Calcium hydroxide cements

Histroty, classification, composition, properties, uses, advantages and disadvantages

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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
(CaCO
3)
The combustion of limestone between
900ºC and 1200ºC causes the following
chemical reaction:
CaCO
3
→ CaO+ CO
2
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5. How Calcium hydroxide formed
CaO+ H
2O → 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 Stearate0.5 %
Function: Accelerator
Ethyl Toluene Sulphonamide39.5 %
Function: Oil compound acts as carrier

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Composition of typical Calcium hydroxide cement
Paste 2
Glycol Salicylate40 %
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
BisGMA
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