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INTRODUCTION During the last 200 years there has been many changes in the rational governing the treatment of exposed dental pulps for years this has been subject to change and controversy. At the same time, pulp medicaments have survived these controversial years. A better understanding of the reactions of the pulp and dentin to these medicaments has developed over time, primarily through improvements in histologic techniques. Introduction of CaOH 2 started a new epoch in the treatment of dental pulp. This extensive usage however is not matched

by

clear

understanding

how

CaOH 2

promotes

osteodentin bridge formation nor its putative antibacterial activity. Since that time combinations of CaOH 2 have been used with much success not only in capping pulps but also in other reclammatory endodontic procedures. CaOH 2 act as a protective barrier for pulp tissues not only by blocking patent dentinal tubules but also protects the pulp from subsequent irritation by rehousing in a closed chamber but

1


also by neutralizing (pH 12.2), the attack of inorganic acids and leached products from certain cements and restorative materials. The applications of CaOH 2 within restorative and endodontic procedures have widened with great change of preparations. HISTORY History relates that trial and error had been the order of the day and one of the first to recognize the advantage of medicament was W.H. Atkinson (1866) spoke of the advantages of not exposing the pulp and reported leaving softened dentin over a vital pulp and sealing it with creosote. Louis Jack (1873) was thinking in term of preserving the vitality of the pulp a century ago. A. Witzel (1874) introduced the deliberate amputation of the infected portion of the pulp as a therapeutic measure. He believed that the entire coronal portion of the pulp should be removed and the remaining shimps covered with an

2


antiseptic. (He procured weak phenol solution) to destroy bacteria and to prevent decomposition. Witzel maintained that pulps healed by formulation of scar tissue. E.A. Hunter (1883) suggested this formula for pulp capping. Sorgum molassum; droppings of English sparrow – He claimed 98% success with it. J.F. Foot (1886) suggested that the best conveying for the amputated pulp was a blood clot. Frigoletta noted that small exposures and a good blood supply have the best healing potential. In 1891, Miller discussed various antiseptics that should be used for sterilizing dentin. Calcium hydroxide (calxyl) was introduced in the 1920’s for a substance that was biologically compatible with pulpal and periodontal tissues. He was not content with the available cytotonic medicaments that he thought would generate and perpetuate various lesions of endodontic origin.

3


In 1930 Hermann advocated using calcium hydroxide for pulp capping, pulpotomy and treatment of infected canals. In 1938 Teuscher and Zander introduced CaOH 2 in USA, as a pulpotomy agent. CaOH 2 pulpotomy was most favored in the 1940’s and 1950’s because it was felt to be more biologically acceptable material maintaining pulp vitality and promoting a bridge of reparative dentin. This rationale was introduced by Teuscher and Zander and termed as ‘Vital Technique’. Among the materials recommended to promote healing of accidental or pathologic exposure have been asbestos, plaster of paris, powdered ivory, tissue paper, and Canada balsam, septic spounge, vulcanized rubber cork, oil silk, galt nuts, busmas, pulverized glass, borax, cappings of gold foil, thymol crystals, powdered dentin or bone. Pure or mixed antiseptics, antibiotics corticosteroids formaldehyde, zinc oxide. In

addition

there

are

number

of

preparations with known and unknown formulae: 4

commercial


CLASSIFICATION AND TYPES CaOH 2 containing pastes can be classified according to whether they are setting or non-setting materials. The former are generally used for the lining or sub-lining of cavities, or as root canal sealers, while the latter are used for dressing root canals. SETTING MATERIALS Strong effect: -

Dycal (original formula)

-

Reocap

-

Procal

Medium effect: -

Dycal (New formula)

-

Life

-

Renew

-

Reolit.

No effect: -

M.P.C.

-

Hydrex

-

Cal-Mer- VII 5


Non-setting materials: -

Analar Ca(OH 2 ) – H 2 O

-

Pulp dent methyl cellulose

-

Hypocal methyl cellulose

-

Reogan methyl cellulose

SETTING MATERIALS The

therapeutic

properties

of

the

setting

CaOH2

materials are related to their pH. The latter is dependant on the levels of unbound calcium and hydroxyl ions that remain after the material has set and it follows that the egress of ions from the set material will lead to a reduction its mass. One factor which increases the availability of the hydroxyl ions is the hydrophobic nature of the material. The more hydrophobic the latter, the less likely is the diffusion to occur. A new withdrawn product, hydrox for ex was more hydrophobic than dycal due to the presence of paraffin solvent which prevented the diffusion of material in the set material. An additional factor to be considered in the dissolution of Ca(OH) 2 is the effect of bacteria, associated with 6


microleakage, on the set material (Watts and Patterson 1987). Established that bacteria may be present in contact with CaOH 2 . This could lower the pH of the material by converting it to calcium carbonate, and might explain why early dycal preparation seemed to disappear from beneath permanent restorations. It is possible to rank the setting CaOH 2 paste according to the availability of their hydroxyl ions. This ranking also corresponds with the antibacterial activities of the materials. It is evident that if antibacterial activity is required (as in DPC) the paste should be selected from near the top of the list, where diffusion of hydroxyl ions is greatest. Whereas if an antibacterial effect is not required (when the material is to be used newly as a lining). The CaOH 2 paste should be selected from near the bottom of the list because such materials are less likely to leak out from beneath the restoration. The rationale for inclusion of CaOH 2 in such non-therapeutic materials where its high antibacterial

7


effect is not required is said to be its ability to react readily in the setting process. SETTING

MECHANISM

OF

CaOH 2

CONTAINING

MATERIALS There are two basic setting mechanisms: 1.

The two paste system: Is based on the reaction between calcium and zinc ions

and a salicylate chelating agent and is accelerated by presence of H 2 O. 2.

The single paste system: This utilizes the polymerization of a dimethacrylate by

means of visible light and is represented by Prisma V.L.C. Dycal.

A potential disadvantage

of

the

dimethacrylate

systems, when used as a base beneath composite restoration, is their adherence to the composite material and subsequent withdrawal

from

the

base

of

the

cavity

during

polymerization. CaOH 2 materials have also been developed for use as root canal sealers (calcibiotic root canal sealer, sealapex). In 8


these preparations the setting time is increased probably by replacing CaOH 2 with calcium oxide in order to allow adequate time for the gutta-percha root filling to be condensed. NON-SETTING MATERIALS Most simply, Analar CaOH 2 may be applied either dry, or using distilled H 2 O as the vehicle. Clinically this has the disadvantage that the mixture forms a slurry which may separate and can be difficult within the root canal by putting alternatively, it may be mixed into a very thick paste which can be placed in the root canal with an amalgam carrier and condensed with root canal pluggers. Proprietory branch over came this problem by using methyl cellulose as a vehicle with varying amounts of water. This results in homogenous pastes of varying consistency, with good handling properties such as neogan. Other anaesthetic

admixtures solution,

have

been

camphorated

suggested

as

local

monochlorphenol,

beechwood creasote, ledermix and radiopacifiers with the possible exception of the last where barium sulphate may be 9


mixed with Ca(OH) 2 in a ratio of 1:8. These mixtures are now out of favour because the additives may achieve very little and indeed could adversely influence the beneficial effects of Ca(OH) 2 . CLASSIFICATION: Ca(OH) 2 preparations can be classified according to their mode of delivery. a. Dry powdered Ca(OH) 2 . b. Single paste system. c. Two paste system. d. Root canal sealer. A. Dry powdered Ca(OH) 2 - Ex: Analar Ca(OH) 2 , Reogan. This is available as a dry Ca(OH) 2 in powdered form which can be used mixing it either with: -

Distilled water.

-

Saline

-

Glycerine.

-

L.A solution without vasoconstrictor.

-

Methyl cellulose.

10


These solutions help as carriers / vehicles for easy placement of the material. B. Single paste System – Eg: Hypocal, Prisma V.L.C. Dycal etc. These are available as single paste which can be used directly. But Prisma V.L.C. Dycal utilizes light for the polymerization of the material to set. C. Two paste system – E.g.: Alkaliner, Dycal, Basic. These system contains an acid paste and a base paste. This setting reaction based on the reaction between calcium and zinc ion and a salicylate chelating agent and is accelerated by the presence of water. D. Root canal sealers – E.g. : Sealapex, Calcibiotic root canal sealers (CRCS). In these preparations the setting time is increased, probably by replacing Ca(OH) 2 with calcium oxide, in order to allow adequate time for the gutta-percha root filling to be condensed.

11


COMPOSITION: The constituents and the proportions of commercially available Ca(OH) 2 cements vary from product to product. De Frietas and Prosser et al (1982) have characterized Ca(OH) 2 preparation based on their results. a. ALKALINER Acid paste -

Organic components – Salicylate ester.

-

Inorganic filler – Barium sulphate.

Base paste -

Inorganic component – Calcium hydroxide.

-

Plasticizer – A sulphonomide.

b. BASIC Acid paste -

Organic component – Salicylate ester

-

Inorganic filler – Barium sulphate.

Base paste -

Inorganic component – Ca(OH) 2

-

Plasticizer – A sulphonamide 12


c. DYCAL ADVANCED FORMULA II Acid paste -

Organic components – Methyl salicylate ester.

-

Inorganic fillers o Titanium dioxide. o Calcium sulphate. o Calcium tungsten. o Alumina

Base paste Inorganic components -

Calcium hydroxide.

-

Zinc oxide.

Plasticizers -

Ortho and Para 4-ethyl toluene.

-

Sulphonamide

d. HYDROXYLINE TC Liquid varnish preparation of methyl / ethyl / ketone / acrylic polymers with Ca(OH) 2 and titanium dioxide and other constituents.

13


e. LIFE Acid paste Organic component – salicylate ester Inorganic filler -

Titanium dioxide.

-

Barium sulphate.

-

Alumina.

Base paste Inorganic components -

Calcium hydroxide.

-

Zinc oxide.

Plasticizer - Diethyl – para – toluene sulphonamide. f. VLC DYCAL Acid paste Organic component – Urethene dimethacrylate resin. Inorganic filler – Barium sulphate.

14


Base paste Inorganic components -

Calcium hydroxide.

Plasticizer -

None

g. HYDREX (withdrawn) Acid paste Organic component -

Isobutyl salicylate ester.

-

Modified solution (abietic acid derivatives)

Inorganic filler -

None

Base paste Inorganic components -

Ca(OH) 2

-

Zinc oxide

-

Barium sulphate

-

Titanium

Plasticizer -

Paraffin oil 15


h. MPC (withdrawn) Acid paste Organic component -

Isobutyl salicylate ester.

-

Modified resin

Inorganic filler -

None

Base paste Inorganic component -

Ca(OH) 2

-

Barium sulphate

-

Titanium dioxide

Plasticizer -

Paraffin oil

PHYSICAL AND CHEMICAL PROPERTIES Like all other dental cements, Ca(OH) 2 cements set by an acid-base reaction, the phenolic group in the alkyl salicylate ester acting as an acid once set, upon the release of calcium (Ca + 2 ) and (OH - ) hydroxyl ion which can only occur if the cement is water soluble. 16


It is the nature of the plasticizer that imparts this solubility. Currently most cements set by some of the available Ca(OH) 2 reacting with the salicylate ester chelating agent in the presence of a toluene. Sulphonamide plasticizer. The later is hydrophilic and soluble. The set cement contains a matrix of calcium-alkyl salicylate

chelate

and

excess

unreacted

Ca(OH) 2 .

The

fragility of the set cement suggests that the chelate are held by together by weak secondary attractions rather than a stronger polymeric structure. Most of the commonly used two paste systems Dycal, Life and Alkaline utilizes this chemistry. Any lining material when subjected to an acid should be non-permeable and remain unaltered McComb (1983) found Procal to be most susceptible than Life. Burke and Watts (1986) found that Dycal lost a significant percentage of mass than Life, MPC. Procal MPC was least prone to acid dissolution due to paraffin oil (plasticizer) and aqueous dissolution.

17


Liner material are required to have certain properties, typically strength, thermal insulation and rapid development of strength. However, there is little agreement in literature on optimal strength of the liner material. Ca(OH) 2 has a greater strength and modulus of elasticity when used as a liner but the material is markedly weaker than dental cements. Studies have suggested that Ca(OH) 2 develops a maximum strength at 7 min. with no significant increase after 30 minutes or at 24 hours. Further, it has been stated that Ca(OH) 2 liners are not displaced or fractured by amalgam condensation 7 minutes after placement. While the inherent weakness of the Ca(OH) 2 liners can be compensated by increasing layer thickness during

use.

It

has

been

shown

that

the

fracture

of

conventional and high copper amalgams is decreased by as much as 50% when the thickness of the liner is increased from 0.5 to 1mm. Recently new calcium hydroxide liner materials have been introduced to the dental profession, while one widely used material has been improved by the manufacturer.

18


There is uncertainty in the literature over the ideal strength of a liner material when the optimum test method for assessing the strength characteristic were used. Based on certain studies in could appear that only Life, Dycal and Renew have adequate strength at a thickness of 1 mm after 7 minutes. Liner thickness grater than 1 mm may not be acceptable in clinical situations where high liner strengths with minimal space filling is required. Baker

and

Wilson

(1968)

found

that

24

hours

compressive strength of: Life – 7.81MN/mm 2 . Dycal – 8.2MN/mm 2 These fully set cements are insufficient to withstand the average condensation pressure of amalgam, which is 10.5 MN/mm 2 . However, Hydrex and MPC had a hydrophobic paraffin as

plasticizer

and

hydroxyline-methyl

alcohol

ketone

solution of methyl methacrylate. Both Hydrex and MPC have been shown to be relatively

less

insoluble

and 19

have

poor

antibacterial


properties in vitro and have since been withdrawn from the market. Hydroxyline is marketed as resistant to acid etch pressure. Since it is highly insoluble and consequently the therapeutic potential is limited. MODE OF THERAPEUTIC ACTION Biochemical Actions It seems that Ca(OH) 2 has the unique potential to induce mineralization, even in tissues which have not been programmed to mineralize. However studies could not verify that Ca(OH) 2 induced mature bone formation under these circumstances, but found that when the material was placed in direct contact with host tissue, it induced the formation of fibrous tissue with the occasional formation of areas of immature bone. They also found that when Ca(OH) 2 was separated from host tissue by Millipore filters no significant reaction occurred, indicating that the material did not have any effect once it had diffused to some distance. It is also likely that the calcium ions present in the applied

Ca(OH) 2

do

not

become 20

incorporated

in

the


mineralized repair tissue which derives its mineral content solely from the dental pulp, primarily via the blood supply. These

observations

indicated

that

calciumhydroxide

an

initiator rather than a substitute for repair. The

mechanism

by

which

Ca(OH) 2

initiates

the

reparative process is unclear. It has been suggested that a rise in pH as a result of the free hydroxyl ions may initiate mineralization. Ca(OH) 2 may also act as a local buffer against the acidic reactions produced by the inflammatory process. An alkalinic pH may also neutralize the lactic acid, secreted by osteoclasts, and this may help to prevent further destruction of mineralized tissue. It has been speculated that the material exerts a mitogenic and osteogenic effect. The high pH combined with the availability of Ca and OH- ions have 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 hard tissue formation. 21


The optimum pH for alkaline phosphatase activity is 10.2 a level of alkalinity which is produced by many Ca(OH) 2 preparations. Studies suggested that calcium ions may reduce the permeability of new capillaries, so that less intercellular serum is produced, thus increasing the concentration of calcium ions at the mineralization site. The presence of a high calcium concentration may also increase the activity of calcium dependant pyrophosphatase, which represents an important

part

of

the

mineralization

process,

once

mineralization has been initiated it can continue unabated if the normal self limiting enzymes fail to operate. The reduced capillary permeability following the increase in the number of calcium ions could reduce serum flow within the dental pulp and consequently the concentration of the inhibitory pyrophosphate ion would be reduced. This would coincide with

an

increase

pyrophosphate

and

in

levels would

mineralization of the pulp tissue.

22

of

calcium

result

in

dependant uncontrolled


Ca(OH) 2 Ca 2

OH

Reduced capillary permeability

Neutralizes acid produced by osteoclasts

Reduced serum flow

Optimum pH for pyrophosphatase activity

Reduced levels of inhibitory pyrophosphate

Increased levels of Ca 2 + dependant pyrophosphatase Uncontrolled mineralization

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

23


The Dentine Bridge A mineralized barrier of “Dentine Bridge� is usually produced following the application of Ca(OH) 2 to a vital pulp. This repair material appears to be the product of odontoblasts and C.T. cells. These appears to be some variation in the way in which a dentine bridge is formed depending on the pH of the material that is used to acess a tooth. In case of a high pH material such as pulpdent a necrotic zone is formed adjacent to the materials and the dentine bridge then forms between this layer and the underlying

vital

pulp.

The

necrotic

tissue

eventually

regenerates and disappears, leaving a void between the capping material and the bridge. In the case of material of lower pH such as dycal, the necrotic zone is similarly formed but is resorbed prior to the formation of the dentine bridge, which then comes to be formed directly against the capping material.

24


Dentine bridges formed by the high pH materials are histologically identical to those produced by lower pH materials, but are easier to distinguish on a radiograph because of the space between the bridge and the calcium hydroxide. Antibacterial Activity Some of the healing properties of Ca(OH) 2 may be attributed to its bactericidal effects. The bactericidal properties of Ca(OH) 2 are thought to be directly related to pH and are directly proportional to the ability of Ca(OH) 2 to diffuse from the set material. Applications 1. Vital pulp therapy. a. Direct pulp capping. b. Indirect pulp capping. c. Pulpotomy. d. Apexogenesis. 2. Routine intracanal dressing between appointments. a. Routine dressing. b. Long-term temporary dressing. 25


3. Large periapical lesions. 4. Treatment of divergent apex in a pulpless tooth (Apexification). 5. Control of persistent apical exudates into the canal. 6. Prevention of root resorption. a. Idiopathic. b. Following the replacement of an avulsed tooth, or transplantation of a tooth. 7. Repair of iatrogenic perforations. 8. Treatment of root fractures. 9. Constituents of root canal sealers. 10. Dentine desensitizing agent. 11. Microleakage demonstrator. Direct Pulp Capping Direct pulp capping is undertaken in an attempt to maintain the health of an exposed vital pulp. The advent of the setting materials simplified the placement of Ca(OH) 2 because no further reinforcement was necessary. 26


The following criteria must be observed if successful DPC is to be achieved. 1. There must be no symptoms of pulpitis, if Ca(OH) 2 is used to cap an inflamed pulp necrosis will probably occur due to the presence of bacterial infection. 2. In case of carious exposure, there is general agreement that the larger the exposure the poorer the prognosis because

of

magnitude

of

contamination

by

microorganisms. In the case of traumatic exposure with no bacterial contamination, the size of exposure is immaterial. 3. Bacterial

contamination

from

saliva

should

be

prevented if possible. 4. Young permanent teeth are more successfully treated than elder permanent teeth because of the open apical foramen and the improved blood supply to the pulp. Indirect Pulp Capping Residual carious dentine left in the tooth cavity probably contains an appreciable number of microorganisms,

27


there is little evidence to indicate that such microbes are harmful if they are left in the cavity under a serviceable restoration. The indirect pulp capping theorized that the layer of residual carious dentin may be “sterilized� or the number of microorganisms can be greatly reduced when this layer is capped with Ca(OH) 2 . The

maintenance

of

pulp

vitality

by

capping

is

preferable to more radical and extensive procedures. Sound clinical judgement should be exercised in the selection of patients for treatment by pulp capping. When a pulp is unlikely to retain a favourable state of health after it has been capped, the tooth should be subjected to pulpotomy or pulpectomy. Pulpotomy The operation of pulpotomy differs from direct pulp capping in the surgical removal of part of the coronal pulp is undertaken. It used to be standard clinical practice to amputate the entire coronal pulp prior to the application of Ca(OH) 2 dressing.

28


This immature

is

the

medicament

permanent

teeth

of choice,

with

the

whenever

incomplete

an root

development (and a reversibly inflamed pulp) suffers a carious exposure or a large diameter mechanical or traumatic pulp exposure. Aseptic technique is employed to prevent irreversible damage

by

introducing

and

establishing

a

bacterial

colonization in the residual pulp. Calcium hydroxide, for covering the amputated pulp may be in the form of a hard setting material, non-setting material or a slurry of freshly mixed powder and saline. Apexogenesis The permanent teeth erupt while they are undergoing tooth formation and root lengthening. As they erupt these incompletely

formed

teeth

are

usually

only

60%-80%

developed with respect to dentin deposition and ultimate root length. Faced with the necessity for RCT and taking into account the unlikely possibility of successful obturation of

29


immature canal systems. It is recommended that these developing teeth be treated with a biologic approach. “Apexogenesis” is defined as physiological root end development and formation. When the vital pulp of a tooth is exposed and two special conditions exist. The pulp not being irreversibly inflamed and special development enclosure being incomplete, the treatment of choice

is

“apical

closure

pulpotomy”

or

apexogenesis

pulpotomy. The goals of apexogenesis pulpotomy are: 1. Sustaining a viable Hertwig’s epithelial root sheath thus allowing continued development of root length for a more favourable crown to root ratio. 2. Maintaining pulp vitality thus allowing the remaining odontoblasts to lay down dentin producing a thicker root and decreasing the change of a root fracture. 3. Promoting root enclosure thus creating a natural special construction for gutta-percha obturation.

30


4. Generating a dentinal bridge at the size site of pulpotomy. Routine Intracanal Dressing Between Appointments a.

Routine Dressing: It is doubtful whether routine dressing (medicaments)

are necessary for RCT in root canals that contain vital pulp tissue as these are not infected prior to instrumentation or in contaminated canals which have been cleaned and shaped with modern instrumentation technique. 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 Ca(OH) 2 which can be placed the full length of the canal is the treatment choice. b.

Long term Temporary dressing When a dressing is placed in a root canal it is usually

removed after a few days and the canal permanently filled with gutta-percha. On occasions, it is necessary for reasons of personal convenience, to leave the dressing in the canal 31


for a considerable period of time. Under these circumstances Ca(OH) 2 may be regarded as the dressing material of choice, because its antimicrobial effect may last for weeks. Periapical Lesions Periapical

granuloma

may

be

formed

by

the

immunological responses of the apical tissues to chronic infection within the root canal. When small they are probably sterile, as they increase in size they may contain an increasing variety of bacteria. In such case it seems reasonable to use a dressing which can be placed as close to the lesion as possible. Calcium hydroxide was used as a root canal dressing in teeth with large periapical lesion and in cases where it was necessary to control the passage of periapical exudates into the canal. Ca(OH) 2

also

accelerated

the

natural

healing

of

periapical lesion, regardless of the bacterial status of the root canal at the time of placement of the material.

32


However,

there

has

been

some

doubt

expressed

concerning the ability of tissues to heal under these circumstances. Ca(OH) 2 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 where by the reduction of seepage occurs is probably due to the fibrous barrier that is formed when Ca(OH) 2 is placed in direct contact

with

host

tissues,

or

to

the

concentration

of

capillaries, or simply to the effect of mechanical blockage. The ability of Ca(OH) 2 to dissolve necrotic tissue is useful as anatomical problems often make it difficult for irrigating solutions to reach all areas of the root canal, in this respect, it has been found that when Ca(OH) 2 dressing was used in addition to irrigation with NaOCl the canal was cleaned as effectively as when ultrasonic instrumentation was used. Treatment of Divergent Apex in a Pulpless Tooth The closure of the apex of a non vital tooth following dressing of root canal with Ca(OH) 2 may occur whether by 33


continued root development if formative elements (Hertwig’s sheath) remain, or by the formation of a calcific barrier of mineralized scar tissue, across the apical foramen. This barrier may be quite deep and is formed by a loose connective tissue inclusion. As a result, the length of the ultimate root filling could be considerably short of the radiographic apex. In both types of closure of the apex, it is invariably found that lateral canals are formed at the junction between the original root and the newly formed tissue. Because Ca(OH) 2 materials are inherently soluble, they must be replaced at 3 months intervals until closure of the apex has occurred, usually upto 6-14 months. Control of Persistent Apical Exudate into the Canal Ca(OH) 2 has been advocated as a routine intracanal dressing, or when exudates persists or there is a long time interval between appointments. There has been progressive bacterial reduction from infected root canals following intracanal application of Ca(OH) 2 . Ca(OH) 2 B.P. can be mixed into a paste with sterile 34


isotonic

saline

or

local

anaesthetic

solution

without

vasoconstrictor and carefully recalled in the canal. Prevention of Root Resorption a. Idiopathic Ca(OH) 2 is frequently used as a dressing for the treatment of both internal and external inflammatory root resorption in order to halt the process and encourage mineralization. It is doubtful whether the material has any real beneficial effect on internal resorption or this is now considered to be sustained by infection within the dentinal tubules coronal to the resorptive process. The

important

aspect

of

treatment

seems

to

be

elimination of the source of infection from the root canal and obturation with gutta percha. b. Following the replacement of an avulsed tooth or transplantation of a tooth Once an avulsed tooth has been splinted in position for about 2 weeks the root canal should be thoroughly cleaned and dressed with Ca(OH) 2 for a period of 3-6 months, prior

35


to the placement of a conventional root filling. Although it has been shown that Ca + 2 and hydroxyl ions do not diffuse through the dentine, the Ca(OH) 2 may still penetrate through lateral canals. The basis of Ca(OH) 2 management of inflammatory root resorption lies on the pH change and neutralization of acids thus preventing mineral dissolution. REPAIR OF IATROGENIC PERFORATIONS Iatrogenic perforation can occur at the elbow of a curved root canal during BMP. A conservative technique to close the perforation with hard tissue induced by Ca(OH) 2 is possible if the defect is below the alveolar crest and is not in communication with the oral cavity. In any event the conservative technique should be investigated immediately after the root is perforated. The timing of the procedure is similar in both cases and success is very much related to the size of the perforation and the evidence

of

extrusion

of

excess

perforation.

36

material

through

the


Martin et al (1982) advocated sealing a mixture of Ca(OH) 2 , barium sulphate and camphorated monochlorphenol in the canal for a few months. Once hard tissue formation had occurred, the mixture was removed with ends of hand instruments, the canal thoroughly irrigated and finally filled with thermoplasticized gutta-percha. It is also important to consider the position of the perforation, necrosis of the periodontal membrane coronal to perforated areas subsequent to the placement of Ca(OH) 2 was reported. They also stressed the importance of an early preliminary dressing of the perforation with Ca(OH) 2 to prevent the ingrowth of granulation tissue. These findings were

attributed

periodontal

to

the

membrane

fact lack

that

fibroblasts

the

capability

from of

the

pulpal

fibroblasts to differentiate into odontoblasts. The

success

rate

for

non-surgical

treatment

of

perforated root canals, which include Ca(OH) 2 dressing was poorest in the cervical region and could be attributed to the close proximity of the epithelial attachment leading to a permanent periodontal defect.

37


The Ca(OH) 2 sealer SEALAPEX was used to treat R.C. perforations. They observed bone healing and ingrowth of trabeculae into the perforation after 42 days. There was also reparative cementum formation and ankylosis. TREATMENT OF ROOT FRACTURES Infraalveolar

root

fractures

occurs

relatively

infrequently, accounting for less than 3% of all dental trauma. The fracture location influences the prognosis and treatment and can be described as coronal, midroot or apical third and the repair was categorized into 4 types: 1. Healing calcification across a narrow fracture line. 2. Healing with intervening fibrous connective tissue. 3. Healing with root end resorption and replacement granulation tissue. When a fracture occurs in the apical third treatment is often

unnecessary,

since

healing

with

calcified

interposed between the fragments in the usual sequelae.

38

tissue


Should

periapical

pathosis

develop

endodontic

treatment upto the coronal segment and surgical removal of the fractured apical portion is usually successful. Ca(OH) 2 also can be used between two segments to induce a calcific barrier before obturating the coronal segment. However this may take several months to occur. CONSTITUENTS OF ROOT CANAL SEALERS Calcium hydroxide based root canal sealers have recently

been

introduced

as

an

alternative

to

the

conventional ZnO eugenol based sealers. Two such materials are sealapex and calcibiotic root canal sealers (CRCS). In the case of the former the setting mechanism is retarded by the replacement of the hydroxide with calcium oxide, compared with lining cement. The rationale for the use of these materials is that if they

are

used

in

canals

with

wide

apical

foramina,

perforation or fractures, mineralized repair may be further induced.

39


When the pattern of release of Ca and hydroxyl ions from different sealers was investigated, it was found that sealapex released ions and disintegrated more rapidly than CRCS. It was also found that, although release of calcium ions from CRCS was negligible the material continued to alkalize its environment possibly due to free eugenol combining with calcium ions as they were released. DENTINE DESENSITIZING AGENT Ca(OH) 2

has

been

advocated

for

the

relief

of

hypersensitive root dentine. The

proposed

mechanism

for

reducing

dentine

permeability include: a. Physical blockage of the tubule orifices. b. Production of precipitates or mineralization. c. Stimulation of secondary dentine. MICROLEAKAGE DETECTOR A relatively novel application for Ca(OH) 2 as a microleakage demonstrator was proposed by Lein Felder et al 1986.

40


This was based on the solubility and OH- release of these cements. ICE water (pH7) was syringed on to Class V cavities in vitro that were filled with amalgam and ionized with Dycal. Subsequent microleakage was detected by placing pH paper over the filling and noting any color change.

They

concluded

that

the

method

was

simple,

biocompatible, quick and could be used in vivo. SUMMARY & CONCLUSION Ca(OH) 2 is a material which has been used for a variety of purposes, since its introduction in dentistry in the early part of 20 t h Century. In its form the substance has a high pH and its dental use relates chiefly to its antibacterial property. The wide use of Ca(OH) 2 in restorative dentistry over many years has generated extensive research. Despite this, the actual mechanisms involved in Ca(OH) 2 induced hard tissue repair remains unclear, which could account for the unpredictable outcome when using this material in different forms. It

would

biocompatibility

seem and

that

investigation

antimicrobial

preparation is still necessary.

41

into

activity

of

chemistry Ca(OH) 2


CALCIUM HYDROXIDE CONTENTS ♦ Introduction ♦ History ♦ Classification and Types ♦ Composition ♦ Physical and Chemical Properties ♦ Mode of Therapeutic action ♦ Applications ♦ Conclusion

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Calcium hydroxide sem/ dental implant courses by Indian dental academy