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Dental Tribune United Kingdom Edition

page 12DTà Endodontic irrigants and irrigant delivery systems Dr Gary Glassman E ndodontic treatment is a predictable procedure with high success rates. Success depends on a number of factors, including appropriate in- strumentation, successful irriga- tion and decontamination of the root canal space to the apices and in areas such as isthmuses. These steps must be followed by com- plete obturation of the root canals, and placement of a coronal seal, prior to restorative treatment. Several irrigants and irrigant delivery systems are available, all of which behave differently and have relative advantages and disadvantages. Common root canal irrigants include so- dium hypochlorite (NaOCl), chlo- rhexidine gluconate, alcohol, hydrogen peroxide and ethylen- ediaminetetraacetic acid (EDTA). In selecting an irrigant and technique, consideration must be given to their efficacy and safety. With the introduction of mod- erntechniques,successratesofup to 98 per cent are being achieved.1 The ultimate goal of endodontic treatment per se is the prevention or treatment of apical periodon- titis such that there is complete healing and an absence of infec- tion,2 while the overall long-term goal is the placement of a defini- tive, clinically successful restora- tion and preservation of the tooth. For these to be achieved, appro- priate instrumentation, irrigation, decontamination and root canal obturation must occur, as well as attainment of a coronal seal. There is evidence that apical periodontitis is a biofilm-induced disease.3 A biofilm is an aggregate of microorganisms in which cells adhere to each other and/or to a surface. These adherent cells are frequently embedded within a self-produced matrix of extracel- lular polymeric substance. The presence of microorganisms em- bedded in a biofilm and growing in the root canal system is a key factor for the development of per- iapical lesions.4–7 Additionally, the root canal system has a complex anatomy that consists of arborisations, isth- muses and cul-de-sacs that har- bour organic tissue and bacterial contaminants (Fig. 1).8 The challenge for success- ful endodontic treatment has always been the removal of vital and necrotic remnants of pulp tis- sue, debris generated during in- strumentation, the dentine smear layer, micro-organisms, and micro-toxins from the root canal system.9 Even with the use of rotary instrumentation, the nickel- titanium instruments currently available only act on the central body of the root canal, resulting in a reliance on irrigation to clean beyond what may be achieved by these instruments.10 In addition, Enterococcus faecalis and Actinomyces pre- vention or treatment of apical periodontitis such as Actinomy- ces israelii - which are both im- plicated in endodontic infections and in endodontic failure - pen- etrate deep into dentinal tubules, making their removal through mechanical instrumentation im- possible.11,12 Finally, E. faecalis commonly expresses multidrug resistance,13–15 complicating treat- ment. Therefore, a suitable irrigant and irrigant delivery system are essential for efficient irrigation and the success of endodontic treatment.16 Root canal irrigants must not only be effective for dis- solution of the organic of the den- tal pulp, but also effectively elimi- nate bacterial contamination and remove the smear layer - the organic and inorganic layer that is created on the wall of the root canal during instrumentation. The ability to deliver irrigants to the root canal terminus in a safe manner without causing harm to the patient is as important as the efficacy of those irrigants. Over the years, many irrigat- ing agents have been tried in or- der to achieve tissue dissolution and bacterial decontamination. The desired attributes of a root canal irrigant include the abil- ity to dissolve necrotic and pulpal tissue, bacterial decontamination and a broad antimicrobial spec- trum, the ability to enter deep into the dentinal tubules, biocom- patibility and lack of toxicity, the ability to dissolve inorganic mate- rial and remove the smear layer, ease of use, and moderate cost. As mentioned above, root ca- nal irrigants currently in use in- clude hydrogen peroxide, NaOCl, EDTA, alcohol and chlorhexidine gluconate. Chlorhexidine gluco- nate offers a wide antimicrobial spectrum, the main bacteria asso- ciated with endodontic infections (E. faecalis and A. israelii) are sensitive to it, and it is biocompat- ible, with no tissue toxicity to the periapical or surrounding tissue.17 Chlorhexidine gluconate, however, lacks the ability to dis- solve necrotic tissue, which lim- its its usefulness. Hydrogen per- oxide as a canal irrigant helps to remove debris by the physical act of irrigation, as well as through effervescing of the solution. How- ever, while an effective anti-bac- terial irrigant, hydrogen peroxide does not dissolve necrotic intra- canal tissue and exhibits toxicity to the surrounding tissue. Cases of tissue damage and facial nerve damage have been reported fol- lowing use of hydrogen peroxide as a root canal irrigant.18 Alcohol- based canal irrigants have anti- microbial activity too, but do not dissolve necrotic tissue. The irrigant that satisfies most of the requirements for a root ca- nal irrigant is NaOCl.19, 20 It has the unique ability to dissolve necrotic tissue and the organic compo- nents of the smear layer.19,21,22 It also kills sessile endodontic path- ogens organised in a biofilm.23,24 There is no other root canal ir- rigant that can meet all these re- quirements, even with the use of methods such as lowering the pH,25–27 i ncreasing the tempera- ture,28–32 or adding surfactants to increase the wetting efficacy of the irrigant.33, 34 However, although NaOCl ap- pears to be the most desirable sin- gle endodontic irrigant, it cannot dissolve inorganic dentine parti- cles and thus cannot prevent the formation of a smear layer during instrumentation.35 Calcifications hindering me- chanical preparation are fre- quently encountered in the root canal system, further complicat- ing treatment. Demineralising agents such as EDTA have there- fore been recommended as ad- juvants in root canal therapy.20,36 Thus, in contemporary endodon- tic practice, dual irrigants such as NaOCl with EDTA are often used as initial and final rinses to circumvent the shortcomings of a single irrigant.37–39 These irri- gants must be brought into direct contact with the entire canal-wall surfaces for effective action,20,37,40 particularly in the apical portions of small root canals.9 The combination of NaOCl and EDTA has been used world- wide for antisepsis of root canal systems. The concentration of NaOCl used for root canal irri- gation ranges from 2.5 to six per cent, depending on the coun- try and local regulations; it has been shown, however, that tis- sue hydrolysation is greater at the Fig. 1 Root-canal complex. (Image courtesy of Dr Ronald Ordinala Zapata, Brazil.) TheInternalAnatomyOfTheHumanTeeth Endo Tribune pages 11-15 Gary Glassman discusses the use of irrigants Endodontic irrigants Endo Tribune pages 16-18 Robert Teeuwen discusses using Dr Sargenti’s technique Endodontics in daily use Endo Tribune