Role of calcium hydroxide in endodontics

Role  of calcium hydroxide in endodontics

Calcium hydroxide

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 3^rd 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

Advantages of calcium hydroxide-

·      Initially bactericidal then bacteriostatic.

·      Promotes healing and repair.

·      High pH stimulates fibroblasts

·      Neutralizes low pH of acids

·      Stops internal resorption

·      Inexpensive and easy to use.

·      Particles may obturate open tubercles.

Disadvantages of calcium hydroxide-

·      does not exclusively stimulate dentinogenesis

·      does exclusively stimulate reparative dentin.

·      Associated with primary tooth resorption

·      May dissolve after one year with cavosurface dissolution.

·      May degrade during acid etching

·      Degrades upon tooth flexure

·      Marginal failure with amalgam condensation

·      Does not adhere to dentin or resin restoration.

Calcium hydroxide- as intracanal medicament- It is the most commonly used dressing for treatment of the vital pulp. It also plays a major role as an intervisit dressing in the disinfection of the rootcanal system.

Calcium hydroxide cannot be categorized as a conventional antiseptic,but it kill bacteria in root canal space. The value of calcium hydroxide in endodontic treatment of necrotic infected teeth is now well documented.

Calcium hydroxide is normally used as a slurry of Calcium hydroxide in a water base. At body temperature less than 0.2% ofCalcium hydroxide  is dissolved into ca++ and OH- ions.  Calcium hydroxide needs water to dissolve. Therefore it is most advantageous to use water as a vehicle for the Calcium hydroxide paste. In contact with air calcium hydroxide forms calcium carbonate.

Calcium hydroxide is a slowly working antiseptic. Direct contact experiments in vitro require a 24 hour contact period for complete killof enterococci.  Calcium hydroxide not only kills bacteria , but it also reduces the effect of the remaining cell wall material lipopolysaccharide.

Calcium hydroxide may be mixed with sterile water or saline, but this formula is also available commercially from a no. Of manufacturers in a sterile single dose packages.

 It should be mixed to a thick mixture to carry as much Calcium hydroxide particles as possible. This slurry is best applied with a lentulo spiral.

Saturated Calcium hydroxide solution mixed with a detergent is an effective antimicrobial agent suitable for irrigation.

Calcium hydroxide- as endodontic sealer-

In the root canal filling sealer plays an important role. sealer fills all the space the gutta-percha is unable to fill because of guttapercha physical’s limitations.

To be therapeutically effective calcium hydroxide must be dissociated into Ca++ and  OH-. Therefore to be effective, an endodontic sealer based on calcium hydroxide must dissolve and the solid consequently lose content. Thus one major concern is that the calcium hydroxide content dissolve, leaving obturation voids. This would ruin the function of the sealer, because it would disintegrate in the tissue.

Recently introduced several calcium hydroxide sealers are sealapex  (kerr) ,apexkit(vivadent).

Calcium hydroxide as pulp capping agent-

Calcium hydroxide is generally accepted as the material of choice for pulp capping.

Histologically there is complete dentinal bridging with heathy radicular pulp under calcium hydroxide dressings.

When calcium hydroxide is applied directly to pulp tissue there is necrosis of adjacent pulp tissue and an inflammation of contiguous tissue. Dentinal bridge formation occurs at the junction of necrotic tissue and vital inflamed tissue. Beneath the region of necrosis, cells of underlying pulp tissue differentiate into odontoblasts and elaborate dentin matrix.

Three main calcium hydroxide products are-

Pulpadent ,Dycal,Hydrex (MPC).

Pulpadent paste is considered to be most capable of stimulating early bridge formation.

Hydrex has been considered that fast capable of forming a bridge.

Commercially available compounds of calcium hydroxide in a modified form are known to be less alkanine and thus less caustic on the pulp.

The action of calcium hydroxide to form a dentin bridge appears to be a result of the low grade irritation in the underlying pulp tissue after application.

Calcium hydroxide in apexification-

In apexification technique canal is cleaned and disinfected. when tooth is free of signs and symptoms of infection, the canal is dried and filled with stiff mix of calcium hydroxide and CMCP.

Commercial paste of calcium hydroxide(egCalasept, Pulpdent, Hypo-cal, Calyxl) may be used to fill the canals.

Histologically the formation of osteodentin after placement of calcium hydroxide paste immediately on conclusion of a vital pulpectomy has been reported. There appears to be a differentiation  of adjacent connective tissue cells ; there is also deposition of calcified tissue adjacent to the filling material. the calcified material is continuous with lateral root surfaces. the closure of apex may be partial or complete but consistently has minute communications with the periapical tissue.

Calcium hydroxide in pulpotomy –

It is the most recommended pulpotomy medicament for pulpally involved vital young permanent tooth with incomplete apices.

It is acceptable because it promoted reparative dentin bridge formation and thus pulp vitality is maintained.

Histologically pulp tissue adjacent to calcium hydroxide was first necrotised by the high pH of calcium hydroxide. This necrosis was accompanied by the acute inflammatory changes in the underlying tissue. After 4 weeks a new odontoblastic layer and eventually a bridge of dentin developed.

Three  histologic zones under calcium hydroxide in 4-9 days:

1.  Coagulation necrosis

2.Deep staining areas with varied osteodentin

3.Relatively normal pulp tissue, slightly hyperemic, underlying an odontoblastic layer.

Internal resorption may result from overstimulation of the primary pulp by the highly alkaline calcium hydroxide. This alkaline induced overstimulation could cause metaplasia within the pulp tissue, leading to formation of odontoclasts. Also undetected microleakage could allow large numbers of bacteria to overwhelm the pulp and nullify the beneficial effects of calcium hydroxide.

Calcium hydroxide incorporated in a methylcellulose base such as pulpdent, showed earlier and more consistent bridging.

At present calcium hydroxide pulpotomy technique cannot be generally recommended for primary teeth.

But it is the recommended agent for carious and traumatic exposures in young permanent teeth, particularly with incomplete closure.

Calcium hydroxide in weeping canals-

Sometimes a tooth undergoing root canal treatment shows constant clear or reddish exudate associated with periapical radiolucency. Tooth can be asymptomatic or tender on percussion. When opened in next appointment ,exudates  stops but it again reappear in next appointment. This is known as “weeping canal”.

In these cases tooth with exudates is not ready for filling,since culture reports  normally show negative bacterial growth so,antibiotics are of no help. For such teeth dry the canals with sterile absorbant paper points  and place calcium hydroxide in canal. It happens because pH of periapical tissues is acidic in weeping stage which gets converted into basic pH by calcium hydroxide.