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ZINC OXIDE EUGENOL CEMENT

Seminar By

Dr. M. SHANMUGARAJ Postgraduate Student

DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS SRI RAMACHANDRA DENTAL COLLEGE AND HOSPITALS CHENNAI. 1


CONTENTS INTRODUCTION CLASSIFICATION COMPOSITION: 1)

Zinc oxide eugenol cement

2)

Modified zinc oxide eugenol cement

3)

Polymer Reinforced zinc oxide eugenol cement

SETTING REACTION FACTORS AFFECTING SETTING TIME PROPERTIES Mechanical i)

Compressive strength

ii)

Tensile strength

iii)

Modulus of Elasticity

Thermal: i)

Thermal conductivity

ii)

Co-efficient of thermal expansion

iii)

Solubility of disintegration

Film Thickness Adhesion Viscosity Adaptability Optical Properties Biological Properties Biological compatibility and the studies related to it: MANIPULATION APPLICATION OF ZINC OXIDE EUGENOL COMPATIBILITY

OF

ZINC

OXIDE

EUGENOL

RESTORATIVE MATERIALS AND TECHNIQUES. INDICATIONS AND USES: STUDIES RELATED TO ZINC OXIDE EUGENOL COMMERCIAL NAMES 2

WITH

OTHER


INTRODUCTION Many types of cement used in dentistry can be characterized by setting reactions, which involve the formation of chelate compounds between zinc ions and orthodisubstituted aromatic compounds. 

One of the types used is; Zinc Oxide Eugenol cement.

Zinc Oxide Eugenol cement still remains the most effective Temporary filling material when prevention of pulpal injury is of prime concern. Rickert developed original cement.

Certain types of Zinc oxide eugenol cement, when mixed with eugenol sets to hard cement that are compatible with the hard and soft tissues of the mouth.

These cements have been used extensively in

dentistry since 1980’s. They are cements of low strength, also they are the least irritating of all dental cements, and are known to have an obtundant (sedative) effect on exposed dentin. Recently, non-eugenol cements have become available.

Suitable for patients sensitive to eugenol.

Experimental

vanillate and syringate cements without eugenol are presently under investigation. Eugenol, a phenol derivative is known to be toxic, and it is capable of producing thrombosis of blood vessels when applied directly to pulp tissue.

It has also aesthetic properties and is used as an

anodyne in relieving the symptoms of painful pulpitis.

This

presumably results from its ability to block the transmission of action potentials in nerve fibers.

3


CLASSIFICATION ADA SPECIFICATION NO: 30 It has listed 4 types of Zinc oxide eugenol Restorative materials. TYPE I

: ZINC OXIDE EUGENOL –

For temporary cementation.

TYPE II

: ZINC OXIDE EUGENOL –

For permanent cementation.

TYPE III

: ZINC OXIDE EUGENOL –

For Temporary filling material

and

thermal

insulation TYPE IV

: ZINC OXIDE EUGENOL –

For cavity liners. [Coating on the pulpal wall

in

provide

order

to

protection

from chemical insult from

the

material].

4

restorative


COMPOSITION I)

ZINC OXIDE EUGENOL: Powder: Zinc oxide: 69.0%

- Principal ingredient

White rosin: 29.3%

- To reduce the brittleness to set cement.

Zinc stearate: 1.0%

- Accelerator, Plasticizer.

Zinc Acetate: 0.7%

- Accelerator improves strength.

Magnesium oxide: Added in some powders, acts with eugenol in a similar manner as Zinc oxide. Liquid:

II)

Eugenol: 85.0%

- Reacts with Zinc oxide

Olive oil – 15.0%

- Plasticizer

MODIFIED ZINC OXIDE EUGENOL CEMENTS: EBA – Alumina modified cements: Powder: Zinc oxide : 70% Alumina: 30% Liquid: EBA – 62.5% Eugenol – 37.5%

III)

POLYMER RE-INFORCED ZINC OXIDE EUGENOL CEMENT: Powder: Zinc oxide; Finely divided natural or synthetic resins. Liquid: Eugenol: Acetic acid: accelerator Thymol: Antimicrobial agent 5


SETTING REACTION It involves chelation of two eugenol molecules, with one zinc ion to form Zinc eugenolate. The reaction is as follows: 1st reaction Hydrolysis of Zinc oxide to its hydroxide. Zinc oxide + H2O → Zn (OH) 2 2nd reaction Chelation: 2HE →

ZnE2 + 2H2O

(Base)

(Acid)

(Salt)

Zinc Hydroxide

Eugenol

Zn (OH)

2

+

Zinc Eugenolate

The chelate forms an amorphous gel that tends to crystallize imparting strength to the set mass. 

This reaction proceeds very slowly in the absence of the moisture. When the mixed material contacts water, however, setting is often completed within a few seconds.

Setting time: 4 – 10 minutes. Structure of the set cement: (unmodified form)

It consists of particles of Zinc oxide embedded in a matrix of particles of zinc eugenolate.

Water is needed to initiate the reaction and it is also a by-product of the reaction.

This type of reaction is often called “Auto catalytic”. 6




Free eugenol content of the set cement is probably extremely low. It appears to be much higher than it actually is, because the

chelate hydrolyzes readily, forming free eugenol and zinc ions. Structure of the set cement: (Modified form) Composed primarily of the original particles of Zinc oxide and modifiers joined with a continuous matrix of eugenol, zinc eugenolate & Zinc benzoate. (If EBA takes part in the reaction) Setting shrinkage: Zinc oxide eugenol exhibits the least amount of shrinkage of all intermediary base materials. (0.1% by volume)

FACTORS AFFECTING THE SETTING TIME The complete reaction between Zinc oxide and eugenol takes place in about 12 hrs. This is too slow for clinical convenience. 1)

Manufacture: Most

active

zinc

oxide

powders

are

those

formed

by

decomposing zinc salts like zinc hydroxide & zinc carbonate by heating at 300°C 2)

Particle Size: Cements from powders containing smaller zinc oxide particles set faster.

3)

Accelerators: The normal reactivity between Zinc oxide and eugenol is very limited and must be accelerated in order for the material to have clinical application. 7


Acceleration is achieved by: a) Incorporating chemical accelerators in the mix. b) Reducing the powder particle size. c) Increasing the powder / liquid ratio. d) Increasing the % of rosin and fillers. e) Increasing the temperature and or humidity f) Adding water to the original mix or after mixing is completes and seated into the preparation. g) Introducing Greater energy in the mixing procedure (pressure – movement and time) Chemical accelerators: 

Alcohol

Glacial acetic acid

Small amount of water

Zinc electoral

Zinc propionate

Zinc succinate.

Heat: High temperature

→ accelerates setting reaction.

Lower temperature

→ slows the reaction.(Cooling the slab)

Retarders Set can be retarded with the glycol, glycerin and vegetable oils → which keep the mass plasticized for long period of time. Powder /Liquid ratio: increasing the Powder /Liquid ratio → faster the setting reaction.

8


PROPERTIES MECHANICAL PROPERTIES 1)

Compressive strength: 

Relatively weak cements.

Unmodified Zinc oxide eugenol: 800 – 5,000 PSI

Modified Zinc oxide eugenol: 12,000 PSI

Strength is inversely proportional to the particle size of the powder.

It is directly proportional to the Powder /Liquid ratio and % of rosin, EBA and % of Filler in the mass.

Strength depends on intended use of the materials.

For e.g.: cements used for temp fillings / cementation / cavity lining Have low strength. Permanent

/

Intermediate

restoration

high

strength. 

Range of compressive strength: 3 – 4 Mpa (Low) 50 – 55 Mpa (high)

Zinc oxide eugenol is viscoelastic that is why they react more and favorably in resisting deformative failures with high rates of stressing rather than lower ones.

2)

Tensile strength: Varies according to the intended use Range: 0.32 to 5.8 Mpa

EBA – Alumina modified Zinc oxide eugenol: 4.1 Mpa (600 psi) Polymer Reinforced Zinc oxide eugenol: 4.1 Mpa (600 psi)

9


3)

Modulus of Elasticity: Important property for those cements intended for use as bases. Range:

0.22 to 5.4 GPA 0.03 to 0.79 psi

EBA – Alumina Zinc oxide eugenol: 2.5 GPA (0.36 psi * 106) Polymer Reinforced Zinc oxide eugenol: 2.5 GPA (0.36 psi * 106) THERMAL PROPERITIES 1)

Thermal Conductivity 

Thermal insulating properties are excellent

Approximately same as that of human dentin

Thermal conductivity of Zinc oxide eugenol; 3.98 (cal. sec-1 cm-2 (oc / cm>)

2)

-1

x 10-4

Co-Efficient of Thermal Expansion 

The material with the co-efficient of thermal expansion closest to the tooth structure is Zinc oxide eugenol; 11 PPM / 10c

3)

Solubility & Disintegration 

Important

for

cements

used

for

permanent

cementation. Zinc oxide eugenol: 0.04% wt EBA – Alumina Zinc oxide eugenol: 0.05 % wt Polymer reinforced Zinc oxide eugenol: 0.03% wt 

Solubility of the set cement is high (highest among the dental cements)

10


Incorporation

of

EBA

drastically

increases

the

solubility, but this can be compensated by the addition of rosin of fillers. 

Chelating acids increase the solubility 06 Zinc oxide eugenol

Solubility is directly proportional to the time. o Grater the % of original or dispersed particles bound to the matrix, less the solubility. (That is increased Powder/ Liquid ratio to the full bounding capacity 06 the liquid → decreased solubility of disintegration.

Zinc oxide eugenol disintegrates in the oral fluids.

This breakdown is due to hydrolysis of Zinc eugenolate matrix to form Zinc hydroxides and eugenol. FILM THICKNESS 

Important for those cements used for cementation of restorations.

Film thickness is higher than other cements. Zinc oxide eugenol: 25 µm EBA – Alumina modified: 25µm Polymer reinforced: R32 µm

ADHESION 

They do not adhere to enamel or dentin.

One reason why they are not often used for final cementation of dental restorations.

11


VISCOSITY 

Zinc oxide eugenol has highest flow of all materials.

Zinc oxide eugenol flow decreases by increasing the; 1)

Powder /Liquid ratio

2)

Adding fillers, rosin & EBA

ADAPTABILITY Governed by the following factors: 1)

Film thickness Lower the Film Thickness → Better its wetting ability ↓ To the irregular areas of the preparation ↓ Increase Adaptability

2)

Viscosity Lower

viscosity

better

wetting

increase

Adaptability. 3)

Co-Efficient of Thermal Expansion Zinc oxide eugenol → closer to the tooth structure ↓ Best physical adaptability to dentin ↓ Best sealer, if not subjected to dissolution and mechanical stressing

4)

Strength Increase Strength → increase adaptation

12


OPTICAL PROPERTIES Set cement is opaque. BIOLOGICAL PROPERTIES To evaluate the biological compatibility the following 4 questions should be asked: 1)

Is the material itself an irritant to the PULP DENTIN organ? And

if

so;

what

are

the

irritating

ingredients

and

characteristics? What is the material’s effect at different detective depths? 2)

Can the material create an impervious layer on cut vital dentin? And if not; how porous is the formed layer?

3)

What is the effect of the material on the permeability of the underlying dentin?

4)

Is the material thermally and electrically insulation and if it is; what should be the minimal thickness to have it clinically effective?

Biological irritation: Zinc oxide eugenol is the least irritating cement.

Mild

irritation is due to eugenol / or impurities / modifiers with in it.

Unmodified Zinc oxide comes in contact with the pulp ↓ Four Possible reactions can occur;

13


A) 1.

If the Pulp healthy & sound

2.

If the Exposure site controlled microbiologically

3.

If the Size of the exposure is reparable considering the sitar capacity 06 PULP DENTIN organ ↓ Zinc oxide eugenol contact the pulp ↓ Chronic inflammation. ↓

(i)

Inflammation remains limited, the areas will be walled of by fibrous tissues followed by matrix formation, mineralization and bridging of the exposure. Takes more than a year.

(ii)

May propagate to involve all the pulp, root canal tissues with slow, symptom less necrosis.

(iii)

May lead to complete fibrosis of pulp and root canal tissues without any bridging of exposure, leaving the Pulp Dentin organ very susceptible to any irritation with little or no defense.

(iv)

May change to acute inflammation ion through change in the microbial condition, leading to necrosis of pulp and root canal tissues.

B) Pulp undergoing acute inflammation & the microbial site of the exposure-controlled → the acute condition is suppressed ↓ 1.

Due to; pharmacological actions of Zinc oxide eugenol

14


2.

May lead to chronic inflammation (Fate is a by one of the above said reaction), Dentinal bridging is unlikely to occur in this case.

C) PULP DENTIN organ condition is same as that of (A) ↓ Additions to unmodified Zinc oxide eugenol + Sound dentin chips are implanted ↓ (i)

Fibrotic walling off and bridging of the exposure with a deposited mineralizable matrix will occur, utilizing the dentin chips as a nucleus formation.

(ii)

Deposition of reparative dentin is reasonably fast (8 weeks on Average)

D) Mechanical impingement of the unmodified Zinc oxide eugenol on the pulp tissues, either by 1. Forceful insertion, 2. Inadequate reinforcement, 3. Placement

of

thin

Zinc

oxide

eugenol

cement in contact with pulp tissues, ↓ Interface with the healing – bridging reaction. 

Any modifications in Zinc oxide eugenol, (esp., incorporating mobile and penetrating modifiers) → have irritating actions on the PULP DENTIN organ up to an effective depth of 1 mm.

15


Zinc oxide eugenol can create a completely impervious layer to elements normally present in the oral environment. If it is applied in the 0.5mm thickness and not disturbed either mechanically or by dissolution.

Zinc oxide eugenol → 

Decreases the hardness of a very minimal thickness of underlying dentin (due to chelation, it does not increase the penetrability of the underlying detain.

With its multiple pharmacological actions, it can enhance the sclerosing of underlying dentin.

Zinc oxide eugenol is an excellent thermal insulator, 0.25mm thickness is enough to impact this property.

Zinc oxide eugenol conducts minimal electric energy due to is moisture.

It is not an electric insulator at any thickness, but it has best electric insulating ability.

PH is 6.6 to 8.0

Bacteriostatic and abundant properties; they inhibit the growth of bacteria and have an anodyne or soothing effect on the pulp in deep cavities, reducing pain, when it is present.

Mc knight, (1967); Cox et al, 1978 Zinc oxide eugenol → applied to dentin → Inhibitory rather than destruction of microbial growth.

Inhibition of growth of the microorganisms may be due to the hygroscopic property of Zinc oxide eugenol.

16


Trowbridge et al, (1982) Eugenol → active ingredient, has anodyne properties loosely mixed with Zinc oxide, eugenol can inhibit the action potential in the nerve fibers of the dental pulp of the cat

Other studies on Cray fish Ozeki (1975) and on bullfrogs Kozanm, (1977) have demonstrated that 100 to 200 ppm eugenol can block nerve impulse transmission.

Tiboetts et al (1976) have shown that a Zinc oxide eugenol base under amalgam restoration is a better thermal insulator than Ca(OH)2 or zinc phosphate cements.

Das (1981) Tissue culture studies have shown that Zinc oxide eugenol is toxic to pulp cells.

Norman et al (1963) Radioactive tracer studies and scanning electron microscope analysis studies have shown that it provides a better marginal seal than the Zinc phosphate cements, although leakage increases with time.

Plant and Jones (1976) Effective insulating material and prevents galvanic action of the amalgam, thus inhibiting corrosion, another advt, is there is no heat rise during setting.

According to Scott (1979), the frequency of nerve impulse firings is increased in freshly dehydrated dentin such frequency is reduced when water is applied to the opened dentinal tubules.

Rotberg and Deshazer, (1966) Zinc oxide eugenol also has a slight demineralizing action on dentin, chelating calcium.

17


Modified Zinc oxide eugenol: o Studies by Brannstrom et al (1981) showed that, despite preventing bacterial in growth from the tooth surface, IRM may cause inflammation ion in human pulps when inserted in deep cavities with a remaining dentin thickness less the 0.5mm

FLUORIDE MODIFIED ZINC OXIDE EUGENOL Wolf et al (1993) have modified zinc oxide eugenol by adding if to a

14%

concentration

of

CaFPO 4

The

final

product

contained

approximately 2% FL2. 

In vitro and in vivo studies of the dentin of human tooth cavities in which the base was placed were made after several weeks.

Both the microhardness and the FL2 contact of the dentin covered by CaFPO4 supplemented liner were increased. In contrast, there was no effect on the microhardness in the dentin of control cavities lined solely with zinc oxide eugenol. Results of the use of zinc oxide eugenol as pulp capping and pulpotomy are a matter of controversy. 

Magnusson (1971), Nixon & Hannah (1972), Georig et al (1980) Chronic inflammation persists for extended periods of time possibly causing internal resorption

Weiss and Bjorvatn, (1970); Nixon & Hannah (1972) Bridging of the exposure site under zinc oxide eugenol is inhibited 18


Roberts et al (1973) After, pulpotomy, similar inhibition of reparative dentin formation has been reported to occur under a zinc oxide eugenol cement containing ortho - ethoxy benzoic acid.

MANIPULATION Powder – Liquid system: Powder – Liquid ratio; 4:1 to 6:1 by wt 

Bottles are shaken gently, measured quantity of powder & liquid is dispensed onto a cool glass slab or paper pad.

Bulk of the powder is incorporated into the liquid and speculated thoroughly in circular motion with a stiff bladed stainless steel spatula.

Smaller increments are then added until the mix is complete.

Two paste system: 

Equal lengths of each paste are dispensed and mixed until a uniform color is observed.

Setting time 4 – 10 minutes.

Zinc oxide eugenol cements set quickly in the mouth due to moisture and heat.

19


APPLICATION OF ZINC OXIDE EUGENOL As a Base or sub base: 1) Dry the cavity 2) Dispense a drop of eugenol and two measures of Zinc oxide on a glass slab or a paper pad. 

Incorporate half of the powder in the liquid until there is a homogenous mix.

Add smaller increments of the powder and continue mixing

after

each

addition,

accruing

the

proper

consistency for the specific indication. 3) Carry a small piece of mix with a plastic instrument (flat – bladed side) to the desired location in cavity. 4) Compact a cotton pellet and carry it with a tweezers & load it with Zinc oxide powder. 5) Adapt the Zinc oxide eugenol to the cavity walls with this cotton pellet.

Another place may be added, if desired, in the same

fashion. 6) Allow it to dry for 5 minutes. 7) Remove excess with a spoon excavator or explorer soaked in alcohol or H2O. 8) To accelerate setting, apply H2O to the surface of the base and leave it there.

20


COMPATIBILITY

OF

INTERMEDIALY

BASE

MATERIAL

WITH

RESTORATIVE MATERIALS & TECHNIQUES: 1)

Zinc Oxide Eugenol: 

The eugenol of Zinc oxide eugenol interferes with the setting reaction of any polymer & to some extent, it can even depolymerize already set polymeric materials. That is why it should not be brought into contact with resinous direct tooth – colored materials.

It can discolor other non – polymeric direct tooth colored materials as a result of its diffusion through such porous material.

It should be covered with zinc phosphate cement to minimize the amount of the eugenol seeped to the resinous restorative material.

It can interfere with the setting of poly-carboxylate cement, ASPA cements & methylcellulose carried Ca(OH), and they polymerize in contact with it.

Zinc oxide eugenol is not sufficiently rigid, tough or durable. If used as sub base or base, it should be covered with modified Zinc oxide eugenol (especially those containing EBA) or zinc phosphate cement. ↓ In case of amalgam, direct gold and cast alloy restoration due to their manipulative energies are more.

21


Indications and uses Zinc Oxide Eugenol a)

Unmodified form, Oldest and most effective intermediary base material .

b)

One of the best insulators and sealers of the P – D organ.

c)

Multiple pharmacological action; 

Antiseptic effect upon microorganism remaining in the dentin.

Sedative & anti – inflammatory action upon the P – D organ.

d)

Hygroscopic action removes excessive moisture that may add to the irritation of the Pulp Dentin organ.

e)

Sealing ability minimizes micro leakage and ingress of irritants.

f)

Insulates against thermal & galvanic shocks.

g)

Unmodified zinc oxide eugenol is the only base, which can guarantee a favorable reaction in the Pulp Dentin organ when the effective depth is less than 1 mm even if the Pulp Dentin organ has history of degeneration or is undergoing a mild one.

h)

Modified zinc oxide eugenol used as a base under amalgam & cast restoration

i)

Sub base → unmodified zinc oxide eugenol used, when Ca(OH) 2 is contraindicated for a Pulp Dentin organ with a history of degeneration.

j)

Contraindicated as a base for polymeric restorations. 22


k)

Used as a sealing agents for inter treatment dressings.

l)

Used for perforation repair.

STUDIES RELATED TO ZINC OXIDE EUGENOL 1)

Zinc oxide eugenol still remains the most effective temporary filling material when prevention of pulpal injury is of prime concern → statement by Dubner & Stanley.

2)

James & Schour → Zinc oxide eugenol may even have exerted a palliative effect on pulp. ↓ Related to the obtunding effect eugenol exerts upon sensory nerves rendering them less capable of earring the “pain message” to the brain.

3)

Das found zinc oxide eugenol cement toxic to human dental pulp cells in tissue culture more over; he found that; Zinc oxide powder alone was toxic, as were up points, which are heavily filled with Zinc oxide.

4)

In the views of meryon and Jake man, Zinc oxide released at 14 days from zinc oxide eugenol was a strong toxin in vitro against human fibroblasts, 26.88 parts per million compared to only 6.03 ppm released form Zinc phosphate cement. Absorption of the released Zinc by the remaining dentin on the cavity floor is the pulp’s saving grace.

5)

Meryon further tested zinc oxide eugenol.

23


6)

Eugenol could pass the dentin barrier. Thicker the remaining dentin less the toxic effect of eugenol. Eugenol release occurs as a result of hydrolysis of zinc eugenolate. Removal of smear layer increase the passage of eugenol to the pulp.

7)

Brannstorm & Nybori: Testing Nobetec (Aswedish modified zinc oxide eugenol cement; rosin, acrylic fibers, balsam). Believe; zinc oxide eugenol exerts Dehydrating effect that effect +5 secs of air-drying the experimental cavities could have caused the damage from desiccation apparent in their slides.

In any even; they recommended; Ca (OH) 2 liner be

placed before Zinc oxide eugenol cement is used as a base. 8)

Another study; Brannstorm & Associates:

Found IRM (zinc

oxide eugenol strengthened with polymethyl methacrylate) produced slight to moderate pulp inflammation if the dentin thickness was less than 0.5mm. They recommended the same. CAVITY 

Resin – reinforced, zinc oxide eugenol temperature. Cement used extensively in pulpless teeth.

Cavity placed against dentin covering a vital pulp it causes desiccation.

Cavity; like zinc oxide eugenol is hydroscopic, it has a 6 fold greater H2O absorption value than zinc oxide eugenol.

The pain on insertion undoubtedly arises from fluid displacement in the detain tubule. Therefore cavity should always be placed in a moist cavity. Pulpal reaction → no difference between cavit & zinc oxide

eugenol ↓ Provant & Adrian found that. 24


COMMERCIAL NAMES 1. Unmodified

2. EBA alumina Modified

-

Tempac

-

Type III

-

Cavitic

-

Type IV

-

Tempbond -

-

Opoton alumina

Type I

-

Type II

EBA 3. Polymer Modified

4. Non-eugenol

-

Fynal

-

Type II

-

IRM

-

Type III

-

Neogenol

-

Type I

-

Freegenol

-

Type I

25


Zinc oxide egunol seminar/ dental implant courses by Indian dental academy