Calcium hydroxide cements were introduced by Hermann in 1920 as an alternative to viewing exposed pulps as "doomed organs." Calcium hydroxide cements promote healing in clinical situations by creating an alkaline environment. They are formed through a reaction of calcium oxide with water to create calcium hydroxide. Typical calcium hydroxide cements are composed of calcium hydroxide, zinc oxide, zinc stearate, and ethyl toluene sulphonamide. They set through exothermic chemical reactions, have biocompatibility that can destroy bacteria and initiate reparative dentin formation, but have low strength and solubility in moisture.

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Calcium Hydroxide Cements
Professor
DR. Tahir Ali Khan

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Rebel summarized his thoughts in the
expression “the exposed pulp is a doomed
organ”
Once pulp exposed
Consider it a lost organ

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Hermann’s (1920) introduced Calcium
hydroxide formulation
The emphasis has shifted from
“Doomed Organ” concept of an
exposed pulp
To one of hope and recovery

4. Calcium hydroxide
Limestone: A natural rock
Composed of calcium carbonate
(CaCO3)
The combustion of limestone between
900ºC and 1200ºC causes the following
chemical reaction:
CaCO3 → CaO + CO2
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5. How Calcium hydroxide formed
CaO + H2O → Ca(OH)2
Strong alkali
White odorless powder
Formula: Ca(OH)2
Molecular weight: 74.08
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History
Introduction to dentistry by Hermann
Indicated to promote healing in many
clinical situations.
Initially Nygren (1838) used it for the
treatment of the `fistula dentalis',
Codman (1851) was the first to
attempt to preserve the involved
dental pulp.

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Calcium hydroxide cements
Presentation
Powder
Powder / Liquid
Paste / Paste
Single paste

9. Classification
Based on the setting time
Fast setting
Controlled setting
Slow setting
No setting
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10. Based on mechanism of setting
Self curing
Light curing
.
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11. Based on vehicle used
Aqueous vehicle
Water, saline, dental anesthetic, ringers
solution, aqueous suspension of
methylcellulose
Viscous vehicle
Glycerine, polyethylene glycol and
propylene glycol.
• Oily vehicles – Olive oil, oleic acid, linoleic
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12. Composition
1. Suspension of Calcium hydroxide
in water
2. Calcium hydroxide + water +
methyl cellulose
3. Calcium hydroxide + synthetic
resin + chloroform
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Composition of typical Calcium Hydroxide Cement
Paste 1
Calcium hydroxide 50 %
Function: Primary reactive ingredient
Zinc oxide 10 %
Function: Primary reactive ingredient
Zinc Stearate 0.5 %
Function: Accelerator
Ethyl Toluene Sulphonamide 39.5 %
Function: Oil compound acts as carrier

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Composition of typical Calcium hydroxide cement
Paste 2
Glycol Salicylate 40 %
Function: Primary reactive ingredient
Titanium dioxide
Calcium Sulphate
Calcium Tungstate
Function: Inert fillers, pigments and
radio pacifiers

15. Composition of light activated Calcium
hydroxide cement
Calcium hydroxide
Bis GMA
HEMA
Activator
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Properties
Manipulative properties
The mixed material have very low
viscosity
Setting can be relatively slow for some
products
Moisture has a dramatic effect on the rate of
setting however, material can set within few
seconds of being placed in cavity

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Setting of light cured material is
under the operator control
During setting
Temperature rises due to
Heating effect of light source
Reaction is Exothermic

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Mechanical properties
Weak cement
Compressive strength is 20 MPa

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At 7 minutes
The compressive strength : 6 MPa
The tensile strength :1.5 MPa
At 1 hour
The compressive strength :10 MPa
The tensile strength:1.5 MPa (200 psi)
At 24 hours
The compressive strength :14 to 20 MPa
The tensile strength :1.7 to 2 MPa
Thin films become resistant to 8 Mpa penetration
force in 90 seconds
At 37 deree celciuos plastic flow without fracture
occurs

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Biocompatibility
It is sufficiently biocompatible
To be placed adjacent to the pulp and capable of
destroying any remaining bacteria

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The material is bioactive
Irritation of the pulp tissues
Mediated by the activation of a cellular
growth factor (TGFβ)
Initiate Calcification and formation of
Tertiary dentin

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Solubility
Set materials have relatively high
solubility in aqueous media
Resin based Calcium hydroxide cement
are less soluble than conventional
products but still Calcium hydroxide
release remain great enough

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Application
As lining and
base agent
As a pulp
capping agent
Therapeutic root
canal sealer

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Advantages
Easy manipulation,
Rapid hardening in thin layers,
Good sealing characteristics, and
Beneficial effects on carious dentin and
exposed pulp.

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Disadvantages
Show low strength even when fully set,
Exhibit plastic deformation,
Are weakened by exposure to moisture, and
Will dissolve under acidic conditions and if
marginal leakage occurs