CS3-2. Smear Layer and Irrigation PDF

Assist. Prof. Dr. Dilan KIRMIZI Endodontics Department SMEAR LAYER and IRRIGATION Learning Objectives of This Course: At the end of this course, students should be able to:     describe the smear layer effects on endodontic treatment list the factors to be considered and clinical relevance of...

Assist. Prof. Dr. Dilan KIRMIZI Endodontics Department SMEAR LAYER and IRRIGATION Learning Objectives of This Course: At the end of this course, students should be able to:     describe the smear layer effects on endodontic treatment list the factors to be considered and clinical relevance of root canal irrigation classify the various irrigation solutions and activation techniques describe the appropriate irrigation protocol for the endodontic case In order to produce a sterile environment and a hermetic seal, root canal treatment relies on the elimination of infected pulpal tissues, bacteria, and their toxins. During root canal instrumentation process, huge amounts of dentin debris combine with vital and necrotic pulp tissue remains produce a layer of organic and inorganic material called the smear layer that may also contain bacteria and their by-products. It can prevent the penetration of intracanal medicaments into dentinal tubules and influence the adaptation of filling materials to canal walls. Irrigation is defined as “to wash out a body cavity or wound with water or a medicated fluid” and aspiration as “the process of removing fluids or gases from the body with a suction device.” The elimination of pulp remnants, microbial toxins and germs accomplished by chemo-mechanical debridement, is necessary for the success of root canal therapy. Because of the anatomic complexity of the root canal system, mechanical instrumentation cannot remove all the infected tissues and bacteria present in isthmuses and ramifications. Therefore, the use of irrigant solutions in association with mechanical instrumentation (Chemomechanical preparation) is required to clean the root canal system. The aims of root canal irrigation are to:  reduce intraradicular microorganisms and neutralise endotoxins 1  dissolve vital or necrotic pulp tissue (organic debris)  lubricate the canal walls and instruments  facilitate removal of dentine particles and debris  Opening of dentinal tubules by removal of the smear layer The main requirements of a root canal irrigant are:  To have a broad antimicrobial spectrum  To have the ability to solve tissue  To have the ability to penetrate areas inaccessible to root canal instruments  To have low surface tension  To remain stable in solution  To be relatively cheap  To be an effective germicide and fungicide  To be non-irritating for periapical tissues  Not to be antigenic, toxic and carcinogenic to tissue cells  To be able to completely remove the smear layer and disinfect the underlying dentin and tubules  Not to stain the tooth structure  Not to be negative impact on the physical properties of exposed dentin  Not to have a negative impact on the sealing ability of root canal obturation materials  Easy to use A. Rules to Considered During Irrigation 1. The relevant tooth should be examined both radiologically and clinically before treatment. 2. The practitioner should have knowledge about the anatomy of the region in which he/she will work. 3. Rubber-dam must always be used 4. During irrigation of the canals, excessive pressure should not be applied and the tip of the syringe should not be squeezed into the canal. 5. The injector needle should move easily in the canal. 2 6. Irrigation solution should be introduced slowly into the canal. 7. Special syringe tips should be used for irrigation (30 gauge). 8. When injecting solution into the canal, the solution should be seen flowing out of the pulp chamber. 9. The syringe to be used for irrigation should be specially marked to distinguish it from the anesthesia syringe. 10. The necessary treatment plan should be implemented without panicking during complications that may occur. B. Essential Endodontic Irrigants 1. Saline 2. Sodium Hypocloride 3. Chlorhexidine (CHX) 4. Chelation agent and acids 5. Irrigation solutions with detergent 6. Hydrogen peroxide 7. Iodine potassium iodide 8. Other recent irrigants 1. Saline (NaCl)  Saline is mostly preferred for its mechanical properties and biocompatibility with surrounding tissues.  It is an isotonic solution (contains 0.9% NaCl - Sodium Chloride).  Its antimicrobial effect is controversial. 2. Sodium Hypocloride (NaOCl)  The most widely used root canal irrigant is sodium hypochlorite (NaOCl).  The tissue-dissolving capability of NaOCl is superior to all other irrigants. In concentrations of 1% to 5.25%, NaOCl dissolves vital and necrotic pulp tissue and organic components of both dentine and the smear layer. 3  NaOCl displays a strong antimicrobial activity with comparatively short contact times and is more effective against the microbial biofilm compared with other irrigants. NaOCl is able to neutralize or inactivate lipopolysaccharides.  NaOCl has a good solvent effect against organic structures, is antimicrobial, diffuses easily into dentin walls due to its low surface tension, and is easily available and cheap.  The effectiveness of NaOCl has been shown to be dependent on the concentration and duration of exposure.  The major disadvantage of NaOCl is its low ability to remove the smear layer.  Care should be exercised at all times to prevent inadvertent and accidental extrusion of NaOCl into the periradicular tissues as this may result in tissue damage accompanied by varying degrees of pain, swelling and bruising. 3. Chlorhexidine (CHX)  CHX should be used in a concentration of 0.12% to 2%.  CHX is a wide-spectrum antimicrobial agent, active against gram-positive, gramnegative bacteria and yeasts. Has less effective against gram-negative bacteria, which are predominantly found in primary endodontic infections  Disadvantages; CHX does not possess any tissue dissolving ability and is unable to neutralize lipopolysaccharides. Its antimicrobial activity that is strongly reduced by the presence of organic matters such as dentine, inflammatory exudates and serum albumin. 4. Chelation Agent and Acids Chelating agents act by chelating Ca+2 ions in dentin. This effect makes the canal walls less resistant to instrumentation. 4.a. EDTA (Ethylenediaminetetraacetic acid)  EDTA is generally used in a concentration of 17% (pH7) and can remove the smear layers when in direct contact with the root canal wall for less than 1 minute.  Remove the mineralized portion of the smear layer by chelation with the inorganic component of dentin. 4  EDTA alone usually cannot remove the smear layer effectively, a proteolytic component, such as NaOCl, must be added to remove the organic components of the smear layer. Even though EDTA has selflimited action, if it is left in the canal for longer or NaOCl is used after EDTA, erosion of dentin has been demonstrated. 4.b. HEDP (Etidronic acid)  HEDP (1-hydroxyethane 1,1-diphosphonic acid) is a weak chelator and nontoxic irrigant.  It is a potential alternative to EDTA because it has no short-term reactivity with NaOCl.  It can be used in combination with NaOCl without affecting its proteolytic or antimicrobial properties. 4.c. Citric Acid  Both ethylenediamine tetraacetic acid (EDTA) as a 17% solution (pH7) and citric acid (10–20%) are able to remove the smear layer more effectively.  Although citric acid appears to be slightly more potent at similar concentration than EDTA, both agents show high efficiency in removing the smear layer. 5. Irrigation Solutions with Detergent 5.a. EDTAC (Ethylenediaminetetraacetic acid & Cetrimide)  EDTAC shows similar smear-removing efficacy as EDTA, but it is more caustic. 5.b. BioPure MTAD and Tetraclean  MTAD is a mixture of doxycycline, citric acid, and a detergent (Tween 80). Based on a mixture of antibiotics, citric acid, and a detergent, are commercially available. MTAD has been recommended in clinical practice as a final rinse after completion of conventional chemomechanical preparation.  Tetraclean is a combination product similar to MTAD.  The two irrigants differ in the concentration of antibiotics (doxycycline 150 mg/5 mL for MTAD and 50 mg/5 mL for Tetraclean) and the kind of detergent (Tween 80 for MTAD, polypropylene glycol for Tetraclean). Both are capable of removing both the smear layer and organic tissue from the infected the root canal system. 5 Antiseptics such as quaternary ammonium compounds (EDTAC) or tetracycline antibiotics (MTAD) have been added to EDTA and citric acid irrigants, respectively, to increase their antimicrobial capacity. The clinical value of this, however, is questionable. The efficacy of MTAD or EDTA in the removal of the smear layer was confirmed, but no significant difference between these two solutions was reported. 5.c. SmearClear  SmearClear is a combination product containing EDTA and a detergent. 6. Hydrogen peroxide  Hydrogen peroxide (%1-30) has limited antimicrobial activity against bacteria, yeasts and bacterial spores. It has no necrotic tissue dissolving properties.  Strong oxygen-extracting solutions should be used with caution on living tissues. 7. Iodine potassium iodide  Iodine potassium iodide has low toxicity. It may cause an allergic reaction in some patients. 8. Other recent irrigants 8.a. Qmix  QMix contains a CHX-analog, Triclosan (N-cetyl-N,N, N-trimethylammonium bromide), and EDTA as a decalcifying agent.  It is intended as an antimicrobial irrigant as well as the removal of canal wall smear layers and debris. It is recommended to be used at the end of instrumentation, after NaOCl irrigation. 8.b. SmearOFF  SmearOFF is a novel smear layer removal agent recently introduced into endodontics.  It consists of EDTA and chlorhexidine gluconate. 6 C. Interaction of Irrigants 1. Interaction of EDTA and NaOCl:  EDTA reduces the amount of chlorine resulting in loss of NaOCl activity.  EDTA retaines its calcium-complex ability when mixed with NaOCl, but EDTA causes NaOCl to lose its tissue-dissolving capacity, with virtually no free chlorine detected in the combinations.  Clinically, this suggests that EDTA and NaOCl should be used separately.  In an alternating irrigating regimen, copious amounts of NaOCl should be administered to wash out remnants of the EDTA.  In modern endodontics, EDTA is used once the cleaning and shaping are completed for around 1 minute. 2. Interaction of CHX and NaOCl:  The combination of NaOCl and CHX causes brownish color changes and formation of a possibly toxic insoluble precipitate (precipitate of 4-chloraniline - PCA) that may interfere with the seal of the root obturation and causes staining of the dentin tissue.  Rinse the canal with saline before the final CHX rinse. Alternatively, the canal can be dried using paper points before the final CHX rinse. 3. Interaction of CHX and EDTA:  The combination of CHX and EDTA produces a white precipitate.  Instead of undergoing a chemical reaction, CHX formes a salt with EDTA. D. The Suggested Irrigation Protocol There is no ideal or perfect irrigation solution in endodontic practice. Therefore, it is recommended to use 2 or more types of irrigants together to increase the efficiency of the solutions, and also to use the solutions in the correct order to ensure maximize disinfection efficiency.  After access cavity preparation: flush the cavity and canal orifices with NaOCI (% 5.25); canals must always be kept wet with NaOCI (% 5.25) during preparation. 7  Between instruments: NaOCI (% 5.25)2–5 mL/canal  After shaping: NaOCI (% 5.25) 5–10 mL/canal  Removal of the smear layer: EDTA or citric acid 5 mL/canal Irrigation sequence of Vital and Devital Tooth: 1. Irrigation with NaOCI (% 5.25) 2–5 mL/canal 2. Removal of NaOCI with Saline 2mL/canal 3. Irrigation with EDTA (%17) or citric acid 5 mL/canal 4. Removal of EDTA with NaOCI (% 5.25) 2–5 mL/canal 5. Removal of NaOCI with Saline 2mL/canal 6. Final irrigation with Chlorhexidine (%2) 2–5 mL/canal (preferably on devital teeth) E. Irrigation Devices and Activation Techniques of Irrigants The smear layer’s effect, its clinical implications of bacterial contamination is a highly debated subject among scientists who are continually in disagreement in Endodontics. There is evidence in the literature that microorganisms and their metabolites present in the smear layer contribute to the endodontic treatment's ultimate outcome, either directly or indirectly. Persistent infections in these canal spaces are the main cause of many treatment failures. The obturated root canal system's apical and coronal closure is greatly improved by removing the smear layer. Nevertheless, some researchers argue that the moist effect of the smear layer has a positive effect on the adaptation of some root canal paste to the dentin wall. Despite the proliferation of irrigants and irrigation techniques, the ever-difficult and problematic smear layer elimination needs to be looked upon. Studies in the literature have reported the inadequacy of various irrigation solutions for the complete removal of calcium hydroxide from root canal walls. Therefore, activation of the irrigation solutions used with various devices is recommended to maximize their effectiveness. 1. Manual Dynamic Agitation by Gutta Percha Cone  Use of apically fitting gutta-percha cone in an up-and-down motion at the working length. 8  Although this facilitates the exchange of the apical solution, but the overall volume of fresh solution in the apical canal is likely to remain small. 2. Syringe  Irrigation solutions are commonly delivered using specially designed endodontic needles and syringes.  Flexible open-ended irrigation needles are recommended so that the needle can be bent according to the canal curvature. The needle must not be jammed into the canal and the irrigant must not be delivered with unnecessary force.  The smallest needle recommended for root canal irrigation is 30 gauge (ISO size 30)  IRRIFLEX®, a flexible root canal irrigation needle has recently been introduced. The tapered shape of the needle adapts to the shape of the canal. Flow thickness of the irrigant is therefore constant as the fluid moves to the coronal area, which maximises shear forces and the elimination of debris, smear layer and biofilm. 3. Sonic and Ultrasonic devices  Sonic activation devices increase shear stress on tissue debris and biofilm by penetrating areas that the file cannot touch during canal preparation due to their rapid movement. They do not have cutting activity on root canal dentin.  Example of sonic activation devices: EndoActivator, EDDY, Vibringe sonic irrigation system.  Ultrasonic activation of the solution is performed with a non-shearing ultrasonic file, which generates an acoustic micro-fluctuation within the root canal, is inserted approximately up to the working length of the root canal and is passively moved up and down.  Passive ultrasonic irrigation (PUI) is applied to increase the effectiveness of canal disinfection by agitating the irrigation solution in the canal. 4. Laser  Another approach for activating irrigation solutions in the root canal is the use of laser.  In the working mechanism of Er,Cr: YSGG laser in the root canal, secondary cavitation occurs as a result of the expansion and explosion of the vapor bubble. With the effect 9 of this cavitation, the movement of the liquid in and out of the root canal at high speed creates a liquid pump. 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