1. Dental Cements
Amalgam
Composite
Gold

2. Dental cements are widely used in dentistry:
Cavity lining: base under restorations
Luting: cementation of crowns, bridges, inlays, onlays and orthodontic brackets
Some cements are specifically formulated to be used as filling material
Certain cements are used for special purposes in endodontics, periodontics and surgery

3. Requirements of ideal cements
A- Biological properties
It should be non-toxic, non-irritant to the pulp or other dental tissues
It should be bacteriostatic
It should provide thermal insulation to the pulp
It should provide chemical protection to the pulp
It should offer electrical insulation to the pulp from galvanic effect

5. Requirements of ideal cements
B- Rheological properties and film thickness
When used as luting for cementaion, the mixed cement should have rheological properties that allow complete sealing of restoration.
It should give minimal film thickness to obtain maximum strength for adhesive junction

6. Film thickness depends on:
Powder particles size:
fine powder particles allow lower film thickness
Viscosity of the mix: powder/liquid ratio
↑ liquid ↓viscosity ↓ film thickness
Amount of pressure applied:
↑ pressure ↓ film thickness

7. Requirements of ideal cements
C- Solubility
Cements should be insoluble in saliva and liquids taken into the mouth because:
Solubility marginal leakage, loosening of restoration and recurrent caries

8. Requirements of ideal cements
D- Mechanical properties
Depends on the intended application.
If cement used as a base under amalgam, it should have sufficient strength to withstand amalgam condensation.
Strength depends on:
Chemical composition
Powder/liquid ratio

9. Requirements of ideal cements
E- Bonding
Cements are usually bond to tooth structure and restorations by either mechanical interlocking or chemical bonding.
Cements that offer chemical bonding are described as Adhesive
Ideal dental cement should bond to tooth structure and restoration but not to instruments

10. Requirements of ideal cements
F- Optical properties
It depends on the intended purpose of application.
If cement is used for cementation of translucent restoration, only translucent cement can be used

11. Classification of cements
Oil-based cements
Zinc oxide eugenol cement (ZOE)
Non-eugenol cement
Acid-based cements
Zinc phosphate cement (ZPH)
Zinc polycarboxylate cement (ZPC)
Water-based cements
Resin-based cements

12. Zinc oxide eugenol cement
Available in two forms
Powder & liquid form:
Powder: zinc oxide (main constituent), magnesium oxide (10%), zinc acetate & zinc stearate as accelerator
Liquid: eugenol, olive oil (15%)
Ready made paste: used
as temporary filling and set
only when it comes in
contact with water

13. Setting reaction It is a chelation reaction
Zinc oxide reacts with eugenol in the presence of water to form zinc eugenolate
The set material cinsist of unreacted zinc oxide and free eugenol held in zinc eugenolate matrix
Presence of water is essential for setting
Temperature and humidity accelerate the setting reaction

14. Manipulation

15. Properties Biological: pH is about 7.
Eugenol is bacteriostatic, and has obtundent effect (can alleviate pain and pulp irritation)
Film thickness: about 40 microns
Solubility: highly soluble in oral fluids
Strength: compressive strength about 15 Mpa
tensile strength about 5 Mpa
Bonding: bond to tooth by mechanical interlocking
Optical properties: it is opaque due to presence of unreacted zinc oxide

16. Modification of ZOE Polymer-reinforced ZOE
Powder: 80 % zinc oxide, 20 % polymethyl methacrylate
Liquid: eugenol and 10% polystyrene
Compressive strength 38 Mpa
Can be used as a base, final cementation or as temporary filling

17. Modification of ZOE EBA cement
Powder: zinc oxide, 30 % alumina to increase strength,
6% rosin and copolymers to impart plasticity and reduce brittleness
Liquid: 37.5% eugenol and 62.5% ethoxy benzoic acid (EBA)
Compressive strength 85 Mpa
Can be used as a base under amalgam, final cementation or as temporary filling

18. Modification of ZOE Rapid set ZOE
Modification of powder particles size and shape, powder/liquid ratio, and by increasing the amount of accelerators

19. Applications Temporary cementation of crown and bridges
Permanent cementaion (modified reinforced types)
Base under restorations
Temporary filling material
Surgical pack
Periodontal pack
Root canal sealer

20. ZOE is contraindicated under composite restoration or other resin based materials because it interfere with the polymerization and cause discoloration of composite

21. Non-eugenol cements Based on oils other than eugenol.
Suitable for patients with sensitivity to eugenol
Used for temporary cementation for teeth that are supposed to be covered finally by ceramic restoration (because ceramics are cemented by resin cements)

22. Zinc phosphate cement ZPH
Powder: zinc oxide (main constituent), other oxides:
Magnesium oxide: maintain white color of cement and control reactivity of powder
Silica and alumina: improve mechanical properties
Liquid: aqueous solution of phosphoric acid buffered by small amounts of zinc oxide or aluminum oxide. This allow controlling working time

23. Setting reaction Acid-base reaction
3ZnO + 2H3PO4 + H2O → Zn3(PO4)2 · 4H2O
The reaction is rapid and exothermic (release heat)

24. Manipulation
Evaporation of water from liquid → lower pH → slow down the reaction
Water gain by liquid → accelerate reaction → lower working time
Powder/liquid ratio: depend on the purpose
luting: 2.5:1
base: 3.5:1
Mixing time: sec
Setting time: usually about 5-9 min
The reaction is exothermic, heat accelerate the setting. Therefore cold glass slab and mixing over large area → increase working time

25. Properties Biological: pH freshly mixed 1.3-3.6 pH after hour 6
pH after 48 hours is neutral
Film thickness: 25 microns
Solubility: % after 24 hour immersion in water
Strength: 50% of strength after 10 min, full strength after 24 hours
compressive strength: MPa
tensile strength: 3-5 MPa
Bonding: mechanical interlocking
Optical properties: ZPH is opaque
Thermal & electrical: ZPH provides good thermal and electrical insulation → used under amalgam

26. Application Permanent cement Temporary filling
Base under metallic restoration (like amalgam)

27. Zinc polycarboxylate cement (ZPC)
Present in the following forms
1- Traditional form:
powder: zinc oxide, magnesium oxide, additives like alumina, silica, fluoride and stainless steel fibers
liquid: 30-40% aqueous solution of copolymer of polycarboxylic acid (polyacrylic acid), sodium hydroxide, tartaric acid to control setting reaction
2- Pre-proportioned capsules: for mechanical mixing
3- Water stable cement: freeze-dried
polycarboxylic acid is powdered
and added to zinc oxide powder.
The liquid will be distilled water
or diluted solution tartaric acid

28. Setting reaction
Acid-base reaction between zinc oxide and ionized copolymer of polyacrylic acid
Set cement consist of zinc polycarboxylate (polyacrylate) matrix that holds the unreacted powder particles
Setting reaction is more rapid than zinc phosphate

29. Manipulation Powder/liquid ratio: cementation 1:1 base 2:1
Mixing time: sec
Setting time: min
Plastic spatula should be used because carboxylic group of cement can react with metal spatula result in tenacious adhesion
Working time can be extended by:
Using cool glass slab
Incorporation of powder to liquid in two halves
The mixed cement should be used only as long as it still has glossy surface.
loss of gloss → initial setting

30. Properties
Biological: it is acidic but it is less irritant to the pulp than ZPH because:
Polyacrylic acid is weaker acid than phosphoric acid
Polyacrylic acid chains are too large and lack of mobility required to penetrate through dentinal tubules
Film thickness: microns
Solubility: % after 24 hours immersion in water. Less than ZPH
Strength: compressive strength: MPa
tensile strength: MPa

31. Properties Bonding: ability to bond chemically to enamel & dentin
Carboxylic group bond chemically to the calcium of the tooth
Bond strength: to enamel 8 Mpa
to dentin 2 MPa
Has high bond strength to base metal alloys
Optical properties: opaque due to unreacted zinc oxide particles

32. Applications Permanent cementation Base under restoration
Note: ZPC should not be used for temporary cementation because it bonds chemically to tooth structure

33. Glass ionomer cement (GIC)
Present in the following forms
1- Traditional form:
powder: calcium fluoroaluminosilicate glass powder. Barium glass added to give radioopacity
liquid: aqueous solution of copolymer of acrylic and itaconic acids, tartaric acid not more than 5% to increase working time & decrease setting reaction (sharp setting)
2- Pre-proportioned capsules: for mechanical mixing
3- Water stable cement: freeze-dried
polycarboxylic acid is powdered
and added to glass powder.
The liquid will be distilled water
or diluted solution tartaric acid

34. Setting reaction Acid-base reaction Three stages of setting reaction:
Dissolution: dissolution of surface of glass particles by acid releasing Ca++, Al+++ and fluoride ions
Migration: migration of ions (Ca++, Al+++ and fluoride) into liquid, Ca++ migrates first followed by Al+++ , sodium form silica gel on surface of glass particles
Reaction and precipitation: migrating Ca++ and Al+++ react with carboxylic group of acid to form cross-linked polycarboxylic salt gel
Set cement consist of unreacted glass particles surrounded by silica gel embedded in matrix of cross-linked poly salt hydrogel of calcium & aluminum

35. Properties
Biological: has mild effect on the pulp, has anticariogenic effect due to release of fluoride from set cement, fluoride recharge
Film thickness: 24 microns
Solubility: 1.5% after 24 hours immersion in water
GIC should be protected from premature exposure to water or saliva
Strength: compressive strength: MPa
tensile strength: MPa

36. Properties
Bonding: chemically bond to tooth structure by reaction of polycarboxylic group with calcium and phosphate content of tooth structure
Bond strength is lower than that of ZPC
To increase bond strength to dentin, the surface should be treated with conditioner (usually diluted polycarboxylic acid) to remove smear layer.
Optical properties: it is translucent. Can be used for cementation of all ceramic restorations, and used as esthetic restorative material for children

37. Drawbacks of conventional GIC
Initial solubility (moisture sensitivity)
Low early strength
Low abrasion resistance
Several modification were made to overcome these drawbacks

38. Modifications Metal modified GIC (cermet glass ionomer)
Fine particles of precious metals (silver, gold or palladium) are sintered with the glass ionomer powder particles, most commonly silver is added
Adv:
1) higher abrasion resistance
2) higher flexure strength
3) higher fracture toughness
Disadv:
1) more opaque than conventional GIC
2) less fluoride release
Uses:
1) core build up material
2) filling material for class I and II in primary teeth

40. Modifications
Light cure glass ionomer (resin modified glass ionomer) RMGIC
Polymerizable functional group incorporated to give more rapid curing when activated by light or chemical.
These materials set by polymerization reaction in addition to acid-base reaction that continues long after polymerization
There are two types:
Dual cure resin modified GIC
Triple cure resin modified GIC

41. Dual cure RMGIC Set by: Triple cure RMGIC
Conventional acid-base reaction: mixing powder&liquid
Polymerization reaction of resin: light curing
Triple cure RMGIC
Light cure polymerization of resin
Chemical cure polymerization of resin

42. Modifications Nano-ionomer
RMGIC that contain nano-sized fillers in a range of nm
Adv:
better esthetic
higher wear resistance
Easier polishing

43. Resin-based cements
Classified according to their bonding mechanism to tooth structure into:
Conventional resin cements
Adhesive resin cements

44. Conventional resin cement
Gain their retention through acid etching procedure in conjunction with enamel & dentin bonding agents
Self-cure resin cements
powder/liquid or two pastes of diacrylate monomer diluted to lower molecular weight dimethacrylate monomer
Light-cure resin cements
single paste of Bis-GMA or UDMA diluted to lower molecular weight monomer
Dual-cure resin cement
two paste system of material similar to light-cure but it can polymerize by two mechanisms of setting, light & chemical curing at the same time

45. Adhesive resin cement Formulated with adhesive promoter:
4 META (4 methaciyoxy ethyl trimellitic anhydride)
Phosphonate group: phosphate end of phosphonate group reacts with calcium of the tooth or with metal oxides of restoration surface

46. Properties Biological: it is irritant to the pulp
Deep areas of cavity require pulp protection with calcium hydroxide or GIC liner
Film thickness: varies from one product to another
Solubility: they are insoluble in oral fliuds
Strength:
Compressive strength: MPa
High fracture toughness compared to other cements
Bonding: mentioned previously
Optical properties: translucent

47. Other materials related to dental cements
Cavity varnish (copalite varnish)
composed of synthetic resin dissolved in organic solvent such as acetone, chloroform or ether
It is applied to the prepared cavity with brush or cotton pellet, solvent is allowed to evaporate leaving thin coating resin film on surface
This may be repeated two to three times to give uniform resin layer
Application:
Seal dentinal tubules & prevent penetration of chemicals into the pulp
Applied over glass ionomer filling to protect it from moisture in the first 24 hours
Applied under amalgam to seal the gap between amalgam and tooth until corrosion layer is formed

49. Calcium hydroxide cement (Dycal)
Supplied in either:
Two paste: chemically cured
Base: mixture of calcium hydroxide,
zinc oxide and sulfonamide
Catalyst: glycol salicylate, titanium
dioxide and calcium sulfate
Single paste: light cured

50. Properties of Ca(OH)2:
Fresh mix is highly alkaline with pH about when placed in very deep cavity, it stimulates the pulp to lay down dentin, and if applied on exposed pulp it can kill microorganisms remaining in the cavity
Solubility: it is highly soluble
Strength: very low compressive strength 5 MPa
If applied under amalgam, it should be covered with ZPH cement before condensation of amalgam, because it is very weak