4. Introduction Oldest of the luting cement Longest clinical
track record Serves as a standard with which newer materials canbe
compared Supplied as a powder and liquid.
5. Composition POWDER Zinc oxide - 90% Magnesium oxide 9-10 %
Bismuth trioxide, Barium oxide tracessintered at temperatures
between 1000deg Celsius and1400 deg Celsius -> cake -> fine
powderparticle size -> setting time
6. Liquid Phosphoric acid Water Aluminium Phosphate Zinc
Phosphate (some times)Water controls the ionization reaction of
acid - in turninfluence the rate of acid base reactionAcid content
of the liquid - 33% approximately.
7. SETTING REACTION When the powder is mixed with liquid ,
thephosphoric acid attacks the surface of the particles -releases
zinc ions into the liquid aluminium, whichalready forms a complex
with the phosphoric acid ,reacts with zinc - zinc alumino phosphate
gel on thesurface of the remaining portions of the particles. Water
is critical to the reaction. ZnO + H3PO4 Zn3(Po4)2 + H2O
8. Changes in composition and reaction rates mightoccur due to
degradation of the liquid or waterevaporation from the liquid
Liquid degradation effects are exhibited as clouding ofthe liquid
Loss of water from acid increases the setting time
9. Working and Setting Times Mixing time of 1.5 2 mins Setting
time 2.5 8 mins The following procedures can extend the setting
time Reducing P/L ratio Mixing in increments Prolonging the
spatulation of last increment. Cooling the glass slab
10. Physical Properties Compressive strength :104MPa Tensile
strength:5.5MPa Thermal conductivity : 3.11 mcal.cm/cm2.sec.K Low
water solubility 0.04wt% More soluble in dilute organic acids
Modulus of elasticity:13.7GPa Quiet stiff & resistant to
elastic deformationLoss/Gain water content compressive tensile
strength.
11. RetentionDoesnt involve reaction with surrounding
hardtissue/restorative materialNo chemical interactionsMechanical
bonding at interfaces
12. Biological Properties Acidity of cement is quite high
during the time ofapplication - presence of phosphoric acid2 min
after the start of mixing , Ph is 2increases rapidlyreaches about
5.5 in 24 hrs Pulpal damage can occur during first few hours. High
heat production during setting of the cement canalso cause pulpal
injury.
13. Manipulation Incorporate powder - liquid Recommended p/l
ratio 1.4gm - 0.5ml A cool mixing slab prolongs the working and
settingtimeLiquid dispensed onto the slabevaporation
14. Powder -several increments spatulated : 15 20 secs smaller
quantities - first fewincrements working - setting time. middle of
the mixing larger amountsof powder to further saturate theliquid
with newly formed zincphosphate. Finally , smaller increments are
added so that the desired ultimateconsistency of the cement is
notexceeded begins & ends with small increments
17. Introduction Zinc polyacrylate cement First - adhesive bond
to tooth structure. Supplied as Powder and liquid
18. Composition PowderZinc oxide 72% Basic ingredientMagnesium
oxide 7% Modifier , aids in sinteringOther oxides like bismuthand
aluminiumStannous fluorideIncrease strength, modifiessetting time,
impartsanticariogenic properties
19. Liquid Liqueous solution of polyacrylic acid (32-48%)Or
Copolymer of acrylic acid with other unsaturatedcarboxylic acids
(itaconic , maleic , tricarballylic acids) Molecular weight 25,000
50,000
20. Chemical reaction When acid comes in contact with powder ,
acid reactsand releases zinc, magnesium, and tin ions They bond to
the polymer chain , through the carboxylgroups These ions also
react with carboxylic groups ofadjacent poly acid chains Cross
inked salts are formed
21. Bonding to tooth structure Poly acrylic acid reacts with
calcium ions via carboxylgroups on the surface of enamel or dentin.
Bond strength greater on enamel than dentin. Enamel 3.4-13.1MPA
Dentin 2.07MPA
22. Working and Setting time Working time : 2.5 min Setting
time : 6-9 min Lowering the temperature of chemical reaction
canincrease the setting time.
23. Mechanical Properties Comprssive strength : 55-67 Mpa
Tensile strength : 2.4-4.4 Gpa Modules of elasticity is lower then
zinc phosphatecement 5.1GPa More soluble than zinc phosphate cement
0.06% More soluble in organic acids. Not as brittle as zinc
phosphate cement Excess removal is difficult.
24. Biological Consideration Pulpal response termed as mild Ph
of liquid is 1- 1.7 Freshly mixed cement 3-4 After 24 hrs 5 -6
25. Manipulation A cooled glass slab / powder 1.5 parts of
powder to 1 part of liquid by weight Liquid not dispensed , before
the start Loss of water, increases viscosity Powder is rapidly
incorporated into the liquid in largequantities Mixing time is with
in 30 60 sec ,with half to all ofpowder incorporated at once to
provide the maximumlength of working time Surface - glossy , acid
present to provide sufficientcarboxylic groups to bond.
26. Glossy AppearanceDull Appearance
27. Applications Primarily for luting permanent restorations As
bases and liners Cementation in orthodontic treatment
28. Zinc Oxide Eugenol Cement
29. Introduction These cements have been extensively used in
dentistrysince 1890 s They are least irritant of all dental cements
Have an obtundant or sedative effect Compatible with the hard and
soft tissues of themouth
30. Classification Type 1 ZOE for temporary cementation Type 2
ZOE permanent cementation Type 3 ZOE temporary filling material ,
thermalinsulation Type 4 ZOE Cavity liners
33. Setting reaction First , hydrolysis of zinc oxide to its
hydroxide Water is essential for reaction to proceed reaction is a
acid base one, Zinc hydroxide combines with eugenol to form a
chelateZnO + H2O Zn(OH)2 ZINC EUGENOLATE Forms an amorphous gel,
which later tends to crystallize. Structure : particles of
unreacted zinc oxide embedded in amatrix of zinc eugenolateZn(OH)2
+ 2HE ZnE2 + 2H2O
34. Manipulation p/l ratio 4:1 to 6:1 by wt the bulk -
incorporated into the liquid -spatulatedthoroughly in a circular
motion - a stiff bladed spatula Small increments - until the mix is
complete consistency
35. Setting time - 4-10 mins Complete setting reaction between
zinc oxide and eugenoltakes about 12 hrsFactors affecting setting
time: Particle size smaller particle size, set faster Accelerators
alcohol , glacial acetic acid , and smallamounts of water Retarders
glycol, glycerine Temperature high temperature , accelerate setting
Powder/ liquid ratio higher the ratio, faster the set
36. Physical properties Relatively week cements Compressive
strength : Ranges from 3-4mpa to 50-55mpa Tensile strength : 0.32
to 5.8mpa Modules of elasticity : 0.22 5.4 mpa Excellent thermal
conductivity Solubility of the set cement is high - disintegrate
inoral fluids - Solubility is reduced by increasing p/lratio
37. Biological properties Least irritating of all dental
cements Ph is 6.6 8 Pulp response is termed as mild They inhibit
the growth of bacteria , have an anodyneor soothing effect on pulp
, in deep cavities, hencereduces pain
38. Modified Materials Polymer reinforced ZOE introduced in an
effort to increase themechanical properties of zoe. Contains Zinc
Oxide and finely dividednatural or synthetic resin like poly
methylmethacrylate resulting in good strength,improved abrasion
resistance andincreased toughness Luting agent, Base, temporary
fillingmaterial and as a cavity liner.
39. EBA and alumina modified ZOE cement Powder : ZnO 70%
Alumina 30% Liquid: EBA 62.5% Eugenol 37.5%Properties are better
than unmodified zoeCompressive strength increased 55 mpaTensile
strength 4.1mpaModulus of elasticity 2.5 gpaSolubility and
disintegration 0.05% wt
40. Non eugenol Zinc Oxide cement Suitabe for patients
sensitive to eugenol. Eugenol acts as an inhibitor for free
redicalpolymerized materials
41. ZOE based periodontal pack It protects the wound
frommechanical trauma andstabilize the surgical site. It also
prevents post operativehemorrhage and infection;decreases
toothhypersensitivity in first fewhours after suurgery.
42. Conclusion Though cements are used in small quantities in
oralcavity, it should be used with at most care, as it is
veryimportant. There are innumerable cements presentwith different
properties, one should know all theproperties to use it in order to
give a successfulrestoration to the patient
43. References PHILLIPS , SCIENCE OF DENTAL MATERIALS 11TH
EDITION CRAIG S RESTORAIVE DENTAL MATERIALS 12TH EDITION
STURDEVANTS ART AND SCIENCE OF OPERATIVEDENTISTRY 5TH EDITION
DENTAL CLINICS OF NORTH AMERICA JULY 2007 51:3 SAUNDERS DENTAL
CLINICS OF NORTH AMERICA OCTOBER 1983 27:4 SAUNDERS
