بسم الله الرحمن الرحيم

DENTAL CEMENTS

Dental cements are classified according to the type of matrix

present in the set material into;

1. Phenolate

2. Phosphate

3. Polyacrylate

4. Resin (i.e. polymeric)

Another classification according to uses;

Luting cements;

Applied as a thin (25 micron) layer to bond a restoration to the tooth or to

another restorative material.

Cavity base cements;

Placed under a permanent restoration to negate some undesirable properties

e.g.: high thermal diffusivity.

Cavity lining cements;

Applied in a thin layer to seal the surface of dentine.

 

Requirements of ideal dental cements

General properties

Non toxic , non irritant

Insoluble in fluids.

Antibacterial effect.

Obtunding effect (relief of pain).

Adhere chemically to tooth.

When used as base or liner:-

•thermal, electrical, and chemical insulation.

•high mechanical properties to allow condensation of

filling without fracture.

•high modulus of elasticity to resist fracture under

masticatory forces.

When used as filling material:

Neither dissolve nor absorb oral fluids.

High mechanical properties

match teeth structure in color, translucency, and refractive index

Their coefficient of thermal expansion should match that of tooth

structure.

Low thermal diffusivity.

dimensional stable on setting.

N.B.: No single material can fulfill all of these requirements.

Zinc oxide-eugenol (ZOE) cements

It is characterized by:

*Sedative effect on the pulp (due to the presence of

eugenol)

*Neutral PH.

Forms

Powder and liquid

Ready made paste

Types of Zinc oxide-eugenol cement

Unmodified ZOE

Resin-modified ZOE

EBA-ZOE

Unmodified ZOE Composition 

Powder

Zno; is the main reactant with eugenol.

Zinc acetate; acts as accelerator

Rosin; reduces brittleness, produces cohesive mass and

reduces solubility.

Liquid

Eugenol 85% the main reactant with ZnO

Olive oil 15% improves plasticity of the cement.

Setting reactionIt is called Chelation reaction

Zno + H2o Zn(OH)2

Zn(OH)2 + eugenol Zinc eugenolate + H2o

Factors affecting setting time

Moisture: increase moisture decrease setting time

Accelerator: increase accelerator decrease setting time

P/L ratio: increase p/L decrease setting time

Temperature: increase temperature decrease setting time

MANIPULATION

Equipments

Glass slab + Stainless spatula

Zinc oxide is slowly wetted by the eugenol, therefore, prolonged

and vigorous spatulation is required, especially for a thick mix.

PROPERTIES

1-Working and setting time

It has long working time because moisture is required for setting.

Setting time is controlled by;

Moisture availability

Accelerator

Powder/liquid ratio

2-Solubility

It is highly soluble in oral fluids.

 

3-StrengthIt has low tensile and compressive strength so it is not used as

a base or cavity liner. 4-Eugenol inhibit the set of resinsSo eugenol containing cements can not be used in conjunction

with resin-based restorative materials.

5-Biocompatibility

The set cement has a PH 6-8 and has little or no effect on the pulp when

placed in deep cavities.

The presence of eugenol has an obtundent effect on the pulp and

reduces pain.

It is irritant to the pulp when it is directly contact the pulp. So, it is not

recommended when there is pulp exposure.

6-Bonding

Zinc oxide eugenol do not adhere either to tooth structure or restoration

surface. It makes mechanical retention to surface irregularities.

Uses

Temporary filling material

Temporary cementation of cast restoration

Cavity linear in deep cavity

Root canal sealer

Gingival tissue pack to displace the gingival margins before taking the

impression for crown

Surgical dressing: in which a haemostatic agent such as tannic acid is added.

 

AdvantagesZOE has obtundent effect on the pulpGood sealing ability.DisadvantagesLow strength,Low abrasion resistance,High solubility.

Resin-modified zinc oxide eugenol

To overcome the disadvantages of unmodified ZOE, the resin is added to its powder or to the liquid or both. 

FormsPowder and liquid and ready made pasteCompositionPowder-Zinc oxide-Polymethyl methacrylate-AcceleratorLiquid-Eugenol-Dissolved resins-Accelerator (acetic acid)-Thymol (antimicrobial agent)

Properties

High compressive strength

Low solubility

Uses

Permanent cementation of cast restoration

Cavity liners and base materials

Temporary filling material

4.3- Ortho-Ethoxybenzoic Acid-Alumina Modified Zinc Oxide

Eugenol (EBA-ZOE)

Powder

-Zinc oxide

-Al2o3

Polymethyl methacrylate

Liquid

EBA 66%

Eugenol 34%

Properties

Working time at room temperature is long. Setting time ranges between 7-

13 minute under oral conditions.

High compressive strength but low tensile strength

Low solubility

Uses

permanent cementation of inlays, crowns and bridges.

Base or lining material

Temporary filling

Forms

Suspension in water or organic solvent

Two-paste system (chemically cured)

One-paste system (light cured)

Composition of two paste system

Paste 1-Ca(oH)2

-Zno-Zinc stearate-Ethyl toluene-Sulphonamide

Paste 2-Glycol salicylate-Titanium oxide-Calcium sulfate-Calcium tungestate

Calcium  hydroxide  has  been  the  standard  material  for  maintaining pulp  vitality. 

Both  clinically  and  histologically.  It has  been  found  to produce  satisfactory 

results  in indirect and direct pulp capping,

 because it is capable of stimulating the formation of tertiary dentin  by  the  pulp. 

In  contact  with  vital  pulp  tissue  it  contributes  to  the  Formation of  reparative 

dentin,  a  special  variant  of  tertiary  dentin,  which  seals  exposures 

by newly formed  hard  tissue. 

Uses

Direct and indirect pulp capping

Protective liner

 

Properties

*Alkaline PH (11-12). This degree of alkalinity stimulates odontoblast cells

to produce secondary dentin

*They have antibacterial effect

*They can neutralize the free phosphoric acid of zinc phosphate cement

*Low mechanical properties

*High solubility

*Light cured type has high compressive strength

Indirect pulp capping