Recent advances have improved dental composite materials. Composites contain resin and inorganic fillers to increase strength while decreasing problems from resin such as shrinkage. Larger filler particles improve strength but smoothness while smaller fillers enhance esthetics. Novel composites aim to reduce shrinkage through techniques like silorane resin which uses a different polymerization or bulk fill which can be placed in 4mm layers. Other trends include nano-filled composites with ultra-small particles achieving high filler loading and strength, and smart composites which release ions to prevent decay. Indirect composites can be contoured outside the mouth but still experience shrinkage during cementation. Overall composites continue advancing but shrinkage remains a challenge.

1. Recent advances in dental composite
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Fillers inside composite resin
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Fillers Resin matrix
Advantages Disadvantages
* ↑Filler amount →
↑strength & viscosity
* ↓Filler size →
↑smoothness & esthetics
* ↑ Polymerization shrinkage
(major disadv. of composite)
* ↑ Water sorption →
↑ staining (↑discoloration)

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6. Disadvantages of Conventional Composite Resin
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 Polymerization Shrinkage (major disadvantage) →
* Microleakage
* Post-operative sensitivity (pain)
* Marginal discoloration
* Recurrent caries
 Technique sensitive & time consuming (incremental placement)

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8. Notes
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 ↑ Filler loading (amount, content) → ↓ resin content → ↓ problems of resin,
such as:
* ↓ Polymerization shrinkage.
* ↓ Water sorption → ↓ Staining (↓ discoloration).
 ↑ Filler loading →
* ↑ Mechanical properties (strength, hardness, wear resistance).
* ↑ Viscosity → Improve workability (give body to the material).
 ↓ Filler size → ↑ smoothness & better esthetics.

9. Items to be covered
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* Dental cement: composite resin cement
* Restoration
1. Direct composite Restoration
- Combination between composite & GIC: Compomer & Giomer
- According to viscosity: Flowable & Packable (condensable) composite
- Ormocer
- Smart composite
- Novel trends in direct composite restorations
* Nano-filled * Silorane (low-shrink) * Bulk-fill * Cention N
2. Indirect composite restoration → Just for reading (Reading only)

10. Composite resin cement
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 The first trial to use the resin as cement was unfilled resin (without filler)
 but it showed Some drawbacks (disadvantages), such as:
* Polymerization shrinkage (due to high resin content)
* Irritation
 So, they tried to use filled composite (contains filler) as cement.
 It had high filler loading (60 wt %).
 Types: visible light cure, chemical and dual cure.

11. Composite resin cement (continued)
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a. Visible light cured (VLC) type
-There is no difference in its composition from VLC composite restoration.
- Present in different shades.
b. Dual cure composite cement
- This material has the ability to polymerize even in absence of light source.
- Indications (uses): cementation of endodontic post and ceramic inlay & crowns.
c. Chemical cured composite cement
- Initiator: benzoyl peroxide. - Activator: tertiary amine.
- Indication: Mainly used for luting (cementation) of metallic restoration
- Contains 4-META (methacryloxy ethyl trimellitic anhydrite).
- Good bond with metal restoration.

12. Composite resin cement (continued)
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GENERAL PROPERTIES (in comparison with other dental cements)
1- Good biological properties, if there is a good degree of curing →
↓ residual monomer
2- No adhesion (chemical bond) with tooth structure, but ………
3- Low degree of solubility in the oral fluids, but there are some
inhibition of polymerization caused by moisture & saliva, so it is very
important to apply air inhibition gel.
4- Good esthetic quality.
5- Good compressive and tensile strength.

13. Composite resin cement (continued)
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Note: the material of choice (the best material) for cementation
of all-ceramic (translucent) restoration is composite resin
cement, why?
 ↑ Strength & ↓ solubility
 Translucent & good esthetics
 Good bond strength

14. POLY ACID-MODIFIED COMPOSITE (COMPOMER)
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 A type of composite which is modified by application of
polyacrylic acid
 Not a glass ionomer material
 Light-cured low fluoride-releasing composite resins
 The term compomer is derived from the words
composite & glass ionomer

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Compomer (continued)
 Composition
- UDMA
- Polyacid-modified monomer = TCB (HEMA and butane carboxylic
acid)
- Strontium alumino fluorosilicate glass
- Others: initiator & pigments
 Uses
- Mainly used in low stress-bearing areas (class III & V)

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Compomer (continued)
Setting process
Compomer
Composite
resin
Glass
ionomer
Polymerization
reaction
Acid-base
reaction

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Compomer (continued)
Disadvantages
1- Fl release: lower than glass ionomer (10% of that released by glass ionomer)
- Lower amount & duration of Fl release
- No recharge from fluoride treatment [Textbook: Craig 14 ed 2019]
2- Bond: still needs etching & dentin bonding agent prior to its placement
3- Esthetic: lower than composite resin.
- Lower color stability: due to change in refractive index by
water absorption & staining [Textbook: Phillips 12 ed 2013]
4- Wear resistance: lower than composite resin

18. GIOMER
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Pre-reacted glass ionomer (PRG)
 Fluoro aluminosilicate glass reacted with polyacrylic acid prior to (before)
inclusion into the silica gel urethane resin.
 Should be classified as a light cured composite.
 Differ from compomer (give reason)
* because in giomer, the acid base reaction has already
occurred. While in compomer, ………..
 Not classified as compomer (give reason) ………

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GIOMER (PRG) [continued]
Indications (uses)
 Restoration (filling) of root caries
 Class III & V cavities
Advantages
1- Fl release & recharge
2- Biocompatible
3- Excellent esthetic
& smooth surface finish

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Flowable composite
 Flowable = has high flow …… Why??
 Low filler loading (50%) →
* ↓ viscosity & ↑ flow → [ Pit & fissure sealant ]
* ↓ modulus of elasticity & ↑ flexibility →
stress breaker (absorb stresses) → [ Liner under class I & II ]
* ↓ mechanical properties → [ Non stress-bearing areas ]
* ↑ resin amount → ↑ polymerization shrinkage

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Flowable composite
Indications (uses)
 Pit and fissure sealant ……. Why ??
 Liner under class I & II composites …….. Why??
 Class V restorations (non stress-bearing areas, not incisal & not occlusal) …… Why??
 Repair of broken restoration.

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Packable composite (condensable composite)
 Packable (condensable) = able to be packed & condensed (like amalgam) → to
produce better proximal contour & contact.
 Interlocking elongated fibers (100 μm) → causes the uncured material to:
* Resist flow (↑ viscosity)
* ↑ Stiffness of uncured material
* Resist slumping, but moldable under condensation forces
Disadvantage
 ↑ viscosity → ↑ probability of voids.

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Packable composite (condensable composite)
Notes (Phillips 12 ed 2013)
 At present, these materials have not demonstrated any advantageous
properties over the hybrid resin other than being condensable (packable).
 Despite the manufacturers’ claims, packable composites have not proven to
be an answer to the general need for:
* High wear resistance
* Easily placed
* Low polymerization shrinkage
* Depth of cure more than 2 mm

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Ormocer (organically-modified ceramics)
 Contains inorganic-organic copolymer
 Inorganic: (Si-O-Si) polysiloxane
 Organic: methacrylate groups
 3D cross-linked copolymer

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Ormocer (organically-modified ceramics)
Advantages
 Presence of inorganic part → ↓ organic part (↓ resin content).
* ↓ Organic part → ↓ polymerization shrinkage.
 Large space between cross-links → ↓ polymerization shrinkage.

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Smart composite
 Ion-releasing composite: release alkaline ions, e.g. F, Ca, OH.
 Plaque (food) accumulation (caries initiation) = ↓ pH (acidic medium) →
release of alkaline ions → buffer (neutralize) the acids (↓ acidity) →
↓ tooth decomposition (↓ tooth demineralization & decalcification).
Advantages
 Fluoride release → anticariogenic (prevent caries)
Note
 The adhesive will reduce (inhibit) the benefits of fluoride release.

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28. Novel trends in composite restoration
1. Nano-filled composite
2. Silorane (low shrinkage) composite
3. Bulk-fill composite
4. Cention N
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29. Nano-filled composite
 True nano-composite, not nano-hybrid.
 High filler loading (90 % wt), because it has:
* Nanomers: non agglomerated particles of 20-75 nm.
* Nanoclusters: loosely bound agglomerate that act as single units.
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30. Nano-filled composite
 ↑ Filler loading → * ↑ mechanical properties (surface hardness,
flexural strength & modulus of elasticity)
* ↓ resin amount → ↓ polymerization shrinkage
 ↓ Filler size (nanosize) →
* ↑ Smoothness & polishability
* Smaller than wavelength of light → no scattering
or absorption of light → ↑ translucency
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31. Shrink-free (low shrinkage) composite
Silorane resin-based composite
 Formed of siloxane & oxirane resins.
 Oxirane resin:
* Ring opening addition polymerization reaction.
* Opening the ring → gains space → compensate the shrinkage
(when the resin molecules move toward each other to form chemical bond)
→ ↓ shrinkage
→ less microleakage & better marginal integrity
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32. Shrink-free (low shrinkage) composite
Silorane resin-based composite
 Siloxane → hydrophobic → ↓ water sorption & staining (discoloration)
 Silorane needs special adhesive system for bonding, Why?
→ because it is not methacrylate-based composite.
It is silorane-based composite ……….
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34. Bulk-fill composite
 Bulk fill = bulk increment (layer, 4 mm)
 Can be placed with thickness of 4 mm instead of using
incremental placement (2 mm).
 The depth of cure is increased by:
* High translucency
* Extra initiator
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35. Bulk fill composite
 Types: packable and flowable.
 Overcomes polymerization stress by using:
* Resin: stress-relieving monomer
* Filler: special fillers with low elastic modulus
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36. Cention N
 Alkasite = contain alkaline fillers, such as
calcium fluorosilicate glass, which releases
ions (F, OH, Ca) in the presence of acidic medium
→ neutralize the acidity & prevent caries.
 A subgroup of composite
 Fluoride release: comparable to that of GIC
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37. Cention N (continued)
 Form: powder & liquid
 Self- or dual-cure: self-cure with optional additional light-cure
 Full-depth curing = Bulk-fill, Why? ……..
 Isofillers (prepolymers) → ↓ polymerization shrinkage
 Low modulus of elasticity & polym. shrinkage → ↓ polymerization stress
 It is claimed that: * It can be used as a restoration for stress-bearing areas.
* It can be applied with or without an adhesive (dentin bonding agent).
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Indirect composite restoration
An attempt to overcome the disadvantages of direct adhesive
restorations, such as:
 Polymerization shrinkage.
 Inability to obtain proper (correct) anatomical contour,
especially proximal contact.
Just for reading (Reading only)

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Indirect composite restoration(continued)
 Constructed in dental laboratory.
 Good anatomical contour & proximal contact
 The problems with polymerization shrinkage
is not totally eliminated,
→ because there is some doubt about the bond
between the resin luting cement and the
indirect composite.

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Resin-to-resin bonding
(Introduction to dental materials, p. 229)
 One might imagine that resin-to-resin bonding should be free of
problems, this is, in fact, not the case.
 In particular, there have been problems of debonding between the luting
resin & composite inlay.
 Oxygen inhibition layer does not exist.
 The luting resin has to bond directly to fully cured resins.
 This is similar to repairing a fractured composite restoration with new
composite resin.

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Resin-to-resin bonding (continued)
 Roughened by grit-blasting (alumina sandlasting).
 Phosphoric acid etching → clean the surface.
 HF acid is not recommended.
* HF causes degradation of the composite surface
by etching away the silica glass → leaving a weak
& porous polymer matrix. (Craig, p. 282)
 Tribochemical technique → silica layer, then silane
application.
Why?

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Resin-to-resin bonding (continued)
The problem of resin-to-resin bonding has not yet been
resolved satisfactorily, & thus will continue to be an area
of research interest.
(Introduction to dental materials, p. 229)

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Indirect composite restoration(continued)
Fibre-reinforced composite
 Developed as an alternative to both all-ceramic and ceramometal
restorations.
 The fibers may be:
* Made from: glass, carbon or polyethylene
* Shape: unidirectional, mesh or wave

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46. Fiber-reinforced composite (continued)
Factors affecting the degree of success of fibers
 Good bond between fibers & resin matrix
 Alignment of fibers: * should be parallel to tensile force
(not perpendicular to the force direction)
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48. Notes
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Polymerization shrinkage
& polymerization stress

50. How to ↓ polym. shrinkage or stress?
1. Filler: * ↑ filler loading → ↓ resin content → ↓ polym. shrinkage.
* Different filler size (hybrid composite) → ↑ filler loading → ……
* Prepolymers (isofillers) → ↓ polym. shrinkage.
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51. How to ↓ polym. shrinkage or stress?
2. Resin: * Silorane resin: ring-opening polymerization →
↓ polymerization shrinkage.
* Ormocer: inorganic-organic copolymer, presence of inorganic
part → ↓ organic part → ↓ polymerization shrinkage.
* Bulk fill: stress-decreasing resin → ↓ polymerization stress.
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52. How to ↓ polym. shrinkage or stress? (continued)
3. Technique: indirect composite → ↓ polym. shrinkage.
4. Placement (insertion):
* Note: bonding agent → ↓ microleakage.
* Flowable composite as a liner under class I & II →
↓ polymerization stress.
* Incremental placement (layer by layer, 2 mm)
5. Curing: soft-start polymerization (gradual, start with low light intensity)
→ ↓ polym. stress.
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53. Items that have been covered
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* Dental cement: composite resin cement
* Restoration
1. Direct composite Restoration
- Combination between composite & GIC: Compomer & Giomer
- According to viscosity: Flowable & Packable (condensable) composite
- Ormocer
- Smart composite
- Novel trends in direct composite restorations
* Nano-filled * Silorane (low-shrink) * Bulk-fill * Cention N
2. Indirect composite restoration → Just for reading (Reading only)

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References
Sakaguchi R, Ferracane J, Powers J. Craig's restorative dental materials. 14th ed. St.
Louis, Elsevier; 2019.
Anusavice KJ, Shen C, Rawls HR. Phillips' science of dental materials. 12th ed. St.
Louis, Elsevier; 2013.
Van Noort R, Barbour ME. Introduction to dental materials. 4th ed.
Mosby Elsevier; 2013.