure is direct point
  contact by sharp opposing cusps. Enameloplasty that creates a
  three point contact in fossa or flat contacts is often indicated.
• Tooth preparation requires adequate access to remove caries,
  removal of caries, elimination of weak tooth structure that could
  fracture, beveling of enamel to maximize enamel bond strength, and
  extension into defective areas such as stained grooves and
  decalcified areas.
• Matrix systems are placed to contain materials within the tooth and
  form proper interproximal contours and contacts. Selection of a
  matrix system should vary depending on the situation (see web
  pages contacts and contours in this section).
• Enamel and dentin bonding is completed. Composite shrinks when
  cured so large areas must be layered to minimize negative forces.
• Generally, any area thicker than two millimeters requires layering.
  In addition, cavity preparation produces multiple wall defects.
• Composite curing when touching multiple walls creates dramatic
  stress and should be avoided.
• Composite built in layers replicate tooth structure by placing dentin
  layers first and then enamel layers.
• Final contouring with hand instruments is ideal to minimize the
  trauma of shaping with burs.
• Matrix systems are removed and refined shaping and occlusal
  adjustment done with a 245 bur and a flame shaped finishing bur.
  Interproximal buccal and lingual areas are trimmed of excess with a
  flame shaped finishing bur.
• Final polish is achieved with polishing cups, points, sandpaper
  disks, and polishing paste.
           INDIRECT POSTERIOR
               COMPOSITES
• Indirect laboratory composite is indicated on teeth that required
  large restorations but have a significant amount of tooth remaining.
  It is used when a tooth defect is larger than indicated for direct
  composite and smaller than indicated for a crown. A common
  situation is fracture of a single cusp on a molar or a thin cusp on a
  bicuspid. Force analysis is critical to success as high force will
  fracture composite, tooth structure or separate bonded interfaces.
  High force is indicated on teeth furthest back in the mouth for
  example, a second molar receives five times more force than a
  bicuspid. Orthodontic low angle cases and large masseter muscles
  generate high force. Sharp point contacts from opposing teeth
  create immense force and are often altered with enameloplasty.
• Indirect composite restorations are processed in a laboratory under
  heat, pressure and nitrogen to produce a more thorough composite
  cure. Pressure and heat increase cure while nitrogen eliminates
  oxygen that inhibits cure. Increased cure results in stronger
  restorations. Strength of laboratory processed composite is
  between composite and crown strength and requires adequate tooth
  support.
        TOOTH PREPARATION
• Tooth preparation requires removal of existing restorations and
  caries. Thin cusps and enamel are removed in combination of
  blocking out undercuts with composite, glass ionomer, flowable
  composite or the like.
• Tooth preparation requires adequate wall divergence to bond and
  cement the restoration and ideally, margins should finish in enamel.
  The restoration floor is bonded and light cured.
• Bonding agent is light cured to stabilize collagen fibers and avoid
  collapse during restoration placement. A base of glass ionomer or
  composite is used if thermal sensitivity is anticipated.
• Restoration retention is judged by bonded surface area, number and
  location of retentive walls, divergence of retentive walls, height to
  width ratio and restoration internal and external shape.
• Resistance form, reduction of internal stress and conversion of
  potential shear and tensile forces is accomplished by smoothing
  sharp areas and creating flat floors as opposed to external angular
  walls.
        TOOTH PREPARATION
• Impressions are taken of prepared teeth, models poured and
  composite restorations constructed at a laboratory. Temporaries are
  placed and a second appointment made.
• At a second appointment, temporaries are removed and a rubber
  dam placed. Restorations are tried on the teeth and
  adjusted. Manufacturers directions are followed. In general, bonding
  is completed on the tooth surfaces and bonding resin precured.
• Matrix bands are placed prior to etching to contain etch within
  prepared areas. Trimming of excess cement where no etching has
  occurred is easier.
• Composite surfaces are silinated and dual cure resin cement
  applied. Restorations are seated, excess resin cement is wiped
  away with a brush and then facial and lingual surfaces are light
  cured. Interproximal areas are flossed and then light cured. Excess
  is trimmed with hand instruments and finishing flame shaped burs.
• The rubber dam is removed and occlusion adjusted. Surfaces are
  finished and polished.
            COMPOSITE WEAR
• There are several mechanisms of composite wear including
  adhesive wear, abrasive wear, fatigue, and chemical wear.
• Adhesive wear is created by extremely small contacts and therefore
  extremely high forces, of two opposing surfaces. When small forces
  release, material is removed. All surfaces have microscopic
  roughness which is where extremely small contacts occur between
  opposing surfaces.
• Abrasive wear is when a rough material gouges out material on an
  opposing surface. A harder surface gouges a softer
  surface. Materials are not uniform so hard materials in a soft matrix,
  such as filler in resin, gouge resin and opposing surfaces. Fatigue
  causes wear. Constant repeated force causes substructure
  deterioration and eventual loss of surface material. Chemical wear
  occurs when environmental materials such s saliva, acids or like
  affect a surface.
       COMPOSITE FRACTURE
• Dental composite is composed of a resin matrix and filler
  materials. The resin filler interface is important for most physical
  properties.
• There are three causes of stress on this interface including: resin
  shrinkage pulls on fillers, filler modulus of elasticity is higher than
  resin, and filler thermo coefficient of expansion allows resin to
  expand more with heat. When fracture occurs, a crack propagates
  and strikes a filler particle. Resin pulls away from filler particle
  surfaces during failure. This type of failure is more difficult with
  larger particles as surface area is greater. A macrofill composite is
  stronger than a microfill composite.
• Coupling agents are used to improve adherence of resin to filler
  surfaces. Modification of filler physical structure on the surface or
  aggregating filler particles create mechanical locking to improve
  interface strength. Coupling agents chemically coat filler surfaces
  and increase strength. Silanes have been used to coat fillers for
  over fifty years in industrial plastics and later in dental fillers. Today,
  they are still state of the art.
• RECENT ADVANCES
 Multifunctional Composites and
      Novel Microstructures
• Hierarchical microstructures
• - Dr H-X Peng
• The properties of composite materials can be tailored through
  microstructural design at different lengthscales such as the micro-
  and nano-structural level.
• At the micro-structural level, our novel approach creates
  microstructures with controlled inhomogeneous reinforcement
  distributions.
• These microstructures effectively contain more than one structural
  hierarchy. This has the potential to create whole new classes of
  composite materials with superior single properties and property
  combinations.
• Research also involves tailoring the nano-structures of micro-
  wires/ribbons for macro-composites.
                   Shaped fibres
• - Dr Ian Bond, Dr Paul Weaver
• Research has shown that shaped fibres can be an effective means
  of improving the through thickness properties.
• A set of guidelines for fibre shape and a preferred ‘family’ of fibres
  have been generated from qualitative analysis for the role of
  reinforcing fibres in composites.
• Methods have also been developed to produce such shaped fibres
  from glass in order to form reinforced laminates in sufficient quantity
  for materials property testing using standard methods.
• Fibre shape has been shown to play a key role in contributing to the
  bonding force between fibre and matrix, with significant increases in
  fracture toughness possible. Results suggest that the shaped fibre
  specimens have a greater throughthickness strength than the
  circular fibre composites that are currently used.
                     Self healing
• - Dr Ian Bond
• Impact damage to composite structures can result in a drastic
  reduction in mechanical properties. Bio-inspired approach is
  adopted to effect selfhealing which can be described as mechanical,
  thermal or chemically induced damage that is autonomically
  repaired by materials already contained within the structure.
• Efforts are undergoing to manufacture and incorporate
  multifunctional hollow fibres to generate healing and vascular
  networks within both composite laminates and sandwich structures.
• The release of repair agent from these embedded storage reservoirs
  mimics the bleeding mechanism in biological organisms.
• Once cured, the healing resin provides crack arrest and recovery of
  mechanical integrity.
• It is also possible to introduce UV fluorescent dye into the resin,
  which will illuminate any damage/healing events that the structure
  has undergone, thereby simplifying the inspection process for
  subsequent permanent repair.
  Fibre Reinforced Dental Resins
• - Dr Ian Bond and Professor Daryll Jagger
• The material most commonly used in the construction of dentures is
  poly (methyl methacrylate) and although few would dispute that
  satisfactory aesthetics can be achieved with this material, in terms of
  mechanical properties it is still far from ideal.
• Over the years there have been various attempts to improve the
  mechanical properties of the resin including the search for an
  alternative material, such as nylon, the chemical modification of the
  resin through the incorporation of butadiene styrene as in the "high
  impact resins" and the incorporation of fibres such as carbon, glass
  and polyethylene.
• The use of self-healing technology within dental resins is a novel
  and exciting approach to solve the problems of the failing dental
  resins.
• Methods are currently being developed to translate the self healing
  resin technology into dental and biomaterials science.
Nanofibres and Nanocomposites
• - Dr Bo Su
• An electrospinning technique has been used to produce polymer,
  ceramic and nanocomposite nanofibres for wound addressing,
  tissue engineering and dental composites applications.
• The electrospun nanofibres have typical diameters of 100-500 nm.
  Natural biopolymers, such as alginate, chitosan, gelatin and
  collagen nanofibres, have been investigated.
• Novel nanocomposites, such as Ag nanoparticles doped alginate
  nanofibres and alginate/chitosan core-shell nanofibres, have also
  been investigated for antimicrobials and tissue engineering
  scaffolds.
• Zirconia and silica nanofibre/epoxy composites are currently under
  investigation for dental fillings and aesthetic orthodontic archwires.
               Nanocomposites
• - Dr H-X Peng
• Carbon fibre composite components are susceptible to sand and
  rain erosion as well as cutting by sharp objects.
• The use of nanomaterials in coating formulations can lead to wear-
  resistant nanocomposite coatings.
• Work is developing novel fine-particle filled polymer coating systems
  with a
• potential step-change in erosion resistance and exploring their
  application to composite propellers and blades.
• These tailored materials also have potential applications in lightning
  strike protection and de-icing.
• The nano-structure of magnetic micro-ribbons/wires is being
  investigated and optimised to obtain the Giant Magneto-Impedance
  (GMI) effect for high sensitivity magnetic sensor applications.
       Composites with Magnetic
              Function
• - Dr Ian Bond, Prof. Phil Mellor and Dr H-X Peng
• The main aim of this work is to examine methods ofincluding
  magnetic materials within a composite whilst maintaining structural
  performance.
• This has been achieved by filling hollow fibres with a suspension of
  magnetic materials after manufacture of the composite component.
• Research is continuing to tailor the magnetic properties of the
  composite to other applications.
• In another approach, magnetic microribbons and microwires are
  being tailored and embedded into macrocomposite materials to
  provide magnetic sensing functions.
                        Auxetics
• - Dr Fabrizio Scarpa
• Auxetic solids expand in all directions when pulled in only one,
  therefore exhibiting a negative Poisson’s ratio.
• New concepts are being develope for composite materials, foams
  and elastomers with auxetic characteristics for aerospace, maritime
  and ergonomics applications.
• The use of smart material technologies and negative Poisson’s ratio
  solids has also led to the development of smart auxetics for active
  sound management, vibroacoustics and structural health monitoring.
   Diamond Fibre Composites
• - Dr Paul May and Professor Mike Ashfold
• Researchers in the CVD Diamond Film Lab based in the School of
  Chemistry are investigating ways to make diamond fibre reinforced
  composites.
• The diamond fibres are made by coating thin (100 mm diameter)
  tungsten wires with a uniform coating of polycrystalline diamond
  using hot filament chemical vapour deposition.
• The diamond-coated wires are extremely stiff and rigid, and can be
  embedded into a matrix material (such as a metal or plastic) to make
  a stiff but lightweight composite material with anisotropic properties.
  Such materials may have applications in the aerospace industry.
      Novel Multifunctional Fibre
             Composites
• - Professor Steve Mann
• New types of composites with a combination of strength, toughness
  and functionality are being prepared by combining research in the
  synthesis of inorganic non-particles with that in the synthesis of
  organic polymers.
• This interdisciplinary approach has been used to produce flexible
  fibres of magnetic spider silk as shown in the photograph (left). Silk
  fibres are coated by a dipping procedure using dilute suspensions of
  inorganic nano-particles that are prepared with specific surface
  properties.
• Similar methods are being investigated with swellable polymer gels
  and bacterial supercellular fibres to produce novel hybrid
  composites.
COMPILED & PRESENTED BY,




   •Dr. Amol A.
     Khapare

				
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