Endodontics - Past Paper Sheet 6 PDF

6 Abdullah Al-Rawashdeh Dua’ Al-Shrouf Sana’a Aljamani 1|Page  Working Length determination in Endodontics Go get a cup of coffee or ❖ The first picture shows the apex locater...

6 Abdullah Al-Rawashdeh Dua’ Al-Shrouf Sana’a Aljamani 1|Page  Working Length determination in Endodontics Go get a cup of coffee or ❖ The first picture shows the apex locater, a device used tea, this is a long sheet and the to locate the apex of the root and its depth most important one. by using electricity ❖ The other pictures show the cases where we measure the working length of the tooth. Usually we measure it with files (K files) inside the canal and a periapical radiograph, but before we do the access cavity, we take a pre-operative radiograph and later the periapical radiograph. ❖ This photo here describes the anatomy of the apex, it is important to know the relation between these points when taking the radiograph. A is the apex of the root, but that does not mean that it’s the tooth’s exit. B is the apical constriction where we should end our treatment. C is the root canal cementum where it overlaps in this area. F is the apical foramen (the major). We always measure the foramen within 1-2 mm from the radiographic apex, so if the file was within this range, then we are on the safe side. ❖ In this periapical radiograph we can see that the file is reaching till the end of the radiographic apex. However, when working with extracted teeth like we do in labs, we can see the tip of the same file is exiting the tooth even though the radiograph shows otherwise. Working length ❖ Working length: is the maximum length of the root (in millimeters) where root canal preparation and irrigation should be terminated, we’re not supposed to get out of this area while working on the RCT and it is measured in mm ❖ Very critical step in root canal preparation and without it you cannot reach the optimum irrigation and obturation. ❖ The estimated working length is the preliminary guess of the root canal length. Often taken from the pre-operative radiographs or using the average tooth length. This estimation is 2|Page  not usually accurate, some programs have a small ruler on the side, this ruler doesn’t give the exact measurement because it’s measuring the tooth from the outside and this is not applicable in the patient’s mouth, ❖ The applicable method in the mouth is the working length radiograph with a file and the apex locator. ❖ Apex locator: an electric machine that will tell us where to stop by completing the circuit with the PDL Ways of WL determination: 1.Radiographs: it’s a good standard; you cannot start or end your preparation without taking a radiograph ❖ The files should always be within 0.5-1 mm from the estimated working length, ❖ The estimated working length is measured by the ruler - on the PC- in the lab ❖ While it’s obtained from the: 1) apex locator 2) pre- operative radiographs and 3) average tooth length (dental anatomy) in the patient’s mouth. Preoperative radiograph ❖ Tips to do when measuring the WL: Use the rubber stopper on the file, we must always keep it on the reference point (it measures the length of the file from the reference point to the tip of the file inside the root) Use the nearest cusp for reference Write the length of the file from tip to rubber stop before WL radiograph. ✓ Root canal average lengths, you don’t have to memorize it just understand it in general. You can have it posted on the wall in your clinic. ❖ Steps of WL radiographs: 1. Estimated Working Length from Pre-Operative Radiograph and knowledge of average root length. 2. Using files size 10/15, using watch-winding - rolling between fingers (30°) - until it reaches EWL. 3|Page 3. Use Apex Locator 4. Take Working Length Radiograph (use size 15 file or larger) ❖ While taking a radiograph in the clinic we must use the beam which is present in the lab and this beam is actually mobile, it can move with the patient’s head to give us the exact position of the tooth that’s on the film, and these are the film holders, we use them to keep the film in place and we take the radiograph with it, most of the time it will show us the exact position. ❖ Radiographs with multirooted teeth, especially in premolars, we must move it in a mesial or distal direction (SLOB technique), because there are multiple roots. ❖ In the patient’s mouth you won’t be able to differentiate between buccal and palatal roots until you move the beam either mesial or distal, so we must apply this rule in premolars and molar treatment. Lip clip prop file holder 2.Apex locator: like mentioned above, it’s an electric device that has an accuracy of 90%-100% when the file is 0.5-0.1 mm from apex respectively ❖ It has two parts, the lip clip and prop file holder (it holds the file to complete the circuit) ❖ It works by measuring resistance or impedance change between different tissues (hard and soft) ❖ When the file touches the periapical tissues, just through the apical constriction, the visual display will reach Zero and will produce a beeping sound. 4|Page ❖ Apex locator can be used in wet or dry canals but only in dry pulp chambers ❖ The limitations are: 1)crowns and heavy restoration (e.g: amalgam, remember it’s a metal) 2)open apex and perforations. Note that the lip clip goes to the other side of the rubber dam. (If your working on the right side it’s located on the left side) Important note: confirmational radiographs must be taken following Apex locator reading to ensure accurate measures. 3.Historical ways of determining thr WL: A) Tactile sensation: they didn’t use anesthesia so the patient would feel the file hitting the tissues. (When the patient feels pain that means that the file exited the root) ❖ By using the file to the estimated working length and detect the apical foramen or the patient feel of pain in the radicular area. ❖ Not accurate, cause patient discomfort and pushes the bacteria into the surrounding tissues ❖ When patient is anesthetized, sensations are absent. B) Paper point (check WL only, not used anymore) ❖ Blood stain the tip at WL (used to check if there’s bleeding in the apex or not) ❖ Reduce WL 0.5 mm recheck Trouble shooting in WL radiographs File too long, beyond the apex: correct the length and retake a radiograph IF the extension is more than 2 mm, we must take another radiograph again. If the file length is over-extended or shorter in the canal but less than 2 mm of the radiographic apex then, adjust the file inside the canal without taking a radiograph. Remember the radiation exposure. Look at the picture on the left, this is a very short file, the tip of the file is underextended by almost 7 mm from the tip of the root. On the other picture it’s going all the way down, you must lower it a little and take another radiograph. You will know the distances with experience. 5|Page  Step by step endodontic treatment This diagram shows the process of endodontic treatment, we will study each one separately. Intro: After cavity preparation, we must do mechanical instrumentation on the canal. The root canal is an area that we must clean and shape in a way that maintains its anatomy (we must not change its anatomy rather we should only widen it a bit so we can deliver the irrigation and obturation instruments). After doing the chemo-mechanical treatment we should close the canals (obturation) by gutta percha, because if it’s still open then bacteria will grow and cause pain and discomfort to the patient After obturation we do a coronal restoration. (Crowns for molars and direct restorations for smaller cavities) Although no treatment strategy is 100% effective at eliminating all bacteria, careful adherence to these steps is key to ensure success and reducing microbial numbers to levels conducive to healing. The biologic objectives of root canal treatment 1. Removal of all tissues, microorganisms, their byproducts and substrates from the root canal system. 2. Shaping of the root canal system to facilitate placement of irrigants, medicaments and a root canal filling. 6|Page 3. Filling of the shaped canal system coupled with an adequate and timely coronal restoration (timely means that we should do the final restoration as fast as possible because if we didn’t the temporary restoration will fall out and the infection will come back). ✓ “Unshaped canals cannot be cleaned and unshared canals cannot be filled” Dr, Herbert Schilder, the founder of Root canal treatment system. Definitions Cleaning: It comprises the removal of all potentially pathogenic contents from the root canals system. Shaping: The establishment of a specially shaped cavity which performs the dual role of three-dimensional progressive access into the canal and creating an apical preparation which will permit the final obturation instruments and materials to fit easily (obturstion starts from the access cavity to the apical constriction by using a filling to prevent any bacterial ingress and reduce the bacterial load that was there before we start) The purpose of canal shaping is to facilitate cleaning (irrigation) and provide space for placing the obturation materials. SCHILDER’S MECHANICAL SHAPING OBJECTIVES ✓ If we’re not achieving the following objectives, then our treatment is not doing the patient any good Continuous tapering canal preparation. (The canal will start with a big diameter then it gets smaller as we move toward the AC) Cross sectional diameter narrower at every point apically, which means we must maintain the conical shape and taper of the canal. Preparation should flow with the shape of the original canal. Foramen position maintained Foramen as small as practical. ❖ The master cone: is the largest file the reaches the apical constriction without damaging the anatomy of the canal ❖ So, as we move coronally from the AC, we increase the size of our files gradually to maintain the conical shape of the canal ❖ So, the most apical point is shaped with the master cone which is the smallest file used in shaping the canal ❖ For example, if the master cone at the apical constriction is 25, the file no. 30 is used to shape the point 1mm coronal to the AC and so on 7|Page ❖ Our shaped canal will look like an inverted Eiffel Tower Basic instruments’ movements ❖ Train your knuckles, because you will use your fingers to do the tactile sensation and to be able to move the file inside the root canal treatment properly. (Meaning when we do the filing of the root canal we don’t rotate the file inside of it, instead we do certain techniques, so they don’t break inside the canal or cause damage.) ❖ The correct way to pre-curve and clean your files is always bending it slightly near the tip, also the flutes must be cleaned regularly. 1)Watch winding (https://youtu.be/KuxvpRAXNiM?si=1AUAdX3BXVcC3moV) Watch winding is reciprocating back and forth (clockwise/counterclockwise) rotation of the instrument with light apical pressure application to move the file deeper into the canal.(most used and least damaging) It is used to negotiate canals and to work files to place. 2)Reaming (https://youtu.be/1xkawB2WTJo?si=KMLPqkPBF44-zJZI) Reaming is defined as the clockwise, cutting rotation of the file. Generally, the instruments are placed into the canal until binding is encountered. The instrument is then rotated clockwise 180-360º to plane the walls and enlarge the canal space. (Sometimes you can screw it inside dentine, and that’s what makes it unsafe, so using watch wind motion is better). 3)Filing (https://youtu.be/1xkawB2WTJo?si=KMLPqkPBF44-zJZI) Filing is defined as linear push and pull motion The file is placed into the canal and pressed laterally while withdrawing it along the path of insertion to scrape the canal walls. The scraping or rasping action removes the tissue and cuts superficial dentin from the canal wall. This movement can cause packing of debris apically or even extrusion of debris into the apical tissues, watch wind movement would prevent this. 8|Page 4)Circumferential filing ( https://youtu.be/1gPa0QMo0OU?si=UM-pFs14TvBqvMPe) Circumferential filing is used for canals that are larger and or not round, usually in premolars. The file is placed into the canal and withdrawn in a directional manner sequentially against the mesial, distal, buccal, and lingual walls. 5)Anti-curvature Filing (Marwan Abou-Rass, 1980) A method for preparing curved root canals in which more dentine is selectively removed from the outer (safety zone) compared with the inner curve (danger zone) of the root. Controlled and directed preparation into the bulky/safety zones and away from the thinner portions or danger zones of the root structure, where perforation or stripping of the canal walls can occur. - Danger (inner surface) and safety (outer surface of the curvature) zones - Strip perforation -Try avoiding gates glidden in molars because it could perforate the tooth in danger zone. 6)The Balanced Force Technique The 'Balanced Force' technique was first described in 1985. In the Balanced Force technique, flexible K files with noncutting tips are rotated a quarter-turn clockwise to engage dentine of the root canal wall. Apical pressure is applied, followed by a half turn of the file in the counterclockwise direction, which effectively 'cuts' the dentine that was engaged. The process can be repeated two or three times before removing the instrument to clean the flutes and irrigate the canal. Unlike many other techniques, files are not pre-curved when used in this manner. Compared with other hand instrumentation techniques, the Balanced Force concept 9|Page was reported to allow preparation of curved canals with less canal straightening, associated with less apically extruded debris and resulted in improved canal cleanliness. Root canal preparation techniques Canal preparation (shaping) techniques can be broadly divided into those that 1) adopt an ‘apical-to-coronal’ approach such as the step-back technique 2) or those that adopt a ‘coronal-to-apical’ approach such as the crown-down technique. The step-back technique 1. Access cavity preparation: straight line access to the first curvature in the canal 2. Scouting the root canal: the pulp chamber is flooded with an irrigation solution, and a size 10 or 15 k-file is worked apically in the canal using a watch-winding motion to ensure that the coronal portion of the canal is negotiable. 3. Working length determination (estimated on a preoperative IOPA or using the apex locator) 4. Determine the initial binding file, Initial (first) binding file: is the first file that binds at the estimated working length (15 k file is the best). This gives a rough idea about the diameter at the apical constriction of the canal 5. Take a WL PA radiograph to confirm the WL. ✓ The ideal Working length radiograph should achieve the following criteria: Taken with initial apical binding file and of good quality (the minimum file size is 15). The file tip should lie 0.5–1 mm short of the radiographic apex. The Rubber stopper seated perpendicular to a reliable repeatable coronal reference point (incisal edge or cusp tip). Use the initial apical binding file at least size 15 K-file for the working length radiograph. (if it’s less than 15 you have to enlarge it) 6. Apical preparation (enlargement) phase. 10 | P a g e  Master apical file (MAF) is the largest file used to the full working length of the completely prepared root canal. It is usually 2-3 sizes larger than the initial apical binding file. Here we use the balanced force technique (watch-wind, unwind, watch-wind) The recommended minimum size of the MAF should be at least 30 in anteriors and molars, maybe 25 in premolars but never 20. Because at 20 the tightness that you feel is bec of debris at the apex, while at 25 we start to feel the real apical constrictions (tightness/tug back feeling) 7. Step back phase. Succeeding larger files are shortened by 1.0 mm increments from the previous file length (if the full length is 21mm and the MAF at this length is 30, the file used at 20 mm is 35 and so on) 8. Coronal flaring using size 2,3,4 gates glidden, succeeding larger files are shortened by 0.5 or 1.0 m increments from the previous file length. It’s done with the access cavity preparation like we learnt so far. 9. Refining phase, it’s done using the master apical file with gentle push-pull strokes to achieve a smooth tapered form of the root canal. Recapitulation ▪ Recapitulation: is accomplished by taking a small file (usually size 10) to the corrected working length to loosen accumulated debris (dentine mud) and then flushing it with 1-2 ml of irrigant (NaOCl). ▪ Recapitulation is performed between each successive enlarging instrument ▪ It goes all the way to the WL because it’s a very small file. ▪ Clean the flutes of the file and inspect it for signs of distortion, as you can see in the red circles the flutes are getting longer and longer which means the file is close to breaking, at this point throw it away and use a new one. ▪ Irrigate-Recapitulate-irrigate, when we irrigate the canal, we use a 30- or 27-gauge needle, (the higher the gauge number the narrower it is). Irrigation isn’t only used to disinfect the canal but also to dissolve the organic and inorganic substances in the canal, making it easier to refine and shape. 11 | P a g e  Step back technique It’s not adviced to use gates gliddens in posterior teeth Apical Patency Apical patency is a technique whereby small hand files (size 10 or less) are frequently inserted to or slightly beyond the apical foramen (0.5-1mm) during canal preparation. This has been advocated during cleaning and shaping procedures to ensure that the apical portion of the root is not packed with tissue, dentin debris, and bacteria With apical patency, concerns regarding extrusion of dentinal debris, bacteria, and irrigants have been raised. Seeding the peri radicular tissues with microorganisms may occur. Therefore, the use of apical patency is not biologically rational. Drawbacks of the step-back technique High risk of apical extrusion of debris, apical blockage and alteration of WL, because the apical area becomes blocked which decreases it, so when you’re doing your RCT and you feel that the WL decreased then there is a blockage that needs to be fixed. Stainless-steel files have an inherent stiffness that increases as the instrument size increases, meaning that when the files become bigger they are harder to bend, so when doing the step back technique (especially on curved canals) the bigger files may be more difficult to bend and curve, so on extremely curved canals we use special rotary instruments with different techniques (stiff instruments may cause some problems including straightening of the canal and changing its anatomy) As a result, when preparing a curved root canal, restoring forces attempt to return the instrument to its original shape, especially when the operator uses a filing motion. Therefore, in curved canals, steel instruments must be pre-curved for use, which effectively prevents them from being used in a rotary motion. 12 | P a g e  An instrument that is too stiff will cut more on the convex (outer) side than on the concave (inner) side, thereby straightening the curve. In A the stiffness and rotation movement of the file causes a ledge, which leads to the stopping of the file before WL and it causes damage to the tooth, in B the file went down then perforated a new foramen and this happened s called Apical transportation because the tooth will have 2 apical areas, in C a complete perforation took place, this one is difficult to fix and it causes problems with irrigation. Coronal flaring (pre-enlargement) Place rubber stops (so they don’t enlarge more than 2/3 of the canal) on Gates-Glidden drills #2, 3, and 4 (it’s not recommended for posterior teeth) Measure the distance between the coronal reference point to the orifice level of the canal On #4 Gates-Glidden drill set the rubber stop at the previously measured distance (coronal thirds) With the root canal filled with sodium hypochlorite, activate the slow speed handpiece and insert the #4 Gates-Glidden drill into the canal until the rubber stop contacts the reference point. Using an in-and-out stroke, plane all root canal walls with circumferential motion. Irrigate with sodium hypochlorite to remove debris. Next, set the rubber stop on the #3 Gates-Glidden drill at a distance 2mm longer than it was for the #4. Repeat the same procedure as above. Remember to irrigate following the use of the Gates-Glidden drill. Now set the rubber stop on the #2 Gates-Glidden drill at a distance 2mm longer than it was for the #3. Repeat the same procedure as above. This will result in a gradual tapering of the occlusal 1⁄2 of the root canal. The Crown-down technique In this technique the root canal is shaped in a coronal-to-apical direction A predetermined sequence of instruments of variable tapers (from larger to smaller) are required. Each instrument is advanced slightly deeper into the root canal than the preceding instrument. Just read this it’s simple 13 | P a g e  ✓ Advantages of the crown-down instrumentation technique Remove the infected coronal tissues before entering the apical part of the canal, you must not enter with files directly, instead you should do irrigation then enter with k- files. Reduce the risk of apical extrusion of debris into the peri radicular tissues. Create access for irrigants into the apical part of the root canal resulting in longer contact time between the irrigation solution and the intracanal microorganisms, that’s why we do both techniques (step back and crown down, as we start with coronal flaring) Facilitate obturation. Challenges encountered during root canal preparation Instruments must contact and plain the canal walls to debride the canal. Morphologic factors include lateral and accessory canals, canal curvatures, canal wall irregularities, fins, and isthmuses. These aberrations make total debridement virtually impossible In this pic we can only enter the red areas, while the green area in-between the canals can only be cleaned by irrigation because without the irrigation bacteria and debris will accumulate in the green area (irrigation is imp bec it’s the only material that can go into these areas) Therefore, the role of canal preparation (shaping) has undergone a paradigm shift from one fulfilling a prime debriding function, to one regarded more as radicular access to the complex root canal systems, for the irrigant and root-filling material. Neither hand instruments nor rotary files have been shown to completely debride the canal. Mechanical enlargement of the canal space dramatically decreases the presence of microorganisms present in the canal but cannot render the canal sterile. To improve the mechanical preparation techniques, antimicrobial irritants have been recommended. SMEAR LAYER Amorphous, an irregular layer consists of organic (collagen, proteins, bacteria, dental pulp tissue) and inorganic matter (minerals mainly calcium hydroxyapatite). Thickness of 1 to 5 μm and debris can be packed into the dentinal tubules in varying distances. 14 | P a g e  Evidence generally supports removing the smear layer prior to obturation, because bacteria can hide in this layer. It must be removed because: ▪ The organic debris present in the smear layer might constitute a substrate for bacterial growth. Viable microorganisms in the dentinal tubules may use the smear layer as a substrate for sustained growth. ▪ It has been suggested that the smear layer prohibits sealer contact with the canal wall, which permits leakage. ▪ When the smear layer is not removed, it may slowly disintegrate with leaking obturation materials, or it may be removed by acids and enzymes that are produced by viable bacteria left in the tubules or that enter via coronal leakage. ▪ The presence of a smear layer may also interfere with the action and effectiveness of root canal irrigants and inter-appointment disinfectants. Chemo-mechanical Root Canal Preparation Know that RCT is both mechanical and chemical treatment of the pulp, the instruments shape the canal (mechanical) and the irritants (chemical) clean it, you can’t separate them and must do them together. (The chemical is used to disintegrate organic and inorganic compounds before obturation bec even if the obturation seems to be perfect in the radiograph if there is no proper disintegration the bacteria will regrow, while mechanical is the usage of files to shape the canals, and it has nothing to do with removing bacteria) Rationale for irrigation Several studies using advanced techniques such as microcomputed tomography (CT) scanning has demonstrated that large areas of the main root-canal wall remain untouched by the instruments. To increase the efficacy of mechanical preparation and bacteria removal, instrumentation must be supplemented with active irrigating solutions. Irrigation is defined as washing out a body cavity or wound with water or a medicated fluid, it’s not only chemical but also to flush out debris. 15 | P a g e  Objectives of root canal irrigation Mechanical objectives. ▪ Dissolution of vital and necrotic pulp tissues. ▪ Lubrication of the root canal walls and instruments (to prevent the breakage of the files). ▪ Removal (flushing out) of dentine particles and debris. Biological objectives ▪ Reduction of interradicular microorganisms and neutralization of endotoxins The ideal root canal irrigant Have a broad-spectrum antimicrobial property Prolonged and sustained antimicrobial effect after use. Dissolve organic matter (dentin collagen, pulp tissue, bacterial biofilm). Non-irritating to the periapical tissues does not interfere with repair of periapical tissues, NaOCl can damage the periapical tissues. (no irrigant has achieved this ideal characteristic yet) Able to completely remove the smear layer. Able to disinfect the dentinal tubules. Do not irritate or damage vital periapical tissue, no caustic or cytotoxic effects. Has no adverse effect on the sealing ability of filling materials. Does not stain or weaken teeth. Low surface tension so it can easily flow into inaccessible areas (not viscous) Easy to use/apply. Stable in solution. Inexpensive. ▪ None of the available irrigating solutions can be regarded as optimal. Using a combination of products in the correct irrigation sequence contributes to a successful treatment outcome. Irrigation solutions Sodium hypochlorite (NaOCl).(most used when combined with EDTA) Ethylenediamine tetra acetic acid (EDTA). Chlorhexidine. Sodium hypochlorite (NaOCl) (gold standard irrigation) It is the most popular irrigating solution. NaOCl is commonly used in concentrations between 0.5% and 5.25% (you will use the 3% in the clinic), it must be pure NaOCl with no odors or other cleaning and coloring agents. 16 | P a g e  It is an excellent antibacterial agent. It also effectively dissolves pulpal remnants and collagen, the main organic components of dentin. (Sometimes it weakens the tooth by dissolving its collagen) Hypochlorite is the only root-canal irrigant of those in general use that dissolves necrotic and vital organic tissue. It dissolves the organic part of the smear layer. It should be used throughout the instrumentation phase. The weaknesses of NaOCl Unpleasant taste (if leaks through the rubber dam). Cytotoxicity (if extruded into periapical tissues it will decrease the biocompatibility) no biocompatibility Inability to remove the inorganic part of the smear layer (must be used in combination with other irrigants that can remove the inorganic part of the smear layer). Factors affecting the tissue dissolving action of NaOCl Concentration. (Increasing the concentration cause toxicity) Temperature. (the patient should be able to withstand it) Quantity. Surface contact. Contact time, you must keep changing it because it will lose its potency to disinfect. Fluid flow, fluid exchange (frequent irrigation) (The chlorine component of hypochlorite rapidly depletes and may no longer be active after 2 minutes). Amount of organic tissue (vital vs necrotic pulp). The mechanical aspects of the irrigation technique are more important than the initial available chlorine concentration. ✓ A side-vented 27- or 30-gauge needle must be used for irrigation (the pushing should be to the sides on the walls of the dentin bec I don’t want the irritant to exit the root) 17 | P a g e  Accidental injection of NaOCl into periapical tissues Symptoms and Signs of Hypochlorite Injury: Sudden severe pain. Profuse bleeding from within the canal. Extensive edema. Be careful when doing irrigation guys, Bad taste. Because this can be a permanent damage. Delayed: ecchymosis, paresthesia, secondary infection. Preventing Hypochlorite Injury The use of side vented needles for root canal irrigation Premeasure and bend the irrigation needle to a minimum of 2 mm short of the working length. Avoidance of wedging the needle into the root canal. Avoidance of excessive pressure during irrigation (use the index finger not the thumb). Keep the syringe moving within the canal. Note: Always use the needles that we were given in our lab kit, because they are the correct ones to use and because you might lose a mark or 2 in our endo lab assessments. (They have to be side vented) Managing Hypochlorite Injury Inform and reassure the patient. Irrigate the canal with saline or sterile water. Give additional local anesthetic (preferably longer acting such as Bupivacaine). Inform the patient that severe oedema and bruise are anticipated. Prescribe analgesia: paracetamol 500 mg QDS with ibuprofen 400−600 mg QDS alternating doses. Ice/cooling packs to swelling first 24 hours. Heat packs subsequently. Review within 24 hours and regularly thereafter. Prescribe antibiotics only if signs of systemic involvement. Refer to A&E if very extensive extrusion or evidence of compromised airway. Note: These points are important for the clinical rotations, just read them there won’t be questions about them. 18 | P a g e  Passive ultrasonic irrigation An irrigation technique where a small needle vibrates in a certain way resulting in an active irrigation, however it’s not for students. Manual dynamic agitation (GP pumping) Sometimes we put gutta percha in the canal while it’s wet, this pushes away the NaOCl into the tubules which is good, because it activates it which helps in removing debris and smear layer. Ethylenediamine tetra acetic acid (EDTA) A chelating agent. Used as a 17% neutralized solution (disodium EDTA, pH 7), this one is only used to help remove the inorganic components of the smear layer. However it doesn’t have an anti-microbial effect so we can’t use it as a main irritant EDTA effectively dissolves inorganic material, including hydroxyapatite, It has little or no effect on organic tissue and alone they do not have antibacterial activity. It should be used as an adjunct to sodium hypochlorite. EDTA should be used as a penultimate wash followed by final rinse with NaOCl solution before obturation. Manufactured as liquid (for root canal irrigation/removal of the inorganic part of the smear layer) and gel (Glyde®, for lubricating instruments and negotiation of tight canals). With smear layer removal, filling materials adapt better to the canal wall. Removal of the smear layer also enhances the adhesion of sealers to dentin and tubular penetration and permits the penetration of all sealers to varying depths. Removal of the smear layer reduces both coronal and apical leakage. 19 | P a g e  Chlorhexidine digluconate (CHX) Has a broad-spectrum activity against Gram positive (E faecalis, the mostly implicated bacteria in root canal failure), Gram negative bacteria, and yeast. In’s not that effective and doesn’t remove the smear layer It has substantivity; it bonds to dentinal walls, maintaining its antibacterial properties for up to 12 weeks. CHX at 0.2% (found in proprietary mouthwashes) concentrations is only bacteriostatic; to have a bactericidal effect concentration of 2% must be used. It’s not toxic It’s a mechanism of action: CHX permeates the microbial cell wall or outer membrane and attacks the bacterial cytoplasmic or inner membrane or the yeast plasma membrane. In high concentrations, CHX causes coagulation of intracellular components. Weaknesses of CHX CHX has no tissue-dissolving activity. Does not remove the smear layer. Growing concern with CHX and sensitization may result in anaphylaxis. If mixed with NaOCl, a brownish-orange precipitate is formed (parachloroaniline (PCA)), which may have mutagenic potential, if we want to use them together, we must wash CHX with saline first and dry it out then use NaOCl. There is also evidence that CHX can have a negative effect on periapical tissues’ healing, resulting in an increased odd of failure. Rules to follow during cleaning and shaping Always work in a wet canal Irrigate often Recapitulate often to loosen debris by returning to working length Never force the instrument in the canal Pre-curve your files Inspect your files for signs of distortion Clean the file flutes frequently End of Sheet #6 20 | P a g e