Composite and acid etching

1. Composite ResinsComposite Resins
Dr.Shahbaz Ahmed
BDS, MSc (UK), FCPS (Pak)
Assistant Professor
Department of Operative Dentistry
DIKIOHS

2. Overview
• Direct restoratives
– Composition
– Classification
– Performance factors
• Forms
- Flowable
- Packables

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. 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. 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. Indications
• Anterior restorations
• Posterior restorations
– preventive resin
– conservative class 1 or 2
– cuspal coverage
– core Build up- materials

7. Contraindications
• Large posterior
restorations
• Bruxism
• Poor isolation

8. Advantages
• Esthetics
• Conservation of tooth structure
• Adhesion to tooth structure
• Low thermal conductivity
• Alternative to amalgam

9. Disadvantages
• Technique sensitivity
• Polymerization shrinkage
– marginal leakage
– secondary caries
– postoperative sensitivity
• Decreased wear resistance

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. 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. 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. Monomers
• Shrinkage
– 2 – 7 %
– marginal gap
formation

14. Filler Particles
• Crystalline quartz
– larger particles
– not polishable
• Silica glass
– barium
– strontium
– Lithium
- Polishable

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. 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. Inhibitors
• Prevents spontaneous
polymer formation
• Extends shelf life
• Butylated Hydroxytoluene

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. 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. Polymerization
• Initiation
– production of reactive free radicals
• typically with light for restorative materials
• Propagation
– hundreds of monomer units
– polymer network
• Termination

21. Classification System
• Matrix composition
• Method of cure
• Filler content
• Filler particle size
– traditional ( macrofilled)
– microfilled
– small particle
– hybrid

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. 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. Performance Factors
• Material factors
– biocompatibility
– polymerization shrinkage
– wear resistance
– polish mechanisms
– placement types
– mechanical & physical properties

25. Biocompatibility
• Tolerated by pulp
– with good seal
• Rare allergic reactions
– HEMA
• Cytotoxicity
– short lived
• Degree of cure important
– decrease free monomer

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. Polymerization Shrinkage
• Significant role in restoration failure
– gap formation
• secondary caries formation
• marginal leakage
• post-operative sensitivity
• Counteract
– lower shrinkage composites
– incremental placement

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. Polish Mechanisms
• Acquired polish
– clinician induced
• Inherent polish
– ultimate surface

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. Composite Selection
• Posterior composites
–hybrid
• mini- or midi-fill
–reinforced microfill

32. Composite Variants
• Packable
• Flowable

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. Flowable Composites
• Marketed
– class 1, 3, 5
– liner
• Particle size similar to hybrid composites
• Reduced filler content
– reduces viscosity

35. Flowable Composites
• Clinical applications
– preventive resin restorations
– small Class 5
– provisional repair
– composite repair
– Liners ??

36. Future Composites
• Low-shrinking monomers
• Self-adhesive ?

37. Composite Curing
• Original composites (Chemical cured)
• UV- Light curing
• Visible light curing
- “ Dual curing”

38. Light curing
• Quartz- Tungsten Halogen (QTH)
• Light- emitting diode (LED)
• Plasma Arc
• Laser

39. Light Curing variables

40. Curing equipment factors
• Bulb degradation
• Light reflector degradation
• Optical filter degradation
• Light guide fracture
• Tip contamination
• Sterilization problems ?
– Infection control barriers

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. 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. 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. • Pulse delay technique
• Used with final increment
• Waiting period between exposures –
shape occlusal surface
• Improved physical properties?

45. C- Factor – Cavity Configuration
C=C=
BONDED WALLSBONDED WALLS
C-FACTORC-FACTOR
UNBONDED WALLS

46. Smooth surface restoration
C=C= 11
55
C-FACTORC-FACTOR 0.20.2
BondedBonded
UnbondedUnbonded

47. Two walled cavity
C=C= 22
44
C-FACTORC-FACTOR 0.50.5
CAVITY CLASSCAVITY CLASS IVIV
BondedBonded
UnbondedUnbonded

48. Three walled cavity
C=C= 33
33
C-FACTORC-FACTOR 11
CAVITY CLASSCAVITY CLASS IIIIII
BondedBonded
UnbondedUnbonded

49. Four walled cavity
C=C= 44
22
C-FACTORC-FACTOR 22
CAVITY CLASSCAVITY CLASS IIII
BondedBonded
UnbondedUnbonded

50. Five walled cavity
C=C= 55
11
C-FACTORC-FACTOR 55
CAVITY CLASSCAVITY CLASS V & IV & I
BondedBonded
UnbondedUnbonded

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. 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. Acid Etching / ConditioningAcid Etching / Conditioning

54. History
Buonocore 1955, applied acid to teeth
‘ Render the tooth surface more
receptive to adhesion’

55. Theories of Adhesion
• Mechanical
• micromechanical interlocking
• Adsorption - chemical bonds
• Primary - ionic and covalent
• Secondary - hydrogen, van der Waals

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. 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. Etched Enamel

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. 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. Conditioned Dentine

62. Important considerations
• Kind of acid
• Application time
• Acid concentration and pH
• Distance between tubules
• Type of dentine

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. Thank You