Presented byNisar ahmed

Contents• Introduction• History• Composition• Setting mechanism• Classification• Physical properties• Chemical characteristics• Biochemical actions• pH variation of calcium hydroxide on pulp tissue healing• Dental formulations of calcium hydroxide• Types of vehicles and their clinical importance• Applications in dentistry• Advantages• Disadvantages

INTRODUCTION

• During the last 200 years there have been many changes in the rationale governing the treatment of the exposed dental pulp as it was long ago observed that an exposed pulp healed with great difficulty, if at all.

• The earliest account of pulp therapy was way back in 1756, when Phillip Pfaff packed a piece of gold over an exposed vital pulp to promote healing.

• Rebel summarized - “the exposed pulp is a doomed organ”.

• Hermann’s (1920) introduction of a material is so eminent, which marked a new era in pulp therapy, when he demonstrated that a Calcium hydroxide formulation called Calxyl induced dentinal bridging of the exposed pulpal surface.

• Since then the emphasis has shifted from the “doomed organ” concept of an exposed pulp to one of hope and recovery.

• Calcium hydroxide made a major break through in dentistry ever since it

had been introduced.

 

• In its pure form, the substance has a high pH, and its dental use relates

chiefly to its ability to stimulate mineralization, and also to its

antibacterial properties

 

History• 1920 - Herman introduced Calcium hydroxide in to the field of

dentistry. (pH of approximately 12.5)

• Nygren (1938) -The initial reference to its use for the treatment of the "fistula dentalis".

• According to Cvek (1989) calcium hydroxide became more widely

known in 1930's through the pioneering work of Hermann and the introduction of this material in the United States In 1939 by Zander

• Year 1934-1941 - The first literature regarding the successful healing

• 1940 – Rhoner – as root canal filling material

Year 1959 – Granath- apical closure

Year 1960 - Matsumiya and Kitumura – antimicrobial action

Year 1966 - Frank – popularised for apical closure.

Year 1975 - Maisto classified it as an alkaline paste because

of its high pH.

Year 1976 - Cvek - induction of hard tissue in the apical portions of the

root canal, of immature teeth with infected pulp necrosis.

Year 1983 - Garcia considered calcium hydroxide as the best

medicament to induce hard tissue deposition and promote healing of

vital Pulpal and periapical tissues.

Year 1985 - Bystrom and Sundquist promoted calcium hydroxide as an

antibacterial agent and showed that 97% of the cases showed great

success with calcium hydroxide.

Year 1985 - Bystrom - Enterococcus faecalis - tolerated calcium

hydroxide.

1988 - Hasselgren et al.- ability to dissolve necrotic material

1995 - Kontakiotis et al. It has been suggested that the ability of calcium

hydroxide to absorb carbon dioxide may contribute to

its antibacterial activity

Year 2000 - Haapsalo suggested the probable reasons for the decreased

action of calcium hydroxide as dentin debris and tissue remnants.

• Year 2002 - Peters questioned the effectiveness of calcium hydroxide and suggested that calcium hydroxide may not be as effective as it was once believed.

• Watts and Peterson (1987) Established that bacteria may be present in contact with calcium Hydroxide.

• This could lower the pH of the material by converting to calcium carbonate and might explain why early Dycal preparations seemed to disappear from beneath permanent restorations (Akester 1979 Bames and Kidd 1979).

COMPOSITION OF CALCIUM HYDROXIDE

• Calcium hydroxide is in the powder form and can be carried to the tooth in a variety of ways depending upon the need and vehicles or may be applied in the pure powder form with any carrier.

• The most common way of introducing calcium hydroxide into the cavity preparation is through calcium hydroxide cements. They are supplied in a two paste system.

The acidic paste : • Alkyl salicylates – glycol salicylate 40%- reacts with Ca(OH)2 and ZnO• Inter fillers – titanium dioxide 12-14%• Radiopacifier – barium sulphate 32-35% • Calcium tungstate or calcium sulphate 14-15% - pigments

The basic paste

• Calcium hydroxide 50-60% - reactive ingredient• Zinc oxide 10% - reactive ingredient• Zinc stearate 0.5% - accelerator• Ethylene toulene • Plasticizer (sulfonamide or paraffin oil)

The single paste or the light cured calcium hydroxide composes of : • Urethane dimethacrylate • Hydroxymethacrylate (HEMA) • Calcium hydroxide • Barium sulphate• all these ingredients are dispensed in ethylene toulene sulfonamide of

39.5%

• DYCAL:

BASE PASTE CATALYST PASTE

1.Disalicylate ester of 1,3 butylene glycol

2.Calcium phosphate

3.Calcium tungsate

4.Zinc oxide

5.Iron oxide

1.Calcium hydroxide

2.Ethyl toulenesulfonamide

3.Zinc sterate

4.Titanium dioxide

5.Zinc oxide

6.Iron oxide

Classification

I. According to, whether they are setting or non-settingA. Setting material:1. Strong effect: Reocap Procal

2. Medium effect: Life Renew Reolite

3. No effect:• Hydrex

E. feacalis.Prevotella alactolyticusP. propionicumFusibacterium alocisD. pnumosintis

• B Non-setting:• Analar calcium hydroxide• Pulp dent methyl cellulose• hypocal methyl cellulose• Reogan methyl cellulose

• A. SETTING MATERIAL:-• THERAPEUTIC PROPERTY:

Dependent on its ph and ph is inturn dependent on the free ca+ and hydroxyl ions.

The set cement contains a matrix of calcium alkyl salicylate chelate, and excess unreacted calcium hydroxide.

The fragility of set cement suggests that the chelates are held, together by weak, secondary attractions rather than a stronger polymeric structure (Prosser et al, 1979).

CHELATES?

Setting mechanism of Ca(OH)2 of setting material

There are two basic setting mechanisms

The two paste system - It is based on the reaction between calcium and zinc ions and a salicylate and is a accelerated by presence of H2O.

• Acid-base reaction. The phenolic group in the alkyl salicylate ester acts as an acid

The single paste system - This utilizes the polymerization of a dimethacrylate by means of light.

Ex: Prisma V.L.C Dycal

• A potential disadvantage of the dimethacrylate systems, when used as a base beneath composite restorations, is their adherance to the composite material and subsequent withdraw from the base of the cavity during polymerization.

B. Non setting material:• the mixing of this material with water or saline leads to formation of slurry.

•To overcome this disadvantage, calcium hydroxide is carried by methylcellulose or

any other biologically compatible and degradable polymeric material.

•calcium hydroxide does not actually take part in the chemical reaction.

•Here the methylcellulose monomers will polymerize creating a porous meshwork.

There is a chemical coherence of the ingredients creating bonding between the

polymer macromolecules.

•Methylcellulose?

• The free calcium hydroxide is carried to the pulp-dentin organ, where it is

available to engage in therapeutic action.

II. Vehicles used for calcium hydroxide According to Fava [1991] Holland [1994] the vehicles used are divided into • Aqueous ; water, saline, sterile distilled water etc• Viscous : glycerine, polyethyl glycol etc• Oily : olive oil, camphorated parachlorophenol

III. Depending on number of Components• Single paste systemEx: hypocal, etc

• two paste system: Ex: alkaliner, dycalAcid paste and base paste

• iv.calcium hydroxide-releasing gutta-percha point (CH points):

• alkalizing potential significantly lower compared with an aqueous suspensive of calcium hydroxide,

• could not be maintained for long than 3 days (7-9).

• Calcium Hydroxide Plus Points (Roeko, Langenau, Germany),

• The manufacturer states that they have enhanced mobility of hydroxyl ions through dentin.

• It has been shown that hydroxyl ions derived from calcium hydroxide diffuse

through root dentin and are measurable pH gradient across it . However the diffusion dynamics of hydroxyl ions through root dentin from this product Shows that CH+ points maintained an inner dentin environment above pH 9.5 for an average of 57 h,(aqueous calcium hydroxide paste 203 h).

•

• An interesting observation was made where outer dentine was concerned; CH+ points maintained an outer dentin pH above 9.5 for 46.3 ± 6 h, whereas aqueous calcium hydroxide paste never reached this level.

•This illustrates the increased mobility of the hydroxyl ions released by the CH+ points compared with aqueous calcium hydroxide paste

v. root canal sealers:Ex: • Sealapex.

• Calcibiotic root canal sealers (CRCS)

PROPERTIES OF CALCIUM HYDROXIDE

Setting time and the factors affecting it

• The setting time is approximately 2.5 to 5.5 minutes.

• The setting time for polymer carried calcium hydroxide can be increased by increasing the ratio of the catalyst to base paste.

• The setting time of calcium hydroxide alkyl salicylates cement can be accelerated by moisture and heat.

• Conversely, the setting time will be retarded by dryness and cold.

Dimensional stability and factors affecting it

Setting shrinkage

• The maximum setting shrinkage - 5% by volume - is of no clinical significance.

Solubility and disintegration

• Clinical tests reveal that calcium hydroxide in any form is the most soluble material.

• The greater the percentage of the original (or dispersed) particles bound to the matrix, lesser will be its solubility, that is increasing the powder: liquid ratio to the full bonding capacity of the liquid will definitely decrease the solubility and disintegration.

Flow (viscosity) :

• Although high flow is required during the insertion of the material low flow is necessary for the mechanical well being.

• Polymer carried and cement type calcium hydroxide have the highest flow and its flow is decreased by increasing the degree of polymerization of the carrying polymer or the percentage of calcium alkyl salicylate in the mix.

• Calcium hydroxide is also thermoplastic in nature and hence the flow increases with an increase in the temperature.

• Thermoplastic? Substance which becomes plastic on heating and harden on cooling

Strength :

• Polymer Carried calcium hydroxide and those with the continuous phase in the form of calcium alkyl salicylate chelate can have compressive strength up to 800 psi, while non carried calcium hydroxide has virtually no strength.

• The tensile strength is very low of about 1.0 MPa. Calcium hydroxide cements are viscoelastic. That is why they react more favorably.

• Psi: pounds per square inch• 1psi=0.00689 mpa

Adaptability :

Film thickness : • The lower the film thickness of the material, the better is its

wetting ability and better is its adaptability.

• Calcium hydroxide has the highest possible film thickness,

ranging from 70-90 microns.

• Calcium hydroxide has none of the adaptability enhancing properties and thus lowest adaptability to the tooth surfaces.

 

Biological compatibility of calcium hydroxide with the pulp-dentin organ

• Calcium hydroxide is an irritant to the pulp-dentin organ, if it comes in direct contact with it.

• Provided the pulp and the periapical tissues are healthy and devoid of any degeneration, the following Pulpal reaction to calcium hydroxide can occur:

1. Whenever there is an effective depth of 100 microns or more, a

healthy reparative dentin can form.

2. With less than 100 microns an unhealthy reparative dentin can be expected.

3. When calcium hydroxide comes in contact with the pulp or root canals the area of tissues in direct contact would undergo chemical necrosis.

• Also calcium hydroxide can stimulate the formation barrier when in direct contact thus decreasing the permeability of the dentin.

• If used in sufficiently thick layers’ they provide some thermal insulation. However, a thickness greater than 0.5mm in not recommended. Thermal protection should be provided with a separate base.

• Calcium hydroxide in any form is not an electrical insulator at any thickness.

Toxicity of calcium hydroxide

• Some calcium hydroxide preparations like Dycal, Life and Sealapex

have been associated with toxicity in the form of

• cytotoxicity,

• genotoxicity,

• neurotoxicity,

• phototoxicity,

• symptoms observed in Neuro Cutaneous Syndrome (NCS).

Neurocutaneous Syndrome (NCS)- A toxicity disorder from dental sealants

characterized by

•neurological sensations, pain,•depleted energy •memory loss as well as •itchy cutaneous lesions which may invite various opportunistic infections.

Ethyl toluene, sulfonamide is considered the primary cause of the NCS A

L

L

E

R

G

Y

Compatibility of calcium hydroxide with restorative materials and techniques :

• Calcium hydroxide has no effect on the setting reaction or the properties of any permanent restorative material. It does not discolor any permanent restorative material.

• However, in translucent tooth-colored materials, especially with thin cross-sections, calcium hydroxide will show through as a chalky patch.

• Calcium hydroxide base can be used under the amalgam and direct tooth-colored materials but when used under the direct filling gold and cast restorations calcium hydroxide should be covered with zinc phosphate or polycarboxylate cement.

• Calcium hydroxide in methylcellulose, reacts with the zinc oxide eugenol and hence not used together.

The technique of manipulation of calcium hydroxide Two paste • Equal parts of base and catalyst paste are squeezed out and incorporated

in each other with a stiff spatula on a paper pad until a homogenous mix is obtained.

Calcium hydroxide in powder form • Calcium hydroxide powder is carried between the beaks of a tweezers

and delivered to the indicated area by releasing the tweezers beaks.  Calcium hydroxide in endodontics • There are various ways with which calcium hydroxide can be placed in the

root canals. Using a messing gun, vertical compaction, an injectable formulation of calcium hydroxide, a lentulo spiral, a hand file and paper points.

• The use of a lentulo spiral was thought to be the most effective form of delivering calcium hydroxide into the root canals.

Chemical characteristics

• Synonyms- slaked lime, hydrated lime, pickling lime

• It is a chemical compound with the chemical formula Ca(OH)2.

• It is a colourless crystal or white odourless powder

H H

OO

Ca

• Molecular weight - 74.08

• It has low solubility in water (about 1.2 g L'1 at 25° C), which decreases

as the temperature rises

This low solubility is, in turn, a good clinical characteristic because a

long period is necessary before it becomes soluble in tissue fluids when

in direct contact with vital tissues.

• High ph - 12.5-12.8

• Is insoluble in alcohol. 

• The material is chemically classified as a strong base

• Limestone is a natural rock mainly composed of calcium carbonate (CaCO3) which forms when the calcium carbonate solution existing in mountain and sea water becomes crystallized

Calcination of calcium carbonate 900 and 1200' C

CaCO3 CaO + C02

(“lime” or “quicklime" , has a strong corrosive ability)

Hydration of calcium oxide calcium oxide is mixed, or “slaked” with water

CaO + H20 → Ca(OH)2

• It can also be precipitated by mixing an aqueous solution of calcium chloride and an aqueous solution of sodium hydroxide.

• A suspension of fine calcium hydroxide particles in water is called milk of lime.

• The solution is called lime water and is a medium strength base that reacts violently with acids and attacks many metals in presence of water.

• It turns milky if carbon dioxide is passed through, due to precipitation of calcium carbonate.

• A chemical analysis of OH' ionic liberation from calcium hydroxide allows the percentages of Ca+2 and OH- ions that are released to be determined (Estrela 1994):

Ca(OH) 2 -> Ca2+ + 2OH-

1n Ca+2 = 40.08

1n OH- = 17.0

2n OH- = 34

1" Ca(OH)2 = 40.08 + 34 = 74.08 (molecular weight) 

% of OH- and Ca2+

2OH-= 45.89%

Ca2+ = 54.11%

 

• The main actions of calcium hydroxide come from the ionic dissociation of Ca2+ and OH- ions, and the action of these ions on vital tissue and bacteria generates the induction of hard tissue deposition and the antibacterial effect

• However, when Ca2+ ions come into contact with carbon dioxide (Co2) or carbonate ions (CO3) in tissue, calcium carbonate is formed which alters the mineralization process by the overall consumption of the Ca2+ ions

• Furthermore calcium carbonate has neither biological nor antibacterial properties

MECHANISM OF ACTION:

1.

2.

3.

MECHANISM OF ANTIMICROBIAL ACTIVITY

• Most of the endodontic pathogens are unable to survive in the highly alkaline environment provided by calcium hydroxide.

• Since the pH of calcium hydroxide is about 12.5, several bacterial

species commonly found in infected root canals are eliminated after a short period when in direct contact with this substance

 • 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. This reactivity is high and indiscriminate, so this free radical rarely diffuses away from sites of generation.

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

1) Damage to the Bacterial cytoplasmic membrane

The bacterial cytoplasmic membrane posses important functions to the survival of the cell, such as

Selective permeability and transport of solutes

Electron transport and oxidative phosphorylation in aerobic species;

Excretion of hydrolytic exoenzymes

Bearing enzymes and carrier molecules that function in the biosynthesis of

DNA, cell wall polymers, and membrane lipids; and

Bearing the receptors and other proteins of the chemotactic and

other sensory transduction systems  

Hydroxyl ions Lipid peroxidation Destruction of phospholipids

(structural components of

cellular membrane)Remove H+ from unsaturated fatty acids, generating a free lipid radical

React with oxygen

Lipid peroxide radical

Removes another hydrogen atom from 2nd 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

2.Protein denaturation

Alkalinization by Ca(OH)2

Break down of ionic bonds of protein

Polypeptide chain unravelled to irregular spacial conformation

Loss of biological activity of enzyme and disruption of cellular metabolism.

•Cellular metabolism is highly dependent on enzymatic activities•Enzymes have optimum activity and stability in a narrow range of pH

3.Damage to DNA3.Damage to the DNA

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

Genes are then lost

DNA replication is inhibited and cellular activity disarranged.

cementum is permeable to water, ions and small molecules. Hence carbon dioxide supply to remaining bacterium in the root canal system may be maintained from outside.

In addition, bacteria located in ramifications have direct access to CO2 from the periradicular tissues

Destruction of bacteria when calcium hydroxide is used as pulp dressing :

• Some of the healing properties of calcium hydroxide may be attributed to its antibacterial effects.

• Under normal conditions healing is due to the antibacterial activity of calcium hydroxide, rather than any effect it may exert on mineralization.

• The bacterial properties are thought to be related to pH, and are directly proportional to the ability of calcium hydroxide to diffuse from the set material

• There would appear to be no clinical indications for the use of calcium hydroxide in large old exposures with deep penetration of bacteria and chronic inflammation of the pulp, unless a radical pulpotomy has been performed first.

• In this situation, calcium hydroxide does not have the same healing potential that it exhibits when used as a root canal dressing to treat a chronically inflamed periapical tissue.

• This is possibly because of the ready availability of healthy blood vessels in the periapical tissues, compared to the paucity in dying tissues in the enclosed environment of the pulp.

• It has been found that calcium hydroxide kills only the bacteria on the surface of the pulp and not those that have penetrated the necrotic tissue.

• Thus the material has no beneficial effect on the healing of the inflamed pulp, and its use would appear to be indicated for healthy or superficially contaminated pulp where bacteria have not penetrated deep.

 

Hydroxyl ions Lipid peroxidation Destruction of phospholipids

(structural components of

cellular membrane)Remove H+ from unsaturated fatty acids, generating a free lipid radical

React with oxygen

Lipid peroxide radical

Removes another hydrogen atom from 2nd 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

2.Protein denaturation

Alkalinization by Ca(OH)2

Break down of ionic bonds of protein

Polypeptide chain unravelled to irregular spacial conformation

Loss of biological activity of enzyme and disruption of cellular metabolism.

•Cellular metabolism is highly dependent on enzymatic activities•Enzymes have optimum activity and stability in a narrow range of pH

3.Damage to DNA3.Damage to the DNA

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

Genes are then lost

DNA replication is inhibited and cellular activity disarranged.

Destruction of bacteria when calcium hydroxide is used as a Root canal medicament :

• There is some uncertainty as to the efficacy of calcium hydroxide compared with the other medicaments when used as an intra canal dressing.

• When used as a root canal medicament any material must be judged entirely on its antibacterial potential acting with out support from the tissue defense mechanisms.

• Thus in contrast to its mode of action in mineralization, calcium hydroxide has a non-specific bactericidal action within the confines of the root canal

• Alkalis in general have a pronounced destructive effect on cell membranes and protein structures.

• Although most microorganisms are destroyed at pH 9.5 a few survive at pH 11 or higher.

• The main issue is not “how bacteria are killed” but how the vital tissues can be protected from the toxicity of calcium hydroxide.

• This is brought about by the separation of the material from the vital tissues by a zone of necrosis.

• For calcium hydroxide to act effectively as an intra canal dressing, the hydroxyl ions must diffuse through dentin and pulpal tissue remnants at sufficient concentrations.

• The pH values were decreased in the more distant areas from the root

canal. In the root canal, the pH was greater 12.2;• circumjacent dentine, in direct contact with calcium hydroxide, showed a

pH varying from 8 to ll ; and • in the most peripheral dentine, the pH ranged from 7.4 to 9.6

• It has been reported that dentin has buffering ability because of the presence of proton donors such as H2PO4,H2CO3 and HCO3, in the hydrated layer of hydroxyapatite, which furnish additional protons to keep the pH unchanged. Therefore, in order to have antibacterial effects with in the dentinal tubules, the ionic diffusion of calcium hydroxide should exceed the dentin buffer action, reaching pH levels sufficient to destroy bacteria.

• After short term use of calcium hydroxide, microorganisms are probably exposed to the lethal levels of hydroxyl ions only at the tubule orifice.

• Another factor can also help to explain the inefficacy of calcium hydroxide in disinfecting dentinal tubules is that the arrangement of the bacterial cells colonizing the root canal walls can reduce the antibacterial effects of calcium hydroxide, since the cells located at the periphery of the colonies can protect those located more inside the tubules.

• Bacteria colonizing necrotic tissue in the ramifications, isthmus and the irregularities are also, probably protected from the action of calcium hydroxide due to the neutralization of the pH.

• Therefore, as a short term dressing which appears to eliminate mainly bacterial cells in direct contact with this substance, such as bacteria located in the main root canal or in the circumpulpal dentin.

• The activity of a medicament to dissolve and diffuse in the root canal system would seem essential for its successful action.

• A saturated aqueous suspension of calcium hydroxide possesses a high pH, which has a great cytotoxic potential.

• Nevertheless, this substance owes its biocompatibility to its low water solubility and diffusibility.

• Because of these properties, cytotoxicity is limited to the tissues which are in direct contact with calcium hydroxide.

• On the other hand the low solubility and diffusibility of calcium hydroxide may make it difficult to reach a rapid and significant increase in the pH to eliminate the bacteria located in the dentinal tubules and enclosed in the anatomic variations.

• Likewise the tissue buffering ability controls the pH changes

• Prolonged exposure may allow for saturation of dentin and tissue remnants.

• Theoretically, long term use of calcium hydroxide may be necessary to obtain a bacteria free root canal system.

• However, in most instances, the routine use of an intra canal medicament for a long period does not seem to be an acceptable practice in endodontics.

Bacteria may survive after intra canal medication for several reasons.

• May be intrinsically resistant to the medicament.

• In an anatomical variation, inaccessible to the medicament.

• the medicament may be neutralized by the tissue components and by the bacterial cells or products, losing its antibacterial effects.

• the medicaments may remain in the root canals for insufficient time to reach and kill the bacterial cells.

• bacteria may alter their pattern of gene expression after changes in the environmental conditions.

• It is postulated that a virulence factor of E.faecalis in failed endodontically treated teeth may be related to the ability of E.faecalis cells to maintain the capability to invade dentinal tubules and adhere to collagen in the presence of human serum.

• Evans et al. studied the mechanisms involved in the resistance of E.faecalis to calcium hydroxide and found that it was resistant to calcium hydroxide at a pH of 11.1 but not at pH 11.5.

• Addition of a proton pump inhibitor resulted in dramatic reduction of cell viability of E.faecalis to calcium hydroxide

• Good clinical results have been attributed to the use of calcium hydroxide as an intra canal medicament. Nonetheless, the antibacterial activity of calcium hydroxide is still controversial.

Proton-pump inhibitors (PPIs) are a group of drugs whose main action is a pronounced and long-lasting reduction of gastric acid production. They are the most potent inhibitors of acid secretion available

Calcium hydroxide as a barrier

• In preparation of the root canal, intra canal medicament have been advocated for other reasons also, like, they should act as a physico-chemical barrier, precluding proliferation of residual microorganisms and preventing the re-infection of the root canals by bacteria from the oral cavity.

• Intra canal medicaments may prevent the penetration of bacteria from saliva in the root canal basically in two ways.

First the medicament possessing antibacterial properties may act as a chemical barrier against leakage by killing bacteria, thereby preventing their ingress into the root canal.

Secondly, medicaments that fill the entire length of the canal act as a physical barrier against penetration thereby preventing recontamination.

• The filling ability of calcium hydroxide pastes is probably more important in retarding root canal recontamination than the chemical effect because

• calcium hydroxide has low water solubility,

• slowly dissolves in saliva, remaining in the canal for a long period, delaying the bacterial progression towards the apical foramen.

• Despite the vehicle used, calcium hydroxide seems to act as an effective physical barrier.

• Medicaments that act as a physical barrier can kill remaining microorganisms by withholding substrate for the growth and limiting space for multiplication. (one of the factors possible for the antibacterial actions of calcium hydroxide.)

Siqueira et al. (1998):

Evaluated the in vitro ability of some medicaments in preventing thorough recontamination of coronally unsealed root canals by bacteria from saliva.

Material used Recontamination periodCMCP 6.9 days

calcium hydroxide/saline solution

14.7

calcium hydroxide/ CMCP/glycerine

16.5

INITIATION OF MINERALIZATION

• It seems that calcium hydroxide has the unique potential to induce mineralization, even in tissues which have not been programmed to mineralize.

• Calcium ions and the alkaline pH have been proposed to act separately or synergistically in promoting calcification.

• It was once believed that the calcium ions present in the applied

calcium hydroxide does not become incorporated in the mineralized repair tissue, which derives its mineral content solely from the dental pulp, presumably via the blood supply. However the present day belief is that the calcium ions from the medicament do enter into the bridge formation.

Ca (OH)2

ca2+ OH-

Reduced capillary permeability Neutralizes acids produced by osteoclasts

Reduced serum flow Optimum pH for pyrophosphatase

Reduced levels of increased levels of calcium inhibitory pyrophosphatase dependent pyrophosphatase Uncontrolled mineralization

• This could possibly explain the high incidence of mineralized canals observed following pulpotomy and direct pulp treatment.

• Uncontrolled mineralization of the pulp would therefore be dependent on reduced blood supply to the remaining vital tissues and not necessarily the amount of reparative dentin formed with time

• It has been speculated that the material exerts a mitogenic and osteogenic effect, the high pH combined with the availability of calcium ions and hydroxyl ions has an effect on the enzymatic pathways and hence mineralization.

• The high pH may also activate alkaline phosphatase activity which is postulated to play an important role in the hard tissue formation.

• The optimum pH for alkaline phosphatase activity is 10.2, a level of alkalinity which is produced by many of the calcium hydroxide preparations.

The dentin bridge :

• A mineralized barrier or “dentin bridge” is usually produced following the application of calcium hydroxide to a vital pulp

• This repair material appears to be the product of odontoblasts and connective tissue cells.

• There appears to be some variation in the way the dentin bridge is formed, depending on the pH of the material that is used to dress the tooth.

• In the case of a high pH material necrotic zone is formed adjacent to the material and the dentin bridge then forms between this necrotic layer and the underlying vital pulp. The necrotic tissue eventually degenerates and disappears, leaving a void between the capping material and the bridge.

• In case of the material of lower pH, such as Dycal, the necrotic zone is similarly formed but is resorbed prior to the formation of the dentin bridge, which then comes to be formed directly against the capping material.

• Dentin bridges formed by the high pH materials are histologically similar to those produced by lower pH materials, but are easier to distinguish on a radiograph because of the space between the bridge and calcium hydroxide.

DISSOLUTION OF NECROTIC MATERIAL

The ability of calcium hydroxide to dissolve necrotic material was reported by Hasselgren et al. in 1988

Its action is similar to that of sodium hypochlorite but is less effective.

However, its prolonged presence in the root canal, where it has a continuous therapeutic effect, may largely compensate for this.

pH variation of calcium hydroxide on pulp tissue healing

high pH (11 to 13) - the original Ca(OH)2and water, Ca(OH)2 and saline or Pulpdent.

zone of obliteration - consists of debris, dentinal fragments, hemorrhage, blood clot ,blood pigment, and particles of Ca(OH)2.

zone of coagulation necrosis and thrombosis (the mummified zone). • (0.3 to 0.7 mm thick) represents devitalized tissue without complete

obliteration of its structural architecture. • Although the cellular detail is greatly diminished, outlines of capillaries

(filled with hemolyzed erythrocytes), nerve bundles, and pyknotic nuclei can still be recognized.

• Between the deepest level of the zone of coagulation necrosis and the subjacent vital-pulp tissue there is a line of demarcation.

• The coagulated necrotic layer causes a sufficient stimulation to the subjacent vital pulp tissue for it to respond with all its healing potential.

• The sequence of tissue reactions is basically that which is expected of wounded connective tissue, starting with vascular changes and inflammatory cell migration to control and eliminate irritating agents. The alkaline environment favors differentiation and replication of odontoblasts.

• As predentin is produced by the new odontoblastic layer forming subjacent to the line of demarcation, calcification soon occurs,

Healing with calcium hydroxide products of lower pH (9.0 to 10.0) (Life, VLC Dycal and Nucap etc): • Bridging at the CH-pulp interface occurs without the induction of a

visible intermediate coagulated necrotic layer, an indication of a less extensive 'initial chemical injury than that produced by the original Ca(OH)2 and water.

• May be one or two cell layers closest to the Ca(OH)2 dressing are affected but there is not enough tissue destruction to require an army of macrophages to carry off the dead and wounded cells and there is little need for any quantity of granulation tissue to fill in .

• Healing and regeneration occur right up against the Ca(OH)2 dressing. The capacity to make a more uniform dentinal bridge right up against the capping material is a great advantage.

Dental forumulation of calcium hydroxide pastes:

• Setting materials are generally used for the lining or sub-lining of the cavities, as root canal sealers.

• Non-setting cements are used for dressing root canals.

Vehicles for calcium hydroxide

Types of vehicles and their significance

Holland [1994] suggested a classification according to the vehicle of the paste. Aqueous, viscous, and oily

• When calcium hydroxide paste is mixed with a suitable vehicle, a high pH paste is formed and hence these formulations are known as alkaline pastes.

According to Maisto [1975], Goldberg [1982], these pastes should have the following characteristics :

• It should be composed mainly of calcium hydroxide which be used in association with other substances to improve some of the physicochemical properties such as radiopacity, flow and consistency.

• Should be non-setting.

• Should be rendered soluble or resorb within vital tissues either slowly or rapidly depending on the vehicle and other components.

• Should be prepared for the use at the chair side or be available as a proprietary paste.

• Should be used as only temporary dressing material and not as a definitive filling material

The easiest method to prepare a calcium hydroxide paste is to mix calcium hydroxide powder with water until the desired consistency is achieved.

However such a paste doesn’t have good physicochemical properties because

1.it is not radiopaque,

2.is permeable to tissue fluids and

3.is rendered soluble and resorbed from the periapical area and from within the root canal.

For these reasons and the following below, it is recommended that other substances be added to the paste.

• To maintain the paste consistency of the material which doesn’t harden or set.

• To improve the flow. • To maintain the high pH of calcium hydroxide; • To improve the radiopacity • To make clinical use easier • Not to alter the excellent biological properties of calcium hydroxide

itself.

The vehicle plays an important role in determining the velocity of theionic dissociation causing the paste to be solubilized and resorbed atvarious rates if any,in the periapical tissues and from with in the root canal. According to Fava [1991] an ideal vehicle should:

1. Allow gradual and slow release of Ca+ and OH-

2. Allow slow diffusion in the tissues with low solubility in the tissue fluids.

3. Have no adverse effect on the induction of the hard tissue deposition.

• The differences in the velocity of the ionic dissociation are related

directly to the vehicle employed to obtain the paste.

• The lower the viscosity the higher the ionic dissociation.

Vehicles used for Calcium hydroxide

According to Fava [1991] Holland [1994] the vehicles used are divided into

• Aqueous • Viscous • Oily

Aqueous • Water• Saline • Dental anaesthetics with or without vasoconstrictors. • Ringer’s solution. • Aqueous suspension of Methylcellulose or Carboxymethyl cellulose. • Anionic detergent solution.

Clinical importance :

• Ca2+ and OH- are rapidly released. • Promotes a high degree of solubility when the paste remains in direct

contact with the tissue and the tissue fluids causing it to be rapidly solubilized and resorbed by the macrophages.

• The root canal must be redressed several times until the desired effect is achieved there by increasing the number of appointments.

• Calxyl, Pulpdent and Tempcanal, Calvital, Reogan• Hypocal

Viscous : • Glycerin : 92.09382 g/mol• Polyethylene glycol • Prophylene glycol

Clinical importance :• Release calcium and hydroxyl ions more slowly for extended periods.

• They promote a lower solubility of the paste when compared with aqueous vehicles probably because of their higher molecular weights.

• The high molecular weight of these vehicles minimize the dispersion of the calcium hydroxide into the tissues and maintain the paste in the desired area for longer periods.

• This factor prolongs the action of the paste and calcium and hydroxyl ions will

be given off at lower velocity. It is through this mechanism that these pastes

remain in direct contact with the vital tissues for extended time intervals.

• Number of appointments and redressings of the root canal is drastically

reduced.

• Calen • Calen + camphorated parachlorophenol• Calen + p-chlorophenol

Ringers Lactate solution alkalinizes via its consumption in the citric acid cycle, the generation of a molecule of carbon dioxide which is then excreted by the lungs. They increase the strong ion difference in solution, leading to proton consumption and an overall alkalinizing effect. 

•Ringer's lactate solution was invented in the early 1880s by Sydney Ringer, a British physician and physiologist.

•osmolarity of 273 mOsm/L

•Ringer's Lactate solution is very often used for fluid resuscitation after a blood loss due to trauma, surgery, or a burn injury.

•Although its pH is 6.5, it is an alkalizing solution. R•ingers Lactate solution alkalinizes by its consumption in the citric acid cycle, leading to the generation of a molecule of carbon dioxide which is then excreted by the lungs.

•This increases the strong ion difference in solution, leading to proton consumption and an overall alkalinizing effect. 

Lactate: C3H6O3

Oily :

• Olive oil• Silicone oil• Metacresyl acetate• Some fatty acids such as oleic, linoleic ,isostearic acids

• Oily vehicles are non water soluble substances that promote the lower

solubility and diffusion of the paste with in the tissues.

• Pastes containing this kind of vehicle may remain with in the root canal

for longer periods than pastes containing aqueous and viscous

vehicles.

• Endoapex , Vitapex

• In cases of dental replantation, as soon a treatment is performed, a

paste of an aqueous vehicle is employed because of the need for rapid

ionic release and pH turnover to avoid replacement resorption.

• Subsequently, a calcium hydroxide paste with a viscous vehicle should

be used in the periodical redressings, because the paste may remain in

the root canal for longer period.

• Summarizing, clinical situations that require a rapid ionic liberation at the

beginning of the treatment require an aqueous vehicle containing

calcium hydroxide paste while in situations that require a gradual and

uniform ionic liberation, a viscous vehicle containing paste should be

used. (Pastes containing oily vehicles have restricted use)

Radiographic contrast media: • Calcium hydroxide mixed with any of the quoted vehicles lacks

radiopacity and is not easily seen radiographically. This is the main reason radiopaque materials are added to the paste, thereby allowing identification of lateral and accessory canals, resorptive defects, fractures and other structures.

• A radiopacifier should have an atomic weight higher than calcium for radiopacity purposes.

• Examples: • barium sulphate and bismuth• other compounds containing iodine and bromine

Antibiotics

• Quillmi et al (1992) suggested adding metronidazole and chlorhexidine to a calcium hydroxide paste and tested this formulation for its antibacterial effect.

• No statistically significant difference was found between Peridex and the combination of CaOH and Peridex. (J Endod. 2003 Sep;29(9):565-6)

• CHX was significantly more effective against E. faecalis than was Ca(OH)2 paste or a mixture of CHX with Ca(OH2 paste (p < 0.05). There was no increase in the efficiency of Ca(OH)2 paste when CHX was added (p > 0.05). (J Endod. 2005 Jan;31(1):53-6, Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006 Aug;102(2):e27-31)

• Chlorhexidine was found to be a better vehicle for calcium hydroxide when used as an intracanal medicament because of its low surface tension. (Dent Res. 2009 Jan-Mar;20(1):17-20)

Leonardo et al (JOE, 1999, vol25, 167-171) suggested that chlorhexidine prevents microbial activity in vivo with residual effects in the root canal system upto 48 hrs.

. 

CHLORHEXIDINE GLUCONATE• It has been used in dentistry since 1962. It is broad spectrum

antimicrobial agent.• It has antimicrobial activity against gram –ve & gram +ve

microorganisms.• The antimicrobial effect is related to the cationic molecule binding to

–vely charged bacterial cell walls, thereby altering the cell’s osmotic equilibrium.

• Its use in endodontics has been proposed as an irrigant as well as an intracanal medicament.

• When used as an intracanal medicament, chlorhexidine was more effective than Ca(OH)2 against E.faecalis infection in dentinal

tubules.

• Studies have shown that calcium hydroxide and CHX combination was more effective - Alexendra Almyroudi

• CHX is an excellent ICM when it is placed in the RC for one week - Richard Komorowski et al.

• Gomes et al ( OOO 2006) showed that 2% CHX gel & Ca(OH)2 has better antimicrobial activity than Ca(OH)2 manipulated with sterile water.

• Siren et al. reported that chlorhexidine increases the antiseptic action of calcium hydroxide

• Soares et al Due to its broad antiseptic spectrum, antibacterial substantivity, low surface tension, dentin diffusibility and relative low cytotoxicity, 2% chlorhexidine has been shown to be a promising vehicle for calcium hydroxide intracanal medication for endodontic treatment and re-treatment of teeth with pulp necrosis associated with periapical lesions.

• Concentration of 1 to 2% chlorhexidine combined with calcium hydroxide have also demonstrated efficacy at killing E. fecalis.

• Chlorhexidine combined with calcium hydroxide will result in a greater ability to kill E. fecalis than calcium hydroxide mixed with water (70)

• two percent chx gel combined with calcium hydroxide achives a pH of 12.8 and can completely eliminate the E. fecalis bacteria within dentinal tubules.

• Chx in root canals for 7 days can eliminate E.fecalis completely.• • Gomez b et al IEJ 2003 and evans MD et all JOE 2003•

Influence of the vehicle on the antimicrobial activity :

• Evidence suggests that the association of calcium hydroxide with CMCP has a broader antibacterial action, and kills bacteria faster than mixtures of calcium hydroxide with inert vehicles.

• Phenolic compounds such as CMCP possess strong antibacterial properties and halogenation intensifies its antibacterial properties.

• Phenol is believed to act by disrupting lipid containing bacterial membranes resulting in leakage of cellular contents.

• At higher concentrations, these components act by precipitating the cytoplasmic cell proteins.

• At lower concentrations these inactivate essential enzyme systems and may also cause bacterial cell lysis.

• Some properties of phenolic compounds, such as low surface tension and lipid solubility confer penetrability and spreading of the material

• Thus, the calcium hydroxide and CMCP mixture possesses a high radius of action, eliminating bacteria located in regions more distant from the vicinity where the paste was applied.

• Therefore CMCP cannot be considered as a vehicle for calcium hydroxide but an additional medicament especially against anaerobic bacteria such as a enterococcus faecalis.

Influence of different vehicles on the pH of calcium hydroxide pastes

“María Gabriela Pacios§, María Luisa de la Casa†, María de los Ángeles Bulacio† and María Elena López§

§Cátedra de Química Biológica, †Cátedra de Endodoncia, Facultad de Odontología”

Journal of Oral Science, Vol. 46, No. 2, 107-111, 2004

INTRODUCTION :Ca(OH)2powder for root canal dressing has been mixed with different vehicles such as distilled water, camphorated monochlorophenol (CMCP), normal saline, cresatin, glycerin and propylene glycol (PG.

Simon et al. (9) demonstrated that the vehicle can exert a great influence on the release of ions.

Sjögren et al. (12) demonstrated in vivothat Ca(OH)2dressings efficiently eliminate bacteria which may survive biomechanical instrumentation, and that reliable and predictable results can be achieved by dressing the canal with Ca(OH)2 for 7 days

AIM: The objective of this work was to determine the influence of the vehicle on the pH of calcium hydroxide pastes after usage in patients and in vitro.

Materials and Methods

In vitro study:

Ca(OH)2 pastes were prepared by adding to Ca(OH)2 powder (Anedra Lab., Buenos Aires, Argentina) to the following vehicles:

•distilled water,

• 0.2% chlorhexidine gluconate (ICN Biomedicals Inc, Ohio, USA),

•99.5% PG (Anedra Lab., Buenos Aires, Argentina),

•4% carticaine chlorhydrate (anesthetic solution; Totalcaina Forte, Microsules-Bernabó S.A., Lab., Buenos Aires, Argentina),• •11.8% CMCP (Farmadental Lab., Buenos Aires, Argentina) and

•11.8% CMCP-99.5% PG. The concentrations of the vehicles were evaluated quantitatively (13).

Using these pastes, aqueous solutions of Ca(OH)2 to a final concentration of 0.1 M were prepared in order to measure pH. These solutions were stored at 37°C in sterile tubes.

The pH was measured at 0, 1, 7, 14 and 21 days.

Clinical study :

180 maxillary incisors with pulp necrosis and radiographically visible chronic periapical lesions were selected. both sexes aged from 20 to 50 years considered.

After isolation with a rubber dam, carious tissue was removed from the teeth with a carver and a slow-speed handpiece.

The pulp tissue remaining in the canal was removed with K-files. working length : 15 K-file and radiographically monitoring the process.

BMP :step back technique up to a 45 or 50 master apical file. the canals were irrigated with 2 ml of 1% sodium hypochlorite

Teeth were filled using the last K-file employed in the canal preparation, aided by absorbent paper points and vertical pluggers.

The access cavities were closed with Cavit (Espe, Seefeld, Germany) and glass ionomer restorative cement (Fuyi II, GC Corp., Tokyo, Japan).

The temporary pastes were retained in the root canal for periods of 7, 14 and 21 days.

Patients were randomly divided into six groups each containing 30 teeth.

The paste fillings were prepared from Ca(OH)2 powder and the same vehicles employed in the in vitro study (distilled water, 0.2% chlorhexidine gluconate, 99.5% PG, 4% carticaine chlorhydrate, 11.8% CMCP and 11.8% CMCP- 99.5% PG).

At each time point, 10 pastes from each group were removed with K-files and collected in separate Eppendorf tubes previously weighed on a precision scale (Acculab LA-Series Analytical Balances, Newtown, Canada).

The tubes with the pastes were re-weighed and the difference between the initial and final weights was calculated.

In this way the weight of the extracted paste from the root canal was obtained.

Then the pastes were dissolved with distilled water to a final Ca(OH)2concentration of 0.1 M, according to the following formula:

volume of distilled water added (ml) = weight of the paste (g) / 0.0741 (mMW of Ca(OH)2) × Ca(OH)2 concentration (0.1 M).

The solutions were used to obtain pH measurements.

pH measurement :

The pH was determined with a digital pH meter (Broadley-James Irvine, California, USA) for small volumes (sensitivity: 0.01 pH units), calibrated to pH 7 and 4 with standard buffer solutions before use.

The pH was determined by placing the refillable calomel electrode in a 15-µl sample on a slide for 10 seconds.

The electrode was washed with distilled water and wiped dry between readings.

Result:

No significant difference in pH was found for the different time intervals.

However, significant differences in pH were observed among the pastes tested.

Dunnett’s T3 multiple range test showed no significant differences among the Ca(OH)2 pastes with distilled water, chlorhexidine, PG and anesthetic solution,

but statistically significant differences were observed between these pastes and those containing CMCP and CMCP-PG.

Discussion:

Calcium release and an alkaline pH are extremely important for the biological and microbiological performance of the material for dental use.

In this study, no difference in the pH of each of the Ca(OH)2 pastes was observed over time.

The tested pastes maintained their alkalinity even in an Eppendorf tube (in vitro study) as in the clinical study.

In vitro, pastes with chlorhexidine, PG and anesthetic solution showed a similar pH to those containing distilled water.

However, in the clinical experiment the pH of the paste containing distilled water was significantly different from the other pastes.

In the present study, vehicles used to prepare the Ca(OH)2 pastes were shown to influence the final pH of the pastes.

CALCIUMHYDROXIDE

ROOTCANAL

SEALER

LINER

INTRACANAL

MEDICAMENT PREVENTIONOF

RESORPTION

BASE

INDIRECTPULP

CAPPING

DIRECTPULP

CAPPINGPULPOTOMY

APEXIFICATION

HORIZONTALROOT

FRACTURE

PERFORATIONREPAIR

RESORPTIONREPAIR

1. Calcium hydroxide as liner

• The basic component of liner is calcium hydroxide. Calcium hydroxide is dispersed in aqueous or resin solution so that the liner can be applied to the cavity in relatively thin films.

• The solvent evaporates, leaving a layer of calcium hydroxide on the cavity walls.

• It is mandatory that the margins of the cavity preparation be kept free from moisture for this type of liner, since calcium hydroxide is soluble in oral fluids.

The setting calcium hydroxide pastes are now in general use as Lining materials.

Their perceived advantages, in addition to their therapeutic effects, are as follows;

1. They have a rapid initial set in the cavity under the accelerating effect of moisture in the ambient air of the oral cavity and from within the dentinal tubules.

2. They do not interfere with the setting reaction of Bis-GMA resins, and are therefore the lining material of choice under composite resin materials

3. It is generally considered that the initial set of the material in thin sections is sufficiently hard to resist the applied condensation pressures that are required even for lathe cut amalgam alloys

4. It has been shown that the light-cured resins are biocompatible and will not cause pulpal damage. However, it is possible that detrimental effects may occur, particularly in deep cavities close to the pulp, as a result of the effects of heat generated during seating.

• The disappearance of the early versions of these materials from beneath restorations was probably due to the effects of bacteria and microleakage.

2. As a sub base and a base• As a sub base it provides therapeutic properties- helps in repair of pulpal tissue- provides chemical insulation.• have specific pharmacological action.• should be covered with supporting base as they have low strength

• Ca (OH)2 Bases are of relatively low strength and used only for their therapeutic effect.

(Sub base: Therapeutic materials placed in deep portion of the cavity preparation.

•Hard setting materials have usually been employed. The most commonly used material is Dycal.  The formula of Dycal in 1975 was given in accepted dental therapeutics.

 CATALYST PASTE • Calcium hydroxide - 51.00• Titanium diaoxide -45.10• Zinc oxide -9.23• Zinc stearate -0.29• Ethyl toluene Sulphonanfide -

39.48

BASE PASTE • Titanium dioxide -45.10• Calcium tungstate - 15.20• Calcium hydroxide - 0.60• Glvcol salicylate - 39.10

AS A BASE:

• Fisher and McCabe (1978) noted that the titanium dioxide in the base paste consisted of 1/3 titanium dioxide.

The Current Composition of Dycal isCATALYST PAST %

• Calcium hydroxide 51.16Zinc oxide 9.21Titanium Dioxide 4.74Ethyl tolueneSulphonamide 39.73

BASE PASTE• Calcium phosphate 31.4 • Calcium Tungstate 17.63 • Zinc oxide 8.70 • Butyl glycol Disalicylate 42.27

Calcium hydroxide for pulp protection : • Indirect pulp treatment & direct pulp treatment• Mainly by the formation of dentin bridge

Calcium hydroxide in pediatric endodontics : Pulpotomy : • Historically, calcium hydroxide was the first medicament used in the

“regenerative” capacity because of its ability to stimulate hard tissue barrier formation.

• Recently, its regenerative capacity has been questioned owing to the fact that the calcium hydroxide is more reactive than inductive.

• The failures were in the form of chronic pulpal inflammation and internal resorption.

Internal resorption may result from the over stimulation of the primary pulp by the highly alkaline calcium hydroxide.

This alkaline – induced over stimulation could cause metaplasia within the pulp tissue, leading to the formation of odotnoclasts.

In addition, undetected micro leakage could allow large numbers of bacteria to overwhelm the pulp and nullify the beneficial effects of calcium

• Contradicting to this, it is seen that some low pH commercial preparations of calcium hydroxide, showed earlier and more consistent bridging.

• Many extensive studies on calcium hydroxide concluded that the state of the pulp, surgical trauma, or the amputation treatment could be important than the calcium hydroxide per se in inducing success.

• At present, generally it is not recommended for primary teeth owing to its low success rate but due to difference in cellular anatomy , it is recommended for young permanent teeth

• The improved clinical outcomes with the use of calcium hydroxide in young permanent teeth make it the most recommended pulpotomy agent for carious and traumatically exposed teeth.

• Its use is of particular importance in incompletely formed apex (Apexogenesis and Apexification()

Calcium hydroxide as a root canal filling material for primary teeth.

• Studies have shown that calcium hydroxide is the material of choice for the primary teeth as it shown to have less periapical reaction when the material extrudes beyond the apex, when compared to the materials.

• Though it is thought to resorb faster than the root (not very significant), it is said that it creates a sterile environment in the canal thereby inhibiting the infectious process.

• • The common commercial calcium hydroxide preparations used as a

filling material are Vitapex etc

Apical plug :• In situations where there is an open apex or abnormal

apical anatomy, the dentin chip plug in the periapical tissue has been advocated as an artificial but biological apical stop against which gutta-percha can be condensed.

Dressing of the root canal :• It is doubtful whether a routine calcium hydroxide dressing is

necessary for the root canal therapy in the canals that contain vital pulp tissue as these are not infected prior to the instrumentation, or in contaminated canals which have been cleaned and shaped with modern instrumentation techniques. However, if a root canal is heavily infected prior to instrumentation, it is highly probable that a few bacteria will remain. In these circumstances, a dressing with calcium hydroxide which can be placed the full length of the canal is the treatment of choice.

Long-term temporary dressing :

• When a dressing is placed in the root canal it is removed after a few days and the root canal permanently filled with gutta-percha. On occasion it is necessary, for reasons of personal convenience, to leave the dressing in the root canal for a considerable period of time. Under these circumstances calcium hydroxide may be regarded as the dressing material of choice because its antimicrobial effect may last for longer duration.

Treatment of infected root canals and periapical lesions :• Periapical granulomata may be formed by the immunological

responses of the apical tissues to chronic infection within the root canal.

• When small they are sterile, but as they increase in size they may contain in increasing variety of bacteria. In such cases it seems reasonable to use a dressing which can be placed as close to the lesion as possible.

• Calcium hydroxide can be used as a root canal dressing in teeth with large periapical lesions, and in cases where it is necessary to control the passage of periapical exudates into the canal.

• Calcium hydroxide accelerates the natural healing of periapical lesions, regardless of the bacterial status of the root canal at the time of placement of the material.

Calcium hydroxide in the prevention of root resorption :Idiopathic :• Calcium hydroxide is frequently used as a dressing for the treatment of

both the internal and external inflammatory resorption, in order to halt the process and encourage remineralization.

• It is doubtful whether the material has any real beneficial effect on internal resorption, as this is now considered to be sustained by infection within the dentinal tubules coronal to the resorptive process. At one time it was thought that the osteoclasts and osteocytes originated from the same progenitor cells, and that osteoclasts could divide into osteoblasts, presumably under the influence of calcium hydroxide. However, it is now considered that these two cell types have different origins.

• Whether the resorption is external, or internal with communication to

the periodontal membrane, calcium hydroxide is probably the initial treatment of choice, and used in the same manner as for apexification.

Treatment of weeping canals :

Calcium hydroxide is now widely used to reduce the seepage of apical fluids into the canal so as to allow the placement of a satisfactory root filling.

The mechanism whereby the reduction of the seepage occurs is probably due to :

The formation of a fibrous barrier when calcium hydroxide is placed in direct contact with the host tissues.

Acidic pH of periapical tissues is converted to more basic environment.

Following the replacement of an avulsed tooth, or transplantation of a tooth • Once an avulsed tooth has been splinted in position for about two

weeks the root canal should be thoroughly cleaned and dressed with calcium hydroxide for a period of 3-6 months, prior to the placement of a conventional root canal filling.

• One should note that the immediate placement of calcium hydroxide may stimulate early resorption.

• This is because calcium hydroxide diffuses through the apical foramen, further injuring the cementum and initiating resorption.

• Calcium hydroxide treatment has no effect on the replacement (ankylosis) once it has been established.

• The principles of managing the transplanted teeth, once pulpal necrosis has been confirmed, are essentially the same as those that relate to replantation.

   Calcium hydroxide as a root canal sealer :

• Calcium hydroxide – based root canal sealers which have introduced as an alternative to the conventional zinc oxide eugenol – based sealers are Sealapex and Calcioboitic Root Canal Sealer (CRCS).

• The rationale for the use of these materials is that if they are used in canals with wide apical foramina, perforations or fractures, mineralized repair may further be induced.

CRCS: Calcibiotic root Canal Sealer

Powder: Calcium Hydroxide Zinc oxide

Bismuth dioxideBarium sulphate

Liquid: EugenolEucalyptol

Sealapex:Base: Calcium Hydroxide 25.0%

Zinc Oxide 6.5%

Catalyst: Barium Sulphate 18.6% Titanium dioxide 5.1%

Zinc Stearate 1.0%

vitapex

Calcium hydroxide` 30%

Iodoform 40.4% BacteriostaticIncreased radiopacity

Silicone Oil 22.4% Lubricant, ensures complete coating of(Medical Grade) canal wall

• When the pattern of release of calcium ions and hydroxyl ions from different sealers was investigated, it was found that Sealapex released more ions and disintegrated more rapidly than CRCS.

• It was also found that, although the release of calcium ions from CRCS was negligible, the material continued to alkalize its environment, possibly due to the free eugenol combining with calcium ions as they were released.

• In this context it is important to note that , whether these root canal sealers promote a quicker healing or a more predictable tissue response than non-calcium hydroxide sealers, has not yet been evaluated.

Miscellaneous applications of calcium hydroxide :• As a dentin desensitizing agent • As a micro leakage demonstrator

Advantages of Calcium hydroxide

Initially bactericidal to bactertiostatic

Promotes healing and repair

High pH stimulates fibroblasts

Neutralizes low pH of acids

Calcium hydroxide stimulates enzyme systems

Drops internal resorption

Most ideal endo intracanal medication

Inexpensive and easy to use

Particles may obturate open tubules

Ideal temporary luting cement 

Disadvantages of Calcium hydroxide

Does not exclusively stimulate dentinogenesis

Does not exclusively stimulate sclerotic dentin formation

Does not exclusively stimulate reparative deposition

Does not exclusively stimulate dentin bridge formation

Does not exclusively stimulate Apexification

Associated with primary tooth root resorption

May dissolve after one year with cavosurface microleakage

Acids may degrade the interface during the tubules etching process

Interfacial failure upon amalgam condensation

Association with recurrent caries upon loss seen in tunnel defects of

bridges after one year placement

Does not adhere to vital dentin

Does not adhere to bonding resin composite systems.

Unlike eugenol, calcium hydroxide is not a pulpal anodyne.

CONCLUSION• Calcium hydroxide has been around the century and the research

surround it’s properties and use, has increased dramatically in the recent years.

• Many newer materials are now available in the market, which claim to be superior to calcium hydroxide.

But how possible is the use of these materials in the Indian scenario?

• When compared to the prices of the newer materials calcium hydroxide is more cost effective.

• Some preparations of calcium hydroxide are still, expensive but a simple calcium hydroxide powder and sterile water can serve many purposes and works out to be reasonable and affordable to many patients who visit the Indian dental clinics.

• One must also consider the ease in manipulation and the time factor associated with the calcium hydroxide preparations.

• Although calcium hydroxide has become one of the most widely accepted materials in the dental office as a solution to most of the problems if not all!!!.

What makes calcium hydroxide so special to dentistry ???

antibacterial property + property of inducing a hard tissue barrier

= an elixir of life for the dying teeth!

ReferencesText book references:• Pathways of the pulp –Stephen Cohen ,8th and 9th editions

• Endodontics – Ingle & Bakland 5th & 6th edition

• Principles and practice of endodontics-Walton and Torabinezad 4th

edition

• Endodontic science Volume 12 – Carlos Estrela

• Phillips’ science of dental materials – 11th edition

• Operative dentistry – Marzouk.

Journal references• Evaluation of pH and calcium ion release of calcium hydroxide

pastes containing different substances.

- J Endod. 2009 Sep;35(9):1274-7.

• Mechanisms of antimicrobial activity of calcium hydroxide: a critical

review - International Endodontic Journal, 32, 361±369, 1999.

• Comparative evaluation of the surface tension and the pH of

calcium hydroxide mixed with five different vehicles: an in vitro

study. - J Dent Res. 2009 Jan-Mar;20(1):17-20

• Antimicrobial efficacy of chlorhexidine and two calcium hydroxide

formulations against Enterococcus faecalis.

-J Endod. 2005 Jan;31(1):53-6

• A comparison of the surface tension of calcium hydroxide mixed

with different vehicles

- J Endod. 2000 Sep;26(9):500-2

• Calcium concentration and pH of the periapical environment after

applying calcium hydroxide into root canals in vitro.

- J Endod. 2001 May;27(5):343-6.

• Effectiveness of selected materials against Enterococcus faecalis:

part 3. The antibacterial effect of calcium hydroxide and

chlorhexidine on Enterococcus faecalis

- J Endod. 2003 Sep;29(9):565-6

• In vitro assessment of the effectiveness of chlorhexidine gel and calcium

hydroxide paste with chlorhexidine against Enterococcus faecalis and

Candida albicans.

-Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2006 Aug;102(2):e27-

31.

• Influence of different vehicles on the pH of calcium hydroxide pastes. - J

Oral Sci. 2004 Jun;46(2):107-11

• Investigation of pH at different dentinal sites after placement of calcium

hydroxide dressing by two methods

-Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2005 Apr;99(4):511-6

• Particle size and shape of calcium hydroxide - J Endod. 2009 Feb;35(2):284-7.

• pH changes in root dentin after intracanal placement of improved calcium hydroxide containing gutta-percha points.

J Endod. 2003 Jan;29(1):4-8

• Calcium hydroxide pastes: classification and clinical indications International Endodontic Journal, 32, 257±282, 1999.

• Solubility and biocompatibility of calcium hydroxide-containing root canal sealers

Dental tramataulogy ,vol 4 , issue 4 ,Pages 152 - 159,

• A review of Calcium hydroxide – IEJ 1990, 23, 283-297

• Calcium hydroxide: study based on scientific evidencesJ. Appl.Oral Sci.Vol.11,no.4,oct/Dec 2003

Thank you