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
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
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
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
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
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?
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
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
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)
On the basis of this definition let us calculate and compare the c factor for different restorations. A smooth surface restoration can be a very shallow cavity on smooth surface without any definitive walls, or even a direct veneer can be an example of such a restoration.
As we move from the smooth surface restorations to five walled cavity the bonded walls are increasing and so is the c factor.
