INTRODUCTION An important objective in endodontic therapy is the removal of pulpal and dentinal debris from the root canal system, to accomplish this it is essential to use an irrigant or combination of irrigants during and after biomechanical preparation of the canal system. Refers to as chemical preparation, when accomplished simultaneously are often reported as “chemomechanical preparation”. GOALS OF IRRIGATION Four goals of irrigation : 1. Lavage of debris 2. Tissue dissolution. 3. Antibacterial action and 4. Lubrication. Debridement with hand instruments alone are not possible able to remove all the tissue remnants in the pulp chamber and canals. It is necessary to rely on some means of chemical dissolution of the remaining tissue, and this depend upon the type of remaining tissue whether it is vital, necrotics, or chemically fixed tissue, unfortunately, irrigants are not equally effective on all three tissue types. Some tissue all three tissues may be encountered clinically in the same tooth. Other variables are the method and extent of canal instrumentation – whether coronal apical or apico coronal (step back), preparation.
Laboratory studies have shown, for example, that the step-back preparation leaves less tissue debris. â€˘ The extent of instrumentation and the size of the last instrument used at working length influence the penetration of irrigants. â€˘ Quantity and temperature of the irrigating solutions the length of time of contact, the level of observations (apical, middle, or coronal), the presence of serum proteins, the depth of penetration of the irrigating needle, the type and gauge of the irrigating needle, the surface tension of the irrigating solution (with alcohol or detergent), and the age of the solution are all influences the effects of the irrigating solutions.
DESIRABLE PROPERTIES FOR AN ENDODONTIC IRRIGANT The chemical agent selected for endodontic irrigation should poses from major properties : 1. Should have antimicrobial activity. 2. Dissolve necrotis tissue. 3. Aid in debridement of the canal system. 4. Be nontoxic to the periradicular tissues. The first three of these properties are interrelated, tissue dissolution property aids in the debridement by dissolving organic debris, these assist in reducing the microbial flora by removing necrotic debris and thereby reducing the substrate that promotes the growth of microorganisms.
HISTORY OF IRRIGATING SOLUTIONS Prior to 1940, water was the most commonly used endodontic irrigant, it provided lubricating effect making instrumentation of the canal wall easier. The number and types of irrigants that have been recommended later on include acid, chelating agents, proteolytic enzymes, alkaline solutions and other clinical agents such as oxidizing agents and normal saline solutions. ACIDS AND CHELATING AGENTS Acids and chelating agents were used because of their ability to soften dentin, making enlargement of the canal system easier. Acids such as 30% hydrochloric acid and 50% phosphoric acid were used as late as 1940s with little or no understanding of effects on periradicular tissues. These caustic acids dissolved inorganic structure of dentin with the remaining organic matrix offering less resistance to instrumentation. Chelating agents - came into increasing use in the 1970s. They softened the dentin better then acids and also far more biologically acceptable to the soft tissues. They combine with and inactivate calcium ions. This decalcification effect results in less resistance to instrumentation. CHELATING AGENTS ARE: EDTA, REDTA (EDTA buffered with sodium hydroxide in an aqueous vehicle). RC-Preparation (EDTA and urea peroxide) and citric acid.
Proteolytic Enzymes Were utilized in 1930s and 1940s for their tissue solvency effect. They possessed very little tissue solvency property within root canal systems. Enzymes used in the therapy are : Streptokinase, streptodornase, papain, enzymol and purified trypsin.
Alkaline Solutions Used solutions are, sodium dioxide, sodium hypochlorite, potassium hydroxide, urea and sodium hypochlorite. Sodium hypochlorite has been proved clinically acceptable and is the most commonly used irrigant in endodontics. Oxidizing Agents In 1943, Grossman introduced the concept of using an oxidizing agent as an irrigant in conjunction with sodium hypochlorite. He recommended that solution of 3% hydrogen peroxide be alternated with a solution of 5.25% sodium hypochlorite, so that the foaming action resulting from the chemical reaction would help to remove debris from the canal system. Recently another oxidizing agent, gly-oxide has been recommended, particularly for narrow, curved canals contains carbamide peroxide in an anhydrous glyceral base is highly viscous, glyceral base provides very good lubrication, has little antibacterial activity not a tissue solvent.
Sodium Hypochlorite Used as an endodontic irrigant for well over four decades. It is reducing agent, is a clean straw colored solution containing about 5% of available chlorine. This irrigant when used during cleaning and shaping act as a lubricant, solvent of the pulp tissue, antiseptic and bleach. The amount of dilution and its use in combination with other irrigants such as glyoxide, RC-Prep, or hydrogen peroxide still remain controversial. Trepagnier has reported either 5.25% or 2.6% sodium hypochlorite has the same effects for a period of 5 minutes when used in root canal system. Cunningham has shown 5.26% and 2.6% NaOcl were equally effective at 37째C (body temperature) warming the solution increase its antibacterial effect. Rosefield demonstrated 5.25% sodium hypochlorite dissolves vital tissue and dissolves necrotic tissue better than in any other concentration. Antimicrobial property is due to the destruction of bacterial by penetration into the bacterial cell and chemical combination with the protoplasm of the bacterial cell.
Hand and associates have shown that sodium hypochlorite retain its antimicrobial activity in the presence of organic matter such as blood and serum albumin. Alternate irrigation with sodium hypochlorite and hydrogen peroxide (3%) produces energetic effervescence that mechanically forces debris and microorganisms out of the canal. Release of nascent oxygen causes the forming effect. -
Combination seems to reduce the tissue solving property advantage is mechanically bubbles and pushes the debris.
The solvent action of the sodium hypochlorite.
The disinfectant and, bleaching action by both solution. Sodium hypochlorite should be used last because hydrogen peroxide can
react with pulp debris and blood to form gas, trapped gas in the tooth causes continuous pain. Fischer and Huerta believe it is the alkaline property (pH 11.0 â€“ 11.5) of sodium hypochlorite that makes it effective against anaerobic microbes. Bactericidal effect gained by combining sodium hypochlorite with other chemicals come from the release of chlorine gas. It is true with citric acid, some extent with EDTA and not with hydrogen peroxide. Sodium hypochlorite is a tissue irritant and this discourages its use to its full strength.
CHELATING AGENTS Most common chelating solutions used for irrigation Tublicid, EDTA, EDTAC, File-Eze and RC-Prep. In all of these EDTA-Ethyline diamine tetraacetic acid is the active ingradient. Introduced into the endodontic practice by Nygaard Ostby. Later he introduced EDTAC, EDTA with cetrimide, quaternary ammonium compound to reduce surface tension and increase penetration, cetrimide acts as disinfectant. EDTA functions by forming a calcium chelate solution with the calcium ion of dentin : (the dentin becomes more fliable and easier to instrument). When all of the available inorganic matter of dentin is chelated by the EDTADentin reaction, a chemical equilibrium is established. EDTA
This equilibrium reaches within 7 hours, regardless of surface area involved indicating that EDTA is chemically self limiting in the chelation of irorganic material from dentin. The optimal pH for the demineralizing efficiency of EDTA as shown by Valdrighi is between 5.0 and 6.0.
Goldberg has shown EDTAC increases permeability into dentinal tubules accessory canals and apical foramina. McComb found EDTA sealed in the canal for 24 hrs produced the cleanest dentinal walls. Goldman and colleagues in 1981 were shown combined use of sodium hypochlorite and EDTA removed smear layer, chelating agents remove only calcified tissues whereas sodium hypochlorite removes organic material confirming the composition of smear layer. Original Nygaard Ostby formula for 15% EDTA was -
Disodium salt of EDTA 17.0g
Distilled water 100.00ml
5ml sodium hydroxide 9.25 ml
Summarizing the effects of EDTA studied by both in vitro and invivo. 1. Effective in softening the dentin. 2. Has distinct antimicrobial properties. 3. Is capable of causing moderate degree of irritation. 4. Has no deliterious effect when used clinically. 5. Irrigation with EDTA removes smear layer. 6. Demineralization is proportional to the exposure time. 7. To a depth of 20-30Âľ in 5 minutes. In 1969 Stewart and others developed RC-prep. is composed of EDTA and urea peroxide in a base of carbowax. An effectiev lubricating and cleaning agent for root canals and allowed deeper penetration of the medicament into the dentin.
According to Cook and associates RC-preparation allowed maximum leakage into filled canals over 2-6 times the leakage of the canals. Another root canal irrigant is solvizol which is N 1-N1-Decamethylene – N4, N4-decamethylenebis – 4 – amino quinaldinium–diacetate Kaufman suggested that with a neutral pH has a broad spectrum of bactericidal activity as well as the ability to chelate calcium, makes it a cleansing potency and biologically compatible. This applies to tublicid (green, red and blue) as well. EDTA is inserted by depositing a few drops in the pulp chamber with a syringe and then carefully pumping the solution into the root canal with a fine root canal instrument, and is continued with the solution bathing the canal at all times until cleaning and shaping are completed.
ORGANIC ACIDS Tidmarch, felt 50% citric acid gave the cleanest dentin walls without a smear layer. Wayman reported excellent filling results after preparation with citric acid (20%), followed by 2.6% sodium hypochlorite and a final flushing with 10% citric acid US Air Force tested effective as a bactericidal in 5-10min. other organic acid used to remove smear layer are polyacrylic acid for one as Durelon and Fuji II liquids, both 40% polyacrylic acids.
OTHER IRRIGANTS 9-amine acridine reviewed by Schmitz enjoys regional popularity because of its low toxicity and antimicrobial action and has a purported “osteogenic potential”, has no wide spread use because its not a tissue solvent or chelator. Chloriamine – T has little ability to dissolve necrotic tissue. -
Chlorhexidine gluconate (0.2%). Recently, Loma Linda group reported it to be more effective as an antimicrobial agent.
Kaufman reported bis-dequalinium acetate (BDA) as disinfectant and chemotherapeutic agent. He cites its low toxicity, lubrication action, disinfecting ability, and low surface tension, as well as its chelating properties and low incidence of post-treatment pain. It is marked as solvidont. BDA is recommended as an excellent substitute for sodium hypochlorite
in those who are allergic to sodium hypochlorite. Action of chlorhexidine : action is the result of absorption of chlorhexidine onto the cell wall of the microbes thereby altering the cells osmotic equilibrium; resulting in leakage of intracellular components. Broad spectrum, antimicrobial, substantivity and relative absence of toxicity.
2% glutaraldehyde - Wemes and co-workers 1982 used 2% glutaraldehyde as an endodontic irrigant. It causes irreversible fixation of tissues, they observed smooth layer of dentin material resulted in closure of apical and lateral canals and the dentinal tubules and showed considerable antibacterial effect.
ULTRASONIC IRRIGATION The use of ultrasonic irrigation to better cleanse root canals, of their fillings debris and bacteria has been well reported by Martin and Cunningham. The oscillating movement of the file creates ultrasonic wave of sodium hypochlorite irrigant solution which is delivered along the side of the file and the vibration produces heat that increases the chemical effectiveness. It also produces cavitation, that is the growth and collapse of bubbles, with a resulting increase in the mechanical cleansing activity of the solution, this increases in thermal and mechanical activity of the solution, helps in removal of debris and tissue from the isthmus and removal of smear layer are more efficient bactericidal action also increases. Sonic system uses water as an irrigant and doesnâ€™t usually require diamond files for the flare of the preparation.
Technique The instrument required is a disposable plastic or glass syringe with an endodontic notched needle. The needle should be bent to an angle to reach the canals of posterior as well as anterior teeth. The needle is inserted into the 11
canal part way and should not bind the canal sufficient room between the needle and canal allows for the return flow and avoids forcing of solution into the periapical time. When it is not binding, the solution should be ejected with little or no pressure, on the plunger during the shaping and cleaning of the canal care should be taken that canals are always full of fresh solution. A perforated irrigating needle deliver irrigant 360째 in the canal, and large volumes of the irrigant solution physically remove more material it has been claimed. Disadvantage is that it is delicate and bends out of shape easily. MICROBIAL FLORA The basis of pulpal disease and the ultimate death of the dental pulp is found in the science of microbiology, clinician must recognize the cause and effect of bacterial invasion of the pulp tissue, what occurs to the bacteria when treatment ensures and final consequences when treatment is completed.
BRIEF HISTORICAL PERSPECTIVE In 1894 Miller became the first researcher to identify bacteria in the diseased pulp.
In 1910 William Hunter described dissemination of microorganisms, which became formally known as â€œfocal infection theoryâ€?, which caused concern with oral focal infection. In 1939 F. Wilfred Fish investigated zones in tissue that formed in response to infection, recognizing four zones of reaction. Appleton suggested that without bacteria no need would exist for endodontic treatment supported by the study of Cabechashi and colleagues. Appleton maintained that the function of root canal therapy is to render the canal and periapical tissue sterile and a bacteriologic examination has therefore necessary. Since 1901 the question of the validity of culturing remains and the controversy continues. Earlier studies described a flora consisting predominantly of aerobic and facultative anaerobic microorganisms. The differences in flora, as reported by different investigations over the past 5 years, are the result of improved technology in sampling such as new anaerobic culturing techniques, new and improved culturing media, and more sophisticated methods of isolation and identification of microorganisms and also the interest of the investigator. In 1919, Henric and Hartzell (began indentifying bacteria from the dental pulp) found that 65% of the organisms were streptococci, 20% were staphylococci, and the remaining bacteria were corynebacteria and yeasts. 13
In 1952, Grossman and Cristrian found that infected pulpal tissue occupied 77% gram positive cocci, 16% yeast and 5% gram negative rods. In 1973 Berg and Mord and in 1974 Kantz and Henry used anaerobic isolation and obliggate anaerobes in 27% of their samples. -
Actinomyces, Camrlobaction, Eubacteria, Fusobacteria, streptococcus and veilonells.
Bystorm and Sundquist found 87% of their isolation anaerobes.
Sandquist concluded that accute inflammation of the periradicular area is induced by combinations of bacterial strains and predominately that of bacteriocids.
Black pigmented bacteriocidal, B.gingivalis and B. endodontalis were present only in acute infections. Glick and associates were able to identify HIV (Human Immuno
Deficiency Virus) in noninflammed dental pulps of patients with AIDS through the use of polyacrylase chain reaction (PCR) test, which present in fibroblasts of pulp. Maidorf compiled a list of generalization regarding organisms isolated from root canal are : 1. Mixed infections are more common than single organism isolates. 2. The wide variety of organisms found are partially related to the periapical inserts and culture techniques of these investigations. 14
3. The invasion of dentin from the pulp has been described but the type of organisms, growth rate and variability are poorly understood. 4. Pulpal isolates are similar to oral flora with gram positive cocci predominating. 5. Organisms associated with flare ups do not differ from asymptomatic canal isolates. 6. Cultured organism elaborate a variety of invasive enzymes. 7. The present practice of treating the source of the infection of the root canal and not the periapical tissue confirms to the findings of Hedman.
BACTERIAL PATHWAYS INTO THE PULP Bacteria enter the pulp through : 1. The crown or root following traumatic exposure of the pulp, through the dentinal tubules following carious invasion, restorative procedures including crown preparation and leaking restorations. 2. From the periodontal tissue through exposed dentinal tubules, lateral and accessory canals or apical and lateral foramina. 3. By lymphatic or hematogenous route, anachoresis is defined as the localization of transient bacteria in the blood into an inflamed area, such as a traumatized or inflamed pulp.
BACTERIOLOGIC EXAMINATION Sterility of a canal or a reduction in the number of microorganisms in a root canal canâ€™t be determined by sight and smell. Some organisms are chromogenic and not all bacteria give if noxious odour, culture is a valuable and important tool. Buchbinder showed that 10% more teeth had treated successfully on postoperative check up if they had a negative culture before obturation. Oliet and Soxin, Zolcow and Ingle have shown higher success rate under similar circumstances. Eggink found difference in healing for upto 3 years when obturated in the presence of positive or negative cultures, from the time of healing. Morqu contended that the success rate is the same whether the root canal yields a positive or negative culture at the time of obturation. The difference of 10% in result obtained by most investigators does not appear great. But in 10% of all teeth treated in presence of a positive culture is the success is unlikely. Endodontic treatment without the benefit of bacteriologic control is justified neither elonofically or ethically.
CULTURE MEDIA Culture techniques is to determine the type of organisms to be found whether it is in the canal proper or the periradicular area of the teeth. Not all microorganisms present in a root canal grow in readily available media especially obligate anaerobes, exposure to air during endodontic treatment or to the chemical agents such as sodium hypochlorite will destroy obligate anaerobes. Even though single organism of certain species is enough to initiate growth in culture media, according to Grossman maximum number of organisms needed is ten. Common endodontic culture media are: Brain heart infusion broth with 0.1% agar. Trypticase soy broth with 0.1% Agar (TSA) 0.1 Agar facilitates growth of anaerobes. Thioglycolate and glucose ascites broth. Addition of 5% Ascitic fluid or 10% horse serum will enable fastidious organism to grow. Test tubes filled to a high level, should be used for culturing to provide different degrees of oxygen tension at different levels of the culture medium. -
In viability media for growth (VMG) and stuart transport medium must strains survive for longer period.
Moller - base culture medium containing veal, veal heart, peptone prodintia an agar gel, and certain supplements will give slow grower time to produce a positive result continue about 2 weeks.
Sandquist - used pre-reduced media anaerobic box to grow anaerobes, Griffee found prereduced thioglycollate medium twice effective.
(When samples are taken) proper use of nitrogen gas over the canal orifice before samples were taken ensure canal orifice free from atmosphere oxygen. Blood agar, trypticase soy, or green/heart infusions media base may be
fortified with defibrineted blood the presence of catalase present in the hemolysed blood destroys the toxic effects of hydrogen peroxide, which is lethal to anaerobic organisms. Hemin, sodium lactate and vitamin K are added to any of the above base media and illustrated in chambers with flowing gas mixtures of almost pure carbon dioxide with less than 5% hydrogen or mixtures of oxygen free gases, such as 80% nitrogen, 10% hydrogen and 10% carbon dioxide allow anaerobic growth.
TAKING THE CULTURE The dressing from the previous visit is removed from the root canal and is discarded. A sterile charcoal impregnated absorbant point is inserted into the canal, with a spring motion to cleanse the canal surface of any trace of 18
medicament, the point is removed and discarded which will prevent carrying any of the medicament into the culture medium could inhibit bacterial growth and possible false negative culture. A fresh sterile absorbant point is now inserted into the apical foramen and is allowed to remain for at least 1 min to absorb as much periapical exudate and microorganisms from the root canal as possible. The absorbent point is removed with sterilized cotton pliers held with thumb, index and middle finger, while the plug or cap of the test tube is removed with little finger and palm of the same hand, the test tube held in the other hand is tilted slightly to prevent air contamination, the lip of the tube is flamed the absorbent point is dropped and the plug or cap is replaced and the culture tube is incubated properly.
ANAEROBIC CULTURING Fastidious process that requires special equipment and media used in a temperature controlled oxygen free environment. For clinicians wish to culture anaerobic microorganisms from samples obtained from periradicular tissue and root canal.
PERIRADICULAR SAMPLE Using an aseptic technique, insert the sterile needle into the periradicular space (i.e., swelling) aspirate fluid, eject air inside the syringe band immediately, insert the needle through the rubber septum stopper of an Anaport
vial from which the gas has been removed and eject the fluid, transport the sample within 4 hour after taking the sample to culturing department.
ROOT CANAL SAMPLE Aseptically prepare an access cavity into the pulp chamber, inject few drops of prereduced anaerobically sterilized medium (chopped meat glucose broth sandquist) into chamber, pump the medium into the root canal with a sterile endodontic file, aspirate the fluid, eject any air from the syringe immediately, insert the needle through the rubber stopper of an anaport vial and eject the fluid. If an exudate is present inside the root canal, the injection of additional medium is unaccessory for sampling.
SUMMARY AND CONCLUSION Irrigants in endodontic therapy is a must and are many, it is for the clinician to select particular irrigant, depending on the clinical observation, sterility canal configuration, the knowledge of the microbial flora, and their isolations and maintaining negative field in the canal improves the success of root canal.
Contents Introduction Goals of Irrigation Desirable Properties Irrigating Solutions Ultrasonic Irrigation Microbial Flora Bacterial Pathways into the Pulp Bacteriologic Examination Culture Media Taking the Culture Summary & Conclusion
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