Normal Saline Infusion: Uses and Side Effects

Normal Saline

Normal saline at 0.9% w/v is commonly used in endodontics for gross debridement and lubrication of root canals because it acts by fishing action. Since it is very mild in action, it can be used as an adjunct to chemical irritants. It can also be used as a final rinse for root canals to remove any chemical irritant left after root canal preparation.

Normal Saline Advantages:

It is biocompatible in nature. No adverse reaction even if extruded periapical because the osmotic pressure of normal saline is the same as
that of the blood.

Read And Learn More: Endodontics Notes

Normal Saline Disadvantages:

• Does not possess dissolution and disinfecting properties
• Too mild to thoroughly clean the canals
• Cannot clear microbial flra from inaccessible areas like accessory canal
• Does not possess antimicrobial activity
• Does not remove the smear layer

Sodium Hypochlorite

Sodium hypochlorite is a clear, pale, green-yellow liquid with a strong odor of chlorine. It was introduced during World War I by chemist Henry Drysdale Dakin for treating infected wounds. It is known as Dakin’s solution.

The original concentration suggested by Dakin was 0.5%. Besides being a wide spectrum, it is sporicidal, has tissue-dissolving properties. Due to these properties, Coolidge suggested the use of hypochlorite as an endodontic irrigant in 1919.

Availability:

• Unbuffered at pH 11 at conc. 0.5% to 5%
• Buffered with bicarbonate at pH 9.0 as 0.5% or 1% solution

Mechanism of Action of Sodium Hypochlorite:

• At body temperature, reactive chlorine in an aqueous solution exists in two forms—hypochlorous acid (HOCl) and hypochlorite (OCl) depending on the pH of the solution. On coming in contact with organic tissues:
• It forms glycerol and fatty acid salts (saponification reaction), resulting in the surface tension of the solution.
• It causes an amino acid neutralization reaction resulting in the formation of salt and water. pH decreases due to the release of hydroxyl ions.
• When hypochlorous acid comes in contact with organic tissue, it releases chlorine which combines with amino acids forming chloramines. This chlorination reaction between chlorine and amino acids causes interference in cell metabolism.

Together these three reactions that occur in the presence of organic tissues lead to tissue dissolution and an antibacterial effect.

Methods to Increase the Efficy of Sodium Hypochlorite:

Time:

The antimicrobial effectiveness of sodium hypochlorite is directly related to its contact time with the canal.

Heat:

An increase in temperature by 25°C enhances efficacy by a factor of 100. But one should be careful not to overheat the solution because this can cause the breakdown of sodium hypochlorite constituents and thus may damage the solution.

pH:

If NaOCl is diluted, its tissue dissolving property decreases. In an aqueous solution, hypochlorous acid dissociates into hypochlorite:

HOCl ↔ H⁺ + OCl^–

HOCl is a stronger oxidant than hypochlorite ion, i.e. HOCl is responsible for strong chlorination, oxidizing action, and tissue dissolution. The dissociation of HOCl to OCl depends on pH. At pH 10, the OCl form exists and at pH of 4.5, the HOCl form dominates. So, the antibacterial properties of hypochlorite are more in acidic pH.

Ultrasonic Activation of Sodium Hypochlorite:

Ultrasonic activation of sodium hypochlorite has been shown to accelerate the chemical reactions, create a cavitational effect and thus achieve a superior cleansing action.

Precautions to be Taken while Using Sodium Hypochlorite Solution:

It is important to remember that though sodium hypochlo- rite is nontoxic during intracanal use but 5.25% NaOCl can cause serious damage to tissue if injected periodically. If sodium hypochlorite gets extruded into periapical tissues, it causes excruciating pain, periapical bleeding, and swelling.

As the potential for the spread of infection is related to tissue destruction, medication like antibiotics, analgesics, and anti-histamine should be prescribed accordingly. In addition to these, reassurance to the patient is the prime consideration. Therefore, to avoid accidental extrusion of hypochlorite, care should be taken to do passive irrigation, especially in cases with large apical openings.

Precautions to be Taken while Using Sodium Hypochlorite Solution Advantages:

• Causes tissue dissolution
• Remove an organic portion of dentin for deeper penetration of medicament
• Removes biofilm
• Causes dissolution of pulp and necrotic tissue
• Shows antibacterial and bleaching action
• Causes lubrication of canals
• Economical
• Easily available

Precautions to be Taken while Using Sodium Hypochlorite Solution Disadvantages:

• Because of high surface tension, its ability to wet dentin is less
• Irritant to tissues, if extruded periodically, it can cause tissue
  damage
• If comes in contact, it causes inflammation of the gingiva because of its caustic nature
• It can bleach the clothes, if spillage occurs
• It has a bad odor and taste
• Vapors of sodium hypochlorite can irritate the eyes
• It can be corrosive to instruments
• It is unable to remove inorganic components of the smear layer
• Long time of contact with dentin has determined the effect on flexural strength of dentin
• Exudate and microbial biomass inactivate NaOCl. So, continuous irrigation and time are important when irrigation is done with NaOCl

Hydrogen Peroxide

It is a clear, odorless liquid and mainly a 3% solution of hydrogen peroxide is used as an irrigating agent.

Mechanism of Action:

• It is highly unstable and easily decomposed by heat and light. It rapidly dissociates into H₂O + [O] (water and nas- cent oxygen). On coming in contact with tissue enzymes catalase and peroxidase, the liberated [O] produces bac- viricidal effect but this effect is transient and diminishes in the presence of organic debris
• It causes oxidation of the bacterial sulfhydryl group of enzymes and thus interferes with bacterial metabolism
• Rapid release of [O] on contact with organic tissue results in effervescence or bubbling action which is thought to aid in mechanical debridement by dislodging particles of necrotic tissue and dentinal debris and floating them to the surface

Hydrogen Peroxide Uses:

It is used as an irrigating solution either alone or alternatively with sodium hypochlorite. The advantage of using alternating solutions of 3% H2O2 and 5.2% NaOCl are

• The effervescent reaction by hydrogen peroxide bubbles pushes debris mechanically out of the root canal
• The solvent action of sodium hypochlorite on organic debris
• Disinfecting and bleaching action by both solutions

Hydrogen Peroxide Clinical Tips:

While using a combination of sodium hypochlorite and hydrogen peroxide, always use sodium hypochlorite in the last because hydrogen peroxide can react with pulp debris and blood to produce gas (nascent oxygen) which builds up pressure on closing the tooth, this can result in severe pain.

Urea

It is a white, odorless, crystalline powder. It was used in World War I as a therapeutic agent for infected wounds. Urea solution (40% by weight) is a mild solvent of necrotic tissue and pus and is a mild antiseptic too. In 1951, Blechman and Cohen suggested that 30% urea solution can be used as a root canal irrigant in patients with vital pulp as well as those with necrotic pulp.

Mechanism of Action:

• Denaturation of protein: Urea denatures the protein by destroying bonds of the secondary structure resulting in the loss of functional activity of the protein. This mode of action is responsible for its antiseptic property
• It has the property of chemically debriding the wound by softening the underlying substrate of firing

Urea Uses:

• It is an excellent vehicle for antimicrobials such as sulfonamides
• It has low toxicity
• It can be used in teeth with open apices or areas with resorptive defects

Urea Peroxide

It is a white crystalline powder with a slight odor. It is soluble in water, alcohol, and glycerine.

Mechanism of Action:

• It decomposes rapidly when exposed to heat, light, or moisture. It dissociates into urea and hydrogen peroxide
• Urea peroxide → Urea + H₂O₂
• Its mechanism of action combines the effects of urea and hydrogen peroxide.

• Anhydrous glycerol increases the stability of urea peroxide

Urea Peroxide Uses:

• A 10% solution of urea peroxide in an anhydrous glycerol base is available as a glycoside. The advantages of adding glycerol are
  • It increases the stability of the solution, thus increasing shelf life
  • It acts as a good lubricant, so facilitates the negotiation and instrumentation of thin, tortuous root canals
  • Glyoxide can be used along with EDTA- Ethylenediaminetetraacetic acid to clean the walls of the canal

Urea Peroxide Disadvantages:

It dissociates more slowly than hydrogen peroxide (H₂O₂). So, its effervescence is prolonged but not pronounced. This can be overcome by alternating irrigation with sodium hypochlorite.

Chlorhexidine

Chlorhexidine (CHX) is the most potent of tested bisbi- guanides. It has a strong base and is most stable in the form of its salts, that is, chlorhexidine gluconate. It shows optimal antimicrobial action between pH 5.5 and 7.0. For canal irrigation, it is used in 2% concentration.

Mechanisms of Action:

• Chlorhexidine is a broad-spectrum antimicrobial agent which is due to its cationic bisbiguanide molecular structure
• The cationic molecule is absorbed to negatively charged phosphate groups of the microbial cell walls. This alters the cell’s osmotic equilibrium and causes leakage of intracellular components
• At low concentrations, it acts as a bacteriostatic, whereas at higher concentrations, it causes coagulation and pre- precipitation of cytoplasm and therefore acts as bactericidal
• Chlorhexidine has the property of substantivity (residual effect). It can show residual antimicrobial activity for 72 h or even up to 7 days if used as an endodontic irrigant

Chlorhexidine Disadvantages:

• It is unable to dissolve necrotic tissue remnants
• It is less effective on Gram-negative than on Gram-positive bacteria
• Does not show the effect on biofilms

A combination of NaOCl and CHX is preferred to enhance their antimicrobial properties. However, the presence of NaOCl in the canals during irrigation with CHX produces an orange–brown precipitate known as parachloroaniline (PCA). This precipitate occludes the dentinal tubules and may compromise the seal of the obturated root canal.

Moreover, leaching of PCA from the insoluble precipitate has shown to be cytotoxic in rats and carcinogenic in humans. Formation of the precipitate can be prevented by minimizing the chance for two irrigants to come in contact with each other. Basrani et al. advocated fishing of remaining NaOCl with alcohol or EDTA, before using CHX.

Chelating Agents

A chelating agent is defined as a chemical which combines with a metal to form a chelate. Chelating agents were introduced in dentistry in 1957 to aid in the preparation of narrow and tortuous canals to soften the canal dentin, increase dentin permeability and remove the smear layer.

EDTA:

Ethylenediaminetetraacetic acid (EDTA) is the most commonly used chelating agent. It was introduced in dentistry Mechanism of action of chlorhexidine. by Nygaard-Ostby for cleaning and shaping of the canals. It contains four acetic acid groups attached to ethylene-amine. EDTA is relatively nontoxic and slightly irritating in weak solutions. The effect of EDTA on dentin depends on its concentration and duration of contact with dentin.

Chelating Agents Clinical Tips:

EDTA and citric acid are used for 2–3 min at the end of instrumentation to remove the smear layer so as to improve the antibacterial effect of locally used disinfecting agents in the deeper layer of dentin

EDTA or citric acid should never be mixed with sodium hypochlorite because EDTA and citric acid strongly interact with sodium hypochlorite. This immediately reduces the available chlorine in the solution and thus making it ineffective against bacteria

Functions of EDTA:

• Lubrication
• Emulsification
• Holding debris in suspension
• Smear layer removal

Mechanism of Action:

• It inhibits the growth of bacteria and ultimately destroys them by starvation because EDTA chelates with the metallic ions in a medium which are needed for the growth of microorganisms
• EDTA has self-limiting action. It forms a stable bond with calcium and dissolves dentin, but when all chelating ions are reacted, an equilibrium is reached which prevents further dissolution. According to Goldberg and Speilberg, the demineralization effect of EDTA is more at neutral pH than at alkaline pH.
• EDTA removes the smear layer within 1 minute of exposure and this effect doubles after 15 minutes of exposure. Further, an increase in time of contact does not increase the demineralization effect. This may be because of chelating material which starts to affect the dentin surface causing slower phosphorus release. This suggests refreshing the EDTA solution after 15 minutes.
• Calt and Serper found that increasing the contact time along with concentration from 10% to 17% and pH 7.5 to 9.0 has been shown to increase dentin demineralization.

Uses of EDTA:

• It has dentin-dissolving properties
• It helps in enlarging narrow canals
• Makes easier manipulation of instruments
• Reduces the time needed for debridement

Diffrent Preparations of EDTA:

• Liquid type:
  • REDTA: In this, 17% EDTA is combined with cetrimide, that is, cetyltrimethylammonium bromide to reduce the surface tension.
  • EDTAT: EDTA is combined with sodium lauryl ether sulfate (Tegretol) which reduces the surface tension.
  • EDTAC: It is commercially available as a 15% solution with and pH of 7.3 under the name EDTAC because it contains catalog, a quaternary ammonium compound which is added due to its disinfecting properties. It reduces the contact angle of EDTA when placed on a dentin surface and thus enhances its cleaning efficacy.
  • Largal Ultra: It contains 15% EDTA solution as a disodium salt, cetrimide, and sodium hydroxide to adjust pH value to 7.4.

• Paste type:
  • Calcinase slide: It contains 15% sodium EDTA and 58%–64% water but no peroxides or preservatives. It has stable pH of 8–9. This gel is thixotropic in nature, so it is firm at room temperature and forms a creamy consistency when agitated. So it sticks to the instrument very well and spreads well in the root canal.
  • RC prep: It consists of 10% urea peroxide, 15% EDTA and glycol in an ointment base. The presence of glycol makes it a lubricant and coats the instrument which facilitates its movement in the canal.
  • Glyde fie: It consists of 10% urea peroxide, 15% EDTA in an aqueous solution. In reaction with NaOCl, oxygen is released from urea peroxide which causes effervescence. This facilitates the removal of pulpal remnants and debris.
  • File-Eze: It contains 19% EDTA in an aqueous water-soluble solution.

Diffrent Preparations of EDTA Clinical Tips:

Collagen is a major constituent of vital pulp which can be packed into a glue-like mass which contributes to iatrogenic blocks. Without the use of a chelator, vital tissue tends to collapse and adheres to itself, but the use of a chelator does not allow this phenomenon to occur and accelerates the emulsification of tissue

Citric Acid:

• The use of 10% citric acid has been shown to remove the smear layer. It reacts with metals to form non-ionic chelate. It shows antimicrobial activity against facultative and obligative anaerobes
• Citric acid should not be used with sodium hypochlorite as it interacts with NaOCl and reduces the available chlorine making it ineffective against microorganisms

Polyacrylic Acid;

It is commercially available as Durelon and Fuji II liquid. Polyacrylic acid and 7% malic acid may be used to remove the smear layer.

Hydroxyethylidene Bisphosphonate:

• It is also known as etidronate or etidronic acid
• Hydroxyethylidene bisphosphonate (HEBP) is a nontoxic chelating agent and shows only short-term interference with sodium hypochlorite.

Maleic Acid:

It is a mild organic acid used as a conditioner in adhesive dentistry.

Salvizol:

• It belongs to surface-acting materials like the quaternary ammonium group. It shows antibacterial properties even in the presence of organic materials
• It is most effective against Gram-positive and Gram-negative microorganisms and fungi

Tetraclean:

It is a mixture of doxycycline hyclate [lower concentration than a mixture of a tetracycline isomer, an acid, and a detergent (MTAD)], an acid, and a detergent. It has been shown to remove microorganisms and smear layers from dentinal tubules with a fial 5-min rinse.

Chlorine Dioxide:

Chlorine dioxide is similar to hypochlorite and studies have shown that ClO 2 is equally efficient to NaOCl for dissolving organic tissue. Since, ClO2produces little or no trihalomethane- anes (carcinogen), it might prove as better dental irrigant than NaOCl.