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Composite and acid etching

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Composite and acid etching

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Composite and acid etching

  1. 1. Composite ResinsComposite Resins Dr.Shahbaz Ahmed BDS, MSc (UK), FCPS (Pak) Assistant Professor Department of Operative Dentistry DIKIOHS
  2. 2. Overview • Direct restoratives – Composition – Classification – Performance factors • Forms - Flowable - Packables
  3. 3. Composite • Material with two or more distinct substances – metals, ceramics, or polymers • Dental resin composite – soft organic-resin matrix • polymer – hard, inorganic-filler particles • glass particles • Most frequently used – esthetic-restorative material
  4. 4. History • 1871 – silicate cements – alumina-silica glass & phosphoric acid – very soluble – poor mechanical properties • 1948 – acrylic resins – polymethylmethacrylate – high polymerization shrinkage – Known as ‘Unfilled acrylics’
  5. 5. History (cont.) • 1962 – Bis-GMA – stronger resin • 1969 – filled composite resin – improved mechanical properties – less shrinkage – paste/paste system • 1970’s – acid etching and microfills • 1980’s – light curing and hybrids • 1990’s – flowables and packables • 2000’s – nanofills
  6. 6. Indications • Anterior restorations • Posterior restorations – preventive resin – conservative class 1 or 2 – cuspal coverage – core Build up- materials
  7. 7. Contraindications • Large posterior restorations • Bruxism • Poor isolation
  8. 8. Advantages • Esthetics • Conservation of tooth structure • Adhesion to tooth structure • Low thermal conductivity • Alternative to amalgam
  9. 9. Disadvantages • Technique sensitivity • Polymerization shrinkage – marginal leakage – secondary caries – postoperative sensitivity • Decreased wear resistance
  10. 10. Composition • Resin matrix – Monomer – initiator – inhibitors – pigments • Inorganic filler – glass – quartz – colloidal silica • Coupling Agent - Silane agent OCH2CHCH2O-C-C=CH2CH2=C-C-O-CH2CH-CH2O -C- CH3 CH3 CH3 CH3OH OH O O Bis-GMA
  11. 11. Monomers • Binds filler particles together • Provides “workability” • Typical monomers – Bisphenol A glycidyl methacrylate (Bis-GMA) – Urethane dimethacrylate (UEDMA) – Triethylene glycol dimethacrylate (TEGMA) Lower viscosity Diluent CH2=C-C-O-CH2CH2-O-C-NHCH2CH2CHCH2-C-CH2-NH-C- CH3 CH3 OCH2CH2O-C-C=CH2 CH3 O OOO CH3 CH3 OCH2CHCH2O-C-C=CH2CH2=C-C-O-CH2CH-CH2O -C- CH3 CH3 CH3 CH3OH OH O O CH2=C-C-O-CH2CH2-OCH2CH2 CH3 OCH2CH2O-C-C=CH2 CH3 O O
  12. 12. Monomers • Bis-GMA – extremely viscous – lowered by adding TEGDMA • freely movable • increases polymer conversion • increases crosslinking • increases shrinkage CH2=C-C-O-CH2CH-CH2O -C- OCH2CHCH2O-C-C=CH2 CH3 CH3 CH3 CH3OH OH O O
  13. 13. Monomers • Shrinkage – 2 – 7 % – marginal gap formation
  14. 14. Filler Particles • Crystalline quartz – larger particles – not polishable • Silica glass – barium – strontium – Lithium - Polishable
  15. 15. Filler Particles • Increase fillers, increase mechanical properties – strength – abrasion resistance – esthetics – handling 0 0.5 1 1.5 2 FractureToughness 0 28 37 48 53 62 % Filler Volume
  16. 16. Coupling Agent • Chemical bond – filler particle - resin matrix • Organosilane (bifunctional molecule) – siloxane end bonds to hydroxyl groups on filler – methacrylate end polymerizes with resin CH3-C-C-O-CH2-CH2-CH2-Si-OH CH2 O OH OH Bonds with filler Silane Bis-GMA Bonds with resin
  17. 17. Inhibitors • Prevents spontaneous polymer formation • Extends shelf life • Butylated Hydroxytoluene
  18. 18. Pigments and UV Absorbers • Pigments – metal oxides • provide shading and opacity • titanium and aluminum oxides • UV absorbers – prevent discoloration – acts like a “sunscreen” • Benzophenone
  19. 19. Visible-Light Activation • Camphorquinone – most common photoinitiator • absorbs blue light – 400 – 500 nm range • Initiator reacts with amine activator • Forms free radicals • Initiates addition polymerization OCH2CHCH2O-C-C=CH2CH2=C-C-O-CH2CH-CH2O -C- CH3 CH3 CH3 CH3OH OH O O Bis-GMA
  20. 20. Polymerization • Initiation – production of reactive free radicals • typically with light for restorative materials • Propagation – hundreds of monomer units – polymer network • Termination
  21. 21. Classification System • Matrix composition • Method of cure • Filler content • Filler particle size – traditional ( macrofilled) – microfilled – small particle – hybrid
  22. 22. Newer Classification System • Based on particle size – megafill • 0.5–2 millimeters – macrofill • 10–100 microns – midifill • 1–10 microns – minifill • 0.1–1 microns – microfill • 0.01–0.1 microns – nanofill • 0.005–0.01 microns • Most new systems – minifillers • Newest trend – nanofillers
  23. 23. Nanofilled Composite • Filtek Supreme (3M ESPE) • Filler particles – filled: 78% wgt – nanomers • 0.02 – 0.07 microns – nanocluster • act as single unit – 0.6 – 1.4 microns
  24. 24. Performance Factors • Material factors – biocompatibility – polymerization shrinkage – wear resistance – polish mechanisms – placement types – mechanical & physical properties
  25. 25. Biocompatibility • Tolerated by pulp – with good seal • Rare allergic reactions – HEMA • Cytotoxicity – short lived • Degree of cure important – decrease free monomer
  26. 26. Systemic • Estrogenic effects seen in cell cultures – impurities in Bis-GMA-based resins • Bis-phenol A in sealants – Olea, EHP 1996 – however, insignificant short-term risk • literature review – Soderholm, JADA 1999
  27. 27. Polymerization Shrinkage • Significant role in restoration failure – gap formation • secondary caries formation • marginal leakage • post-operative sensitivity • Counteract – lower shrinkage composites – incremental placement
  28. 28. Composite Wear • Less wear – small particle size • less abrasion – heavier filled • less attrition – non-contact areas • 3 - 5 times less – less surface area – anterior location • premolars vs. molars
  29. 29. Polish Mechanisms • Acquired polish – clinician induced • Inherent polish – ultimate surface
  30. 30. Composite Selection • Anterior/stress (Class 4) – hybrid • mini- or midi-fill – hybrid/microfill • Anterior/non-stress (Class 3 or 5) – hybrid • mini-fill – microfill
  31. 31. Composite Selection • Posterior composites –hybrid • mini- or midi-fill –reinforced microfill
  32. 32. Composite Variants • Packable • Flowable
  33. 33. Packable Composites • Marketed for posterior use – increase in viscosity • better proximal contacts • handle like amalgam? • Subtle alteration of filler – shape – size – particle distribution
  34. 34. Flowable Composites • Marketed – class 1, 3, 5 – liner • Particle size similar to hybrid composites • Reduced filler content – reduces viscosity
  35. 35. Flowable Composites • Clinical applications – preventive resin restorations – small Class 5 – provisional repair – composite repair – Liners ??
  36. 36. Future Composites • Low-shrinking monomers • Self-adhesive ?
  37. 37. Composite Curing • Original composites (Chemical cured) • UV- Light curing • Visible light curing - “ Dual curing”
  38. 38. Light curing • Quartz- Tungsten Halogen (QTH) • Light- emitting diode (LED) • Plasma Arc • Laser
  39. 39. Light Curing variables
  40. 40. Curing equipment factors • Bulb degradation • Light reflector degradation • Optical filter degradation • Light guide fracture • Tip contamination • Sterilization problems ? – Infection control barriers
  41. 41. Procedural factors • Light tip direction - adjacent to the surface • Access to restoration – light transmitting wedges • Distance from surface – 1-2mm ideally • Size of tip • Tip movement • Time of exposure – minimum of 20 secs
  42. 42. Restoration factors • Restoration thickness – 1.5 to 2mm incrementally • Cavity design – C Factor • Filler amount – scatter light • Restoration shade – darker shades decrease depth of cure – 1mm increment, Increase curing time __ “ Post Curing”
  43. 43. Curing methods • Stepped or Soft start - Start at low intensity 2-10 seconds and later increase intensity - Decreases stress, marginal leakage and fewer gaps - Increases mechanical properties - Controversial ?
  44. 44. • Pulse delay technique • Used with final increment • Waiting period between exposures – shape occlusal surface • Improved physical properties?
  45. 45. C- Factor – Cavity Configuration C=C= BONDED WALLSBONDED WALLS C-FACTORC-FACTOR UNBONDED WALLS
  46. 46. Smooth surface restoration C=C= 11 55 C-FACTORC-FACTOR 0.20.2 BondedBonded UnbondedUnbonded
  47. 47. Two walled cavity C=C= 22 44 C-FACTORC-FACTOR 0.50.5 CAVITY CLASSCAVITY CLASS IVIV BondedBonded UnbondedUnbonded
  48. 48. Three walled cavity C=C= 33 33 C-FACTORC-FACTOR 11 CAVITY CLASSCAVITY CLASS IIIIII BondedBonded UnbondedUnbonded
  49. 49. Four walled cavity C=C= 44 22 C-FACTORC-FACTOR 22 CAVITY CLASSCAVITY CLASS IIII BondedBonded UnbondedUnbonded
  50. 50. Five walled cavity C=C= 55 11 C-FACTORC-FACTOR 55 CAVITY CLASSCAVITY CLASS V & IV & I BondedBonded UnbondedUnbonded
  51. 51. C-Factor • Increasing C-Factor increases the shrinkage stress loading on the tooth-resin interface leading to de-bonding • Once failure occurs, post insertion sensitivity and recurrent caries can become a problem • C-Factor problem is a consequence of resin chemistry
  52. 52. Possible solutions • Don’t cut G.V.Black style cavity preps • Bonded base or Sandwich techniqueBonded base or Sandwich technique • Incremental placementIncremental placement • Restoration sectioningRestoration sectioning
  53. 53. Acid Etching / ConditioningAcid Etching / Conditioning
  54. 54. History Buonocore 1955, applied acid to teeth ‘ Render the tooth surface more receptive to adhesion’
  55. 55. Theories of Adhesion • Mechanical • micromechanical interlocking • Adsorption - chemical bonds • Primary - ionic and covalent • Secondary - hydrogen, van der Waals
  56. 56. Acid Etchants / Conditioners • Citric acid • lactic acid • Maleic acid • EDTA • Phosphoric acid - a strong inorganic acid (30% - 50%) most commonly used for etching
  57. 57. Conditioning Enamel • Removes 10 microns of surface and creates microporous layer • Three etching patterns - Type I – Core etching - Type II – Periphery etching - Type III – Mixed patterns • Resin tags - Macrotags - Microtags
  58. 58. Etched Enamel
  59. 59. Important considerations • Type of acid • Acid Concentration • Etching time • Form of etchant • Enamel instrumented prior • Condition of enamel • Primary or permanent enamel • Prism or prismless enamel
  60. 60. Conditioning Dentine • Chemical alteration of dentine • Objective is to remove the smear layer • Demineralizing the dentine to expose a microporous scaffold of collagen fibrils (Hybrid layer)
  61. 61. Conditioned Dentine
  62. 62. Important considerations • Kind of acid • Application time • Acid concentration and pH • Distance between tubules • Type of dentine
  63. 63. Acid Etching • Enamel • Selective Demineralization • Increases surface area • Increases life of composite • Decreases marginal staining • Decreases secondary caries • Decreases post-operative sensitivity • Permits efficient wetting by hydrophobic resin • Tag formation in microporosities • Dentine • Demineralizes dentine surface • Opens dentinal tubules • Exposes collagen • Conditions dentine for better wetting of the primer
  64. 64. Thank You

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