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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.
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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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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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
Editor's Notes
Limestone: A natural rock mainly composed of calcium carbonate (CaCO3) which forms when the calcium carbonate solution existing in mountain and sea water becomes crystallized
The combustion of limestone between 900ºC and 1200ºC causes the following chemical reaction: CaCO3 → CaO + CO2
Can be formed by the reaction of calcium oxide
The
calcium oxide (CaO) (quicklime) contacts water, the following reaction occurs
Calcium hydroxide is a white odorless powde
the initial reference to its use has been attributed to Nygren (1838) for the treatment of the `fistula dentalis',
Calcium hydroxide acts as
Antibacterial
And got alkaline pH
Calcium hydroxide is readily leached out
Generating an alkaline environment in the area surrounding the cement
This is thought to be responsible for the proven antibacterial properties of these materials
The lethal effects of calcium hydroxide on bacterial cells are probably due to protein denaturation and damage to DNA and cytoplasmic membranes.
The material is bioactive
Initiate Calcification and formation of Tertiary dentin
due to
Irritation of the pulp tissues by the cement, possibly mediated by the
Activation of a cellular growth factor (TGFβ)