Calcium hydroxide was originally introduced to
the field of endodontics by Hermannin 1920 as
a pulp-capping agent, but its uses today are
widespread in endodontic therapy.
It is basic compound with an appropriate pH of 11. As such it is mildly irritating to vital pulp tissue.
It also has bacteriostatic properties which means it keeps bacteria from actively spreading. both of these qualities make it a good linig material for restoration in close proximity to pulp.
Although calcium hydroxide does not bond to dentin it does have antibacterial property. It continues to have a high pH after setting because material dissolve readily in aq. Solution, liberting hydroxyl ions.
This high pH provides a stimulus for tooth to repair itself in absence of bacterial infection.
It is supplied in several forms. Sold as a liquid containing calcium hydroxide suspended in a solvent also it is supplied as a paste in which calcium hydroxide is suspended in metylcellulose. In these first two forms material is used like a varnish. In its 3rd common form calcium hydroxide is supplied as a 2-paste system in tubes marketed catalyst and base.
It is mixed with several other ingredients such as zinc oxide and calcium phosphate. A catalyst is present to cause calcium hydroxide to react and form a hard, amorphous compound with in matter of min under oral condition. Finally a fourth calcium hydroxide paste formulation contains a polymer resin that can be hardened by illumination from a handheld blue light source.
Properties of calcium hydroxide-
COMPONENTS-
· Compound 1 and 2= paste with calcium hydroxide ,lc resin and polyphenolics.
· p/l or p/p ratio= 1 compound
· setting reaction= acid base reaction
STRUCTURE-
· arrangement= amorphous matrix, crystalline fillers.
· Bonding= covalent; ionic
· Composition= multiphase
· Defects=pores, cracks
PHYSICAL PROPERTIES-
· LCTE= low
· Thermal conductivity= insulator
· Electrical conductivity= insulator
CHEMICAL PROPERTIES
· Solubility- 0.3-0.5
MECHANICAL PROPERTIES
· Elastic mod=588
· Compressive strength >24 hr=138
BIOLOGIC PROPERTIES
· Biocompatible
.