MECHANISM OF CALCIUM HYDROIDE IN ROOT CANAL

CALCIUM HYDROXIDE

Since its introduction in 1920 (Hermann 1920), calcium hydroxide has been widely used in
endodontics.

It is a strong alkaline substance, which has a pH of approximately 12.5. In an aqueous
solution, calcium hydroxide dissociates into calcium and hydroxyl ions.

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.

Damage to the bacterial cytoplasmic membrane

Hydroxyl ions induce lipid peroxidation, resulting in the destruction of phospholipids, structural components of the cellular membrane.

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.

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

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.

Genes are then lost , Consequently, DNA replication is inhibited and the cellular activity is disarranged.

Free radicals may also induce lethal mutations.
(Imlay & Linn 1988).
...
It has been suggested that the ability of calcium hydroxide to absorb carbon dioxide may contribute to
its antibacterial activity (Kontakiotis et al. 1995).