Antimicrobial mechanism of CALCIUM HYDROXIDE

CALCIUM HYDROXIDE

Antimicrobial activity of calcium hydroxide is related
to the release of hydroxyl ions in an aqueous
environment.

Hydroxyl ions are highly oxidant free
radicals that show extreme reactivity, reacting with
several biomolecules.

Their lethal effects on bacterial cells are probably due to the
following mechanisms:

1.Damage to the bacterial cytoplasmic membrane

2.Protein denaturation

3.Damage to the DNA


Damage to the bacterial cytoplasmic membrane

Hydroxyl ions induce lipid peroxidation, resulting in
the destruction of phospholipids.

Hydroxyl ions remove hydrogen atoms from unsaturated fatty acids,
generating a free lipidic radical.

This free lipidic radical reacts with oxygen, resulting in the formation of a
lipidic peroxide radical, which removes another hydrogen atom from a second fatty acid, generating another lipidic peroxide.

Thus, peroxides themselves act as free radicals, initiating an autocatalytic chain
reaction, and resulting in further loss of unsaturated
fatty acids and extensive membrane damage.
(Halliwell 1987, Cotran et al. 1999)

Protein denaturation


Cellular metabolism is highly dependent on enzymatic
activities.

The alkalinization provided by calcium
hydroxide induces the breakdown of ionic bonds that
maintain the tertiary structure of proteins


the enzyme maintains its covalent
structure but the polypeptide chain is randomly
unravelled in variable and irregular spacial conformation.

These changes frequently result in the loss of
biological activity of the enzyme and disruption of the
cellular metabolism.
(Voet & Voet 1995).


Damage to the DNA

Hydroxyl ions react with the bacterial DNA and induce
the splitting of the strands.

DNA replication is
inhibited and the cellular activity is disarranged. Free
radicals may also induce lethal mutations.

(Imlay & Linn 1988)

ANOTHER MECHANISM

It has been suggested that the ability of calcium
hydroxide to absorb carbon dioxide may contribute to
its antibacterial activity
(Kontakiotis et al. 1995)

calcium hydroxide impedes the carbon dioxide supply
to bacteria.

Reference
International Endodontic Journal, 32, 361-369, 1999

CHEMICOMECHANICAL CARIES REMOVAL (CARISOLV)

CARIDEX

The chemo-mechanical system for caries removal was published in 1975 by HABIB et al.

It is marketed under the trade name of Caridex.

Chemo-mechanical caries removal uses sodium hypochlorite (NaOCl), a non-specific proteolytic
agent (monoaminobutyric acid) removing organic components at room temperature


CARISOLV

Carisolv consists of a red gel and transperant fluid.

composition

Red gel
glutamic acid,
leucin,
lysine,
sodium chloride,
erythrosine,
water and sodium hydroxide

Transparent fluid
0.5% sodium hypochlorite


The chemical action of Carisolv is similar to that of Caridex in softening the carious dentin but leaving the healthy dentin unaffected

In caridex it was shown that, NaOCl was dissolving not only necrotic tissue but also sound dentin.

INSTRUMENTS
Special instruments designed to scrape in two or in several directions, which reduce the friction during caries excavation

MECHANISM OF ACTION

While mixing amino acids react with sodium hypochloride and forms chloromines.

chloromines seems to involve the chlorination of partially degraded collagen and the conversion of hydroxyproline to pyrrole-2-carboxylic acid, which initiates disruption of altered collagen fibres in carious dentin .