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1. Intracanal Medicaments
Introduction
The chemicomechanical cleaning of the root canal is the most important
part of the infection control process. Disinfection of the root canal is
accomplished by intracanal medication. Microorganisms present in the canal
can invade the periapical tissue and give rise to pain and destruction of the
periodontium. Bystrom and others have shown by experimental studies that
intracanal medication reduces or eliminates the microbial flora in the root
canal.
History
The historical origins of intracanal medicaments date back to very early
times.
- Seribonius in 1045 AD wrote of using oils and wine in the mouth of
a patient in pain. This was a crude attempt to achieve a topical
anesthetic effect on a tooth to be extracted.
- Dental writings through the Middle Ages indicate the use of oil of
cloves, a plant extract containing a high percentage of eugenol.
- In 1800 specific medicaments were recommended for endodontic
treatment.
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2. - Beechwood creosate was mentioned in 1840 article ‘Creosate and
cotton in Fang filling.’ This medicament is still in common use
today.
- In 1884 Richmond advocated “Knocking out the pulp” by whittling
down orangewood to a small size, soaking the stick in phenol and
tapping this into exposed pulp canal. Phenol was added to preserve
and sterilize the contents of canal and to alleviate pain.
Ideal Requirements
1. It should be an effective germicide and fungicide.
2. It should be non-irritating to the periapical tissues.
3. It should remain stable in solution.
4. It should have prolonged antimicrobial effect
5. It should be active in the presence of blood, serum and protein derivatives
of tissues.
6. It should have low surface tension.
7. It should not interfere with repair of periapical tissues.
8. It should not stain tooth structure
9. It should not induce cell mediated immune response.
10.It should be capable of inactivation in a culture medium.
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3. Categories of use
That is conditions or situations for which intracanal medicaments have
been advocated.
1. Elimination microorganisms: The objective is to sterilize (destroy all viable
microorganisms) or to disinfect (destroy all pathogens) in the canal space.
2. Rendering contents of canal inert: This represents the attempt usually by
chemical means to “mummify”, fix or neutralize tissue or debris left
intentionally or unintentionally in the pulp space.
3. Prevention or control of post treatment pain: The objective is to reduce or
alter the inflammatory response.
4. Enhancing Anesthesia: By reducing the sensitivity of the inflamed, difficult
to anesthetize pulp.
5. Control of persistent periapical abscess : In cases of continually “weeping”
canal or significant pain or swelling medicaments have been suggested as a
means of controlling this difficult situation.
Classifications
According to DCNA
1. Phenolics
- Eugenol
- Camphorated monoparachlorophenol (CMCP)
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4. - Parachlorophenol (PCP)
- Camphorated parachlorophenol (CPC)
- Metacresylacetate (Cresatin)
- Cresol
- Creosote (Beechwood)
- Thymol
2. Aldehydes
- Formocresol
- Glutaraldehyde
3. Halides
- Sodium hypochlorite
- Iodine - Potassium iodide
4. Steroids
5. Calcium hydroxide
6. Antibiotics
7. Combinations
According to Grossman
1. Essential oils - Eugenol
2. Phenolic compound - Phenol
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5. - Para chlorophenol
- Camphorated para chlorophenol
- Formocresol
- Glutaraldehyde
- Cresatin
- N2
3. Halogens - Na hypochlorite
- Iodides
4. Quaternary Ammonium compounds
9 - amino acridine
According to Ingle
He classified antimicrobial agents broadly into 2 groups
Conventional antiseptics / Locally used antiseptics
Chemotherapeutics
Locally used antiseptics: Examples
1. Alcohols - Ethylalcohol
- Isopropyl alcohol
2. Phenolic compounds - Phenol
- Camphorated phenol
- Monochlorophenol
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6. - Paramonochlorophenol
- Thymol
- Eugenol
- Creosote
3. Heavy metal salts - Salts of silver, mercury, copper.
4. Cationic detergents - Quaternary ammonium compounds.
5. Halogens - Na hypochlorite
- Potassium iodide, iodine
Root canal flora
Before considering intracanal medication we shall see what microor-
ganisms we are trying to destroy.
Most commonly found are the gram +ve microorganisms. In some cases
it may be gram -ve microorganisms and few of the cases yeasts. These
organisms are found in various combinations and not as a single species. In
teeth with periapical lesion obligate anaerobes are often found.
Microflora of the root canals also comprise of organisms that can
survive on dead pulp tissue or saprophytes and those that can grow in an
environment of low oxygen tension.
Organisms reaching the root canal have their origin in the mouth.
Although all varieties of microorganisms may have an equal chance of
invading the pulp tissue or the root canal only those best fit for survival in this
environment do survive. The commonest organisms of the mouth, streptococci
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7. are also the most frequently found in root canals. The endodontic problem is
primarily one of eliminating gram +ve organisms because they are the most
abundant, consisting chiefly of streptococci and staphylococci. Among the
streptococci is a small resistant group of enterococci. In addition a small
percentage of gram -ve organisms and yeasts can be isolated from saliva and
from root canals. Recent reports on bacterial flora describe the presence of
obligate and facultative anaerobes.
Factors that predispose teeth to infection:
1. Trauma: The tooth under treatment should be disoccluded if necessary.
2. Devitalized tissue: If present in the root canal or periapical tissue will
interfere with repair or disinfection.
3. Dead spaces : for maximum effect the medicament should be in contact
with the microorganisms in the root canal
4. Accumulation of exudate : Exudate should be allowed to drain or be
removed as it accumulates.
Mode of Action
Conventional antimicrobials attack cells in various ways. When used in
high concentration they have a destructive effect on the bacteria as to cause
denaturation of cell proteins. Antimicrobial agents such as phenols, thymol,
creosate, Eugenol cause coagulation of proteins and subsequently loss of cell
metabolic function may result.
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8. Detergents act as germicides by modifying and damaging the physical
and chemical properties of the bacterial cell membrane.
Iodine, chlorine and heavy metals are strong enzyme inhibitors and
therefore have a destructive effect on microbial cells.
The catalytic effect of enzymes is caused by their affinity to natural
substrate. A competitor is any chemical compound similar to the substrate that
can combine with the active enzyme center but cannot be metabolized.
Through such chemical antagonism the competitor remains attached to the
enzyme and thus prevents it from being active with the natural substrate.
Sulfonamides function as competitor and thus act as antiseptics.
Individual Intracanal Medicaments
Phenol
- Also called carbolic acid
- It is the oldest compound for controlling
microorganisms. It was introduced by Lord Lister in 1867.
- It is white crystalline substance, and has a
characteristic odor derived from coal tar.
- Phenol is a protoplasm poison and produces
necrosis of soft tissues by its ability to penetrate and disrupt the cell
wall of bacteria and subsequently the protoplasm.
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9. - Liquefied phenol consists of 9 parts of phenol
and 1 part water.
- This substance is highly effective in as low
concentration as 1 to 2%
Camphorated phenol
- This contains 30% phenol, 60% camphor, 10% ethyl alcohol
- It is the least toxic of the phenolic compounds
- It has excellent antimicrobial effect and also relieves pain.
- Camphorating process aims at developing a less caustic medicament
as a result of the slow release of phenol. Camphor serves as a vehicle
and diluent.
In clinical use the phenolic compounds are relatively ineffective as
antiseptics.
Monochlorophenol (MCP)
- It is a derivative of phenol and has three isomers of which
paramonochlorophenol is the most effective.
- Mono chlorophenol is more effective antiseptic and is also more
toxic than phenol.
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10. Camphorated paramonochlorophenol (CMPCP) (Developed by
Walkhoff 1891)
- Contains : 35% monochlorophenol
65% camphor
- Its antimicrobial effect is good
- But it is highly toxic to the tissues
- It is used in the form of vapor forming intracanal medicament. The
vapors can pass through the apical foramen.
Formocresol
Developed by BUCKLEY in 1906
- Contents : 19% formaldehyde
35% cresol
46% H2O and glycerine.
or is a combination of formalin and cresol in the proportion of 1:2
- Formocresol combines the protein - coagulating effect of phenolic
compounds with the alkylating effect of formaldehyde.
- The bactericidal effect of formocresol is good at levels as low as 2%.
- It is a strong poison and causes widespread destruction of living
tissue followed by a persistent inflammatory reaction.
- Its vapor forming effect is also good
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11. - Studies have reported that formocresol treated tissue produced a cell
mediated immune response.
Glutaraldehyde
- It is a colorless oil slightly soluble in H2O
- Slightly acidic
- It is a strong disinfectant and fixative
- Used in concentration of 2% as ICM
- Extent of toxicity is less compared to formaldehyde. Its molecular
weight is high compared to formaldehyde hence does not penetrate
into the periapical tissues.
Cresatin
- Also known as metacresylacetate
- It is a clear, stable, oily liquid of low volatility.
- It has both antiseptic and obtundant properties
- Compared to formocresol or camphorated parachlorophenol the
antimicrobial effect of cresatin is less
- Its effect on tissues ranges from mild to severe.
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12. Creosote
- It is a mixture of phenol and phenol derivatives
- Beachwood creosote has long been used in endodontic therapy.
- There are several reports on severe tissue irritation and necrosis
Alcohols
- Ethyl alcohol and Isopropyl alcohol are used
- These denature protiens in high concentration
- Denaturing takes place in presence of water, hence 70% is prefered
to 95%
- They are not recommended as intracanal medicament
Eugenol
- It is the chemical essence of oil of clove
- It is related to phenol
- It is both an antiseptic and an obtundant
- It is slightly more irritating than oil of clove
- Studies have reported that eugenol inhibited intradental nerve
impulses
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13. - A few reports of allergy to eugenol have been reported.
Heavy metal salts
- Salts of silver, copper and mercury are used as ICM.
- They coagulate protiens and act as enzyme inhibitors.
- They are toxic.
- The mercury salts are rendered less effective by the tissue fluid
proteins present in the root canal. Hence they are not often used.
N2
Contains : Paraformaldehyde
Phenylmercuric borate
Eugenol. Additional ingredients like lead, corticosteroids,
antibiotics.
- It is claimed to be both ICM and a sealer
- Claims that N2 has a permanent disinfectant action and unusual
antimicrobial properties have been denied by the council on Dental
Therapeutics of the American Dental Association.
- The antibacterial effect of N2 is short lived about a week to 10 days.
Halogens :
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14. Includes chlorine and iodine containing compounds Sodium
hypochlorite
- Hypochlorite was first used by Semmelweis in 1847 as a hand
disinfectant
- This initial use of potassium hypochlorite was substituted by sodium
hypochlorite by carrel and Dakin for wound disinfection
- Mechanism of action : When hypochlorite contacts tissue proteins,
nitrogen, formaldehyde and acetaldehyde are formed. The peptide
links are broken up and this dissolves the proteins. During the
process hydrogen in the amino groups (-HN-) is replaced by chlorine
(-NCl-) there by forming chloriamine, which plays an important role
in antimicrobial effectiveness. Thus necrotic tissue and pus are
dissolved and the antimicrobial agent can better reach and clean the
infected areas.
- Temperature increase significantly improves the antimicrobial effect
of sodium hypochlorite
- Dakin suggested a 0.5% solution (Dakin’s Solution) At this
concentration toxicity is low and it affects only necrotic tissue.
- A 1% sodium hypochlorite solution however is more potent and
provides an increased antimicrobial effect
- Higher concentrations of NaOCl (2.5% and 5%) attack living tissue
without contributing significantly to treatment (i.e ↑ in antibiotic
activity)
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15. - Bystrom and Sundqvist have demonstrated that the rate of root canal
disinfection was similar regardless of whether 0.5% or 5%
concentration of NaOCl was used
- The activity of NaOCl is intense but of short duration. Hence the
compound should preferably be applied to the root canal every other
day.
Iodides :
- Iodine has been used for many years and is known for its mild effect
on living tissue.
- Iodine is highly reactive, combining with proteins in a loosely bound
manner so its penetration is not impeded.
- Iodine potassium iodide which contains 2% I2, 4% KI and 94%
distilled water has excellent antimicrobial activity and minimal
toxicity and tissue irritating qualities.
Cationic detergents
- The quaternary ammonium compounds have low surface tension and
good cleansing effect.
- The antimicrobial effect of these compounds are not strong.
- Mechanism of action is as follows, the ‘Quats’ are positevely
charged and the microorganisms are negatively charged. Thus a
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16. surface active effect results in which the compound clings to the
microorganism and reverses the charge.
- These compounds may delay wound healing
- These compounds are used in the concentrations between 0.1 to 1%
for root canal irrigation, but rarely as intracanal dressings
- Salvizol is also a detergent suggested for irrigation during root canal
instrumentation
- It has chelating effect
- Salvizol causes some degree of tissue irritation
Calcium hydroxide
- Hermann introduced Ca(OH)2 paste as an ICM in 1920
- Calcium hydroxide paste for intracanal use is a thick suspension of
Ca(OH)2 powder in sterile water or saline.
- The high pH of calcium hydroxide paste is responsible for the
destructive effect on bacterial cell membranes and protein structures.
Few bacteria can survive at this pH of approximately 12.5
- In addition to its antimicrobial qualities the paste may also aid
directly or indirectly in the dissolution of necrotic pulp tissue. Tissue
submerged in Ca(OH)2 for a day is more easily dissolved with
NaOCl than is untreated tissue.
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17. - Bystrom et al showed that Ca(OH)2 paste effectively eliminated all
microorganisms in infected root canals when the dressing was
maintained for 4 weeks.
- Mode of application : The paste is introduced into the root canal with
a lentulo spiral, dried with coarse absorbent points and packed with
appropriately sized root canal pluggers. Temporary cement is then
placed for an effective seal.
Antibiotics
- Alone and in combination with other drugs, antibiotics have been
used as intracanal medicament
- Antibiotics are indicated in a small minority of cases when root canal
infection persists despite other antiseptics
- Ladermix paste or polyantibiotic paste (PBSC) are used
Ledermix paste
Contains : 1% triamcinelone acetonide
Glucocerticosteroid
3% dimethl chlortetracycline
PBSC paste
Contains : Potassium penicillin G (10,00,000 units)
Bacitracin (10,000 units)
Streptomycin paste (1gm)
Sodium caprylate / Nystatin (1gm)
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18. Steroids
A wide variety of steroid molecules have been synthesized, a few of
these have been utilized as intracanal medicaments. The steroid used is 0.1%
triameinolone which is commercially available in a water base vehicle.
Frequency of medication
According to the general principles of root canal management,
disinfectant dressings should preferably be renewed in a week and not longer
than 2 weeks because dressings become diluted by periapical exudate and are
decomposed by interaction with the microorganisms.
The mode of application traditionally was a short blunt absorbent point
moistened with the medicament is placed inot the canal, a cotton pledget from
which excess medicament has been expressed is placed in the pulp chamber
and the access cavity is sealed. In narrow canals a dry absorbent point is
inserted and a cotton pledget moistened with the medicament is placed against
the absorbent point to moisten it. A dry cotton pledget is used to absorb the
excess medicament and the cavity is sealed.
However many endodontists prefer to place a medicated cotton pellet in
the chamber from which excess medicament has been removed. They depend
on the vaporization of the medicament in the pulp chamber for antibacterial
action. They do not place an absorbent point in the root canal. The canal is then
sealed with a temporary restorative material.
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19. Antimicrobial Effectiveness
The effectiveness of antimicrobials depends upon the direct contact of
the agent with the virus, bacteria or fungus and in sufficient concentration.
There is a serious drawback to the use of a chemical substance in a pulp space,
that substance probably does not reach all areas where bacteria are sequestered.
Another significant concern is the duration of effectiveness of the
medicaments in the pulp space. Recent research has shown that the
antibacterial potency of phenolics drops off very quickly and becomes
ineffective.
Also of concern is toxicity. Anything that kills microbes also may
destroy or depress host cells. Numerous in vitro and in vivo studies have
examined these toxicity factors.
Invitro Studies
Under laboratory test conditions the ICM were highly effective in
destroying or inhibiting the growth of microorganisms. Some of the
medicaments accomplish this even in very low concentrations.
To test the toxicity of medicaments the invitro study involves the use of
cell cultures to determine the potency of the medicaments. It the medicament
showed comparable cell destruction as they did toward bacterial destruction
they were classified as toxic.
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20. If the results of the invitro tests were applied directly, the medicament of
choice would be iodine-potassium iodide. This demonstrates relatively high
antibacterial activity and relatively low toxicity. It has been suggested that
sodium hypochlorite irrigant be utilized as an inter appointment medicament,
leaving the canals flooded rather than dry.
In Vivo studies
This is done by intracanal sampling and culture techniques to test for the
presence of bacteria. However this test is not precise and does not reflect the
true status of the canal. Viable bacteria may remain untouched by the
medicament and still not be recovered by bacterial sampling techniques.
Important to note here is that phenolic type of ICM (CMCP and PCP) quickly
lose their antimicrobial action when sealed in the pulp space, remaining
bacteria would then proliferate and repopulate.
Many antimicrobial agents become more effective at higher temper-
atures. Warming solutions to approximately 140o
F (60o
C) significantly
enhances the antimicrobial activity in vitro of these solutions.
Complications and side effects
Substances applied to the pulp have ready accessibility to the periapical
tissues and to the systemic circulation. Thus pharmacologically active
chemicals which includes all medicaments must be used with caution.
Phenolic derivaties and aldehydes
These chemicals possess a pungent, obnoxious odour and foul taste.
They also cause marked destruction of tissue. They will kill cells on contact
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21. and have been shown to delay healing. Another adverse side effect is their
potential allergenicity. Investigations have shown that some medicaments may
act as a hapten and alter tissues to the extent that they may become foreign
substances to the body. An immune response to these altered tissues may result
in inflammation and additional tissue destruction.
Halides
This group of chemicals have less irritating and destructive capabilities
but they tend to destroy cells on contact. Iodine can elicit allergic response.
Antibiotics
In some cases, intracanal penicillin elicited a systemic allergic response
in previously sensitized patients. This same effect has not been shown with
other antibiotics.
Steroids
The use of these powerful drugs has side effects like delay of healing,
inhibition of body defenses and immune response permitting bacterial
proliferation and suppression of adrenal activity. However these occur with
repeated administration or with long term steroid therapy. Single does, even
when large are considered to be quite safe in the healthy patients. According to
Richard Walton steroids are effective in preventing pain and show promise as
pain relieving agent. This drug, whether applied topically or administered
systemically is a potent anti-inflammatory agent, true particularly when given
in large single doses. Pain, the byproduct of inflammation is therefore sup-
pressed.
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22. Conclusion
Intracanal medicaments in endodontics have been used for the reduction
in the number of microorganisms, rendering canal content inert, prevention of
post treatment pain and to enhance anesthesia. Research has shown the toxicity
and potential allergenicity of the commonly used ICM particularly those of
phenolic and aldehyde derivatives.
With a wide choice of ICM now available selection should be made
according to the special needs of the case in question.
NaOCl remains the most popular ICM although the recommended
strength varies from 0.25 to 5%. The safest ICM however is I2-KI solution.
According to Richard walton intracanal medicaments are primarily useless. The
one exception is intracanal or systemic steroids. They are effective in reducing
the incidence of post treatment pain.
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