Advanced Endodontic Therapy

Advanced Endodontic Therapy

Michael Peak1 and Heidi B. Lobprise2

1 Tampa Bay Veterinary Specialists, Largo, FL, USA

2 Main Street Veterinary Dental Clinic, Flower Mound, TX, USA

16.1 Principles

Standard therapeutic endodontics has rapidly progressed from an emerging science to an established part of veterinary dentistry. The excellent results from standard endodontic treatments, founded on scientifically established techniques, have resulted in the profession and the public accepting and expecting more ambitious treatments to more advanced problems [1]. Anticipation of every possible problem is not feasible; however, the more commonplace can be satisfactorily managed in a proficient manner when correctly identified. In complicated cases, however, advanced endodontic techniques may be employed to salvage teeth and circumvent procedural difficulties that might limit the success of standard techniques.

Many diverse areas of difficulty can be confronted in endodontic treatment [2, 3]. Some of the more common are access to the pulp cavity, attaining and maintaining working length, resolution of periapical pathology, complete obturation, and addressing iatrogenic injury. Perforations of the pulp cavity may result when access is complicated, tissues are diseased, or instrumentation is inappropriate for the situation. Canal abnormalities and blockages may present obstacles for adequate access, instrumentation to full working length, canal filing, canal shaping, and ultimately canal obturation. In addition, there are pedodontic endodontic considerations such as treatment of deciduous teeth and permanent teeth with immature or poorly developed root structure.

16.2 Endodontic Access

The fundamental purpose in the site of tooth access in standard endodontics is to establish an unrestricted passageway from the crown and through the pulpal cavity to the apical terminus of the endodontic canal [2]. An unimpeded pathway must be customized to expedite acceptable canal instrumentation and obturation according to specific tooth type and the individuality of the tooth’s pulp system. The goal of access design is to gain full working length to the apical terminus of the canal while providing for obturation of the apical third of the canal, yet conserving as much tooth structure as possible.

Numerous technical difficulties can be diminished or eliminated with proper access preparation [2]. A cornerstone of good dentistry has always been the conservation of tooth structure; nevertheless this should not be allowed to influence the valid selection of site, design, or execution of the actual access opening [2]. This does not suggest that an excess of coronal structure should be removed indiscriminately. It does imply the need for a competent awareness of the pulp cavity and external root anatomy and the ability to properly assess radiographic details in order to appropriately implement access and prepare the coronal approach [2]. Until imaging modalities such as cone beam computed tomography (CBCT) are commonplace, the clinician must be thoroughly knowledgeable of pulpal and root anatomy as it is interpreted with proper two‐dimensional radiographic assessment of a three‐dimensional endodontic canal [2]. Failure to follow these basic steps may unnecessarily invite complications.

Tooth or restorative structure that is unsound or unsupported in the access pathway is better removed prior to initiation of endodontic treatment. Such action assists in maintenance of asepsis, provides for a better evaluation of restorative needs prior to root canal therapy, while enhancing visibility [2]. When all diseased structure is not removed prior to cleaning and shaping of the endodontic canal, contamination by debris falling or being carried into the canal may result. There are several techniques to remove material trapped in the root canal system, which are discussed in detail later in this chapter.

Failure to establish proper access to the pulp chamber and root canals is one of the most common complicating factors in root canal therapy for veterinary practitioners [3]. The pulp chamber space is typically located in the center of the crown and the root canal in the center of the root. However, the pulp cavity is a dynamic, changing, cavernous space. With age, the cavity diminishes in size. In addition, pulpal irritation from caries, abrasion/attrition, tooth resorption, and restorative procedures can result in dimensional changes in the area of the irritation due to deposition of reparative or tertiary dentin internally. Diagnostic dental radiographs, while only two dimensional, are necessary to properly assess the anatomical relationship between the crown, the root, the angle of the root within the arch, and the general condition of the pulp cavity. When dealing with abnormal crown or root configurations or rotated teeth, radiographs often must be angled from mesial and distal aspects to provide the necessary information. Using two‐dimensional radiographs as a guide for an access opening in a three‐dimensional tooth can sometimes be misleading. CBCT has been shown to be superior to dental radiographs in the detection of small areas of bone loss in endodontically involved teeth and for mapping root canal morphology and finding extra roots/canals (see Chapter 3 – Oral Radiology and Imaging).

In some cases, access can be made through the pulp exposure at the fracture surface. If the access through the pulp exposure is not ideal, or if there is no pulp exposure, the pulp canal must be accessed independently. Although each tooth must be assessed individually, certain generalities can be made on the typical location of approach to the more commonly accessed teeth in the dog [4]. The typical entrance to the incisors may be found on the central lingual aspect of the crown 1–2 mm above the free gingival margin. Additionally, a similar labial approach may be used, though commonly not the choice in human dentistry due to esthetics. Cuspids or canine teeth are accessed 1–2 mm coronal to the free gingival margin on the mesial aspect of the crown to allow a straighter line access to the apex. The individual canals of two‐rooted premolars should have the access openings made on the buccal aspect over the center of each root near the cusp’s margin, as determined by physical palpation of the juga and radiographs. The approach to the lower first molars is similar except that access is most commonly made on the lingual surface for the mesial root and within the occlusal surface for the distal root. The other two rooted molars have access achieved on the occlusal surface directly over the roots to be entered. The maxillary fourth premolar presents a moderate challenge in the access to the mesial roots, especially the mesiopalatal root. While the distal root access is similar to other premolars, a transcoronal access has been described, using distinct angles [5]. This described technique is most useful to the novice clinician in gaining an understanding of the basic approach. In most fractured teeth, however, normal anatomy has been destroyed and determining an adequate exposure by mental extrapolation is required. Palpation of the mesiobuccal root juga and comparison to the actual location of the mesiopalatal root’s cusp typically affords sufficient visualization to attain suitable lines of access determination. The actual opening is generally made between these two determined points and approximately 2–4 mm above the gingival margin on the buccal aspect of the tooth. One potential complication in access of the mesial roots is accidental perforation into the furcation between the mesial roots. To avoid this, once the pulp chamber has been identified and one of the pulp canals is found, the operator can insert a small (number 1/2 or number 1 size) round ball bur or small pear‐shaped bur (without engaging power so the bur is not spinning) into the access until the bur encounters the pulp floor. Once the depth of the floor has been established, the power is engaged to the high‐speed handpiece, causing the bur to spin. As the bur is spinning, it is removed from the canal in a sweeping motion to remove the ceiling of the pulp canal in the direction of the yet to be identified pulp canal. In many instances, this will remove only the dentin overhang that is blocking insertion of a small endodontic file into the desired canal. Use of this technique can help identify either the mesiobuccal or mesiopalatal canal yet helps reduce the chance of iatrogenic perforation. Three‐rooted molars may be accessed with a Y‐ or V‐shaped opening on the occlusal surface that exposes each individual canal system. The first access is typically made over the lingual or palatal root, with extension of the access with a high‐speed bur and following the chamber to expose the two buccal root canals. Attempted straight‐line access of the buccal roots initially will periodically lead to chamber perforation due to the angulation of the roots. Additionally, the V‐ or Y‐shaped access aids in the detection of ribbon canals associated with fused distal and palatal roots, which are not uncommon in the upper first and second molars.

With calcified or difficult to find canals, magnification and transillumination can help with their location. In human endodontic therapy, complete preparation of the pulp chamber to visualize the chamber floor can be combined with placement of a dye or sodium hypochlorite, which will form bubbles over the canal [6]. When these basic parameters are not properly followed, problems such as failure to locate all canals, excessive gouging, and even perforations of the chamber walls and floor may occur [6].

16.3 Abnormal Canals

In veterinary endodontics, it is uncommon to encounter pulp canals that are of abnormal configuration, dystrophic, or have excessive linear calcification [7]. However, idiosyncrasies such as supernumerary roots and anomalous configured root systems like ribbon canals must be detected either by visualization or radiographs. Failure to recognize these quickly can lead to unnecessary delays and problems. Dystrophic canals may be confronted when standard root canal treatment is attempted on teeth that have previously had direct or indirect pulp capping performed with certain agents. Calcium hydroxide‐type products can stimulate an increased layering of tertiary dentin within the pulp cavity, causing dystrophic areas for instrumentation [8].

Most cases exhibiting radiographically fine or unidentifiable canals or other calcification endodontic canal blockages are treatable with non‐surgical root canal therapy. Successful identification of calcified orifices requires the use of a knowledge of normal dental anatomy, quality two‐dimensional radiographs, and a good three‐dimensional imagination. With these, access exploration is initiated using a small size ball bur directed toward the logical location of the endodontic cavity. Accurate pre‐operative as well as frequent operative radiographs are an absolute necessity for assessment of bur orientation and depth penetration. The search for the canal can be aided with a smooth broach or Pathfinder® (Kerr Co., Romulus, MI) to assist the clinician in identification of the orifice.

Once located, the obstructed canal must be negotiated. At this juncture, the pathfinder can continue to be used or substitution with a No. 8 K‐file is acceptable. The No. 6 K‐file is usually too weak to allow appropriate pressure and the No. 10 may be too large. Instrumentation should be performed with a file that is long enough to reach the apex but not excessive in length as the longer the instrument the more tactile sense is lost [9]. If the canal is curved, a slight curve can be placed 1 mm from the apical tip of the instrument to aid in its correct direction of orientation. Endodontic stops should always be used, and if the instrument is curved, a directional stop is mandatory. The directional stop’s pointer should be aligned to indicate the direction of the instrument’s curvature.

Chelating agents such as ethylene‐diamine‐tetra‐acetic acid (EDTA) can be used to aid in the dissolution of inorganic calcification within the canal. Products such as RC Prep® (Premier Corp., Plymouth Meeting, PA), a white paste‐like substance, combine EDTA, urea peroxidase, and lubricant for use directly on instruments introduced into the canal. Frequent copious irrigation with EDTA solution, sterile saline, dilute chlorhexidine, or full or half‐strength sodium hypochlorite (3–6% NaOCl) is important to remove debris as the instrument is advanced. Sodium hypochlorite should be used with care in suspect perforation or open apex cases as it can result in serious complications should it enter the periodontal or periapical tissues. Care should be taken to use true windowed or slotted endodontic irrigation needles in irrigating within fine canals as injection needles may easily occlude a canal, preventing irrigant from flushing around the needle, thereby forcing irrigant and debris through the apex.

When obstruction is met, the file (K‐file or reamer) should have gentle force applied and be worked in a very delicate clockwise–counterclockwise rotation. This is sometimes called “stem winding” or balanced force instrumentation. This action is slowly continued, along with alternating larger files, removing dentinal shavings from the file flutes and flushing the canal frequently until the canal terminus is encountered. Once appropriate working length is verified radiographically, a filing or up and down action should be used until the instrument is functioning in a clean, free movement. Normal standard hand instruments can commonly be followed from this point as long as regular recapitulation of the canal with smaller files is employed to loosen any debris or dentin and maintain full length with each enlarging file. The use of ultrasonic activated endodontic instruments has been advocated for passive penetration of calcified or blocked canals [6].

16.4 Procedural Errors

16.4.1 Instrumentation Errors

Gouging is the penetration of the pulp chamber floor but not completely through the root/crown wall, typically with burs or files during exploration for root canals. Canals can also be gouged, but this is more appropriately termed ledging or hedging. If gouging results in compete extension into the periradicular tissues or outside the crown, this is called a perforation.

A ledge is a gouge or false canal created during instrumentation with excessive apical pressure primarily associated with curved canals (Figure 16.1). Ledging also causes loss of working length, but usually can be corrected with use of a proper treatment protocol. Prevention comes from avoidance of excessive apical instrument pressures until the file is working freely in the canal, use of lubricants on the files, use of flexible materials/files such as nickel titanium (NiTi files), and use of pre‐bent files with properly placed directional stops when working in curved canals. Early recognition of the error is important and the dilemma is usually obvious if routine radiographs are being taken. Unfortunately, if missed, these errors may lead to perforation and a poorer prognosis of the endodontic procedure. Even when caught early, the novice will find that attempts at reestablishment of the original canal pathway can be frustrating. This is overcome in most cases by placing a 45° acute bend 3 mm from the tip of a pathfinder or size 8–15 K‐file. A directional endodontic stop should be placed so that it points to the direction of the angle of the instrument point. The instrument should be well lubricated. The tip of the instrument should be directed away from the ledge. The spring action of the bend of the instrument will normally force the tip to bypass the ledge and compel it to enter the true root canal passageway, thus allowing the correct working length to be achieved. Once the actual canal is patent, the subsequent files may be treated similarly until the filing is complete.

Illustration of ledging or transportation displaying a nickel titanium rotary file inserted in a downward tilted manner into the pulp of the tooth.

Figure 16.1 Ledging or transportation.

Source: Courtesy of Josephine Banyard.

Another procedural error encountered that results in a change of working length is zipping or elliptication (Figure 16.2). These terms refer to when an overextended file transports the outer wall of the apical foramen [6]. The primary indicted cause of zipping is failure to pre‐bend files, excessive rotation of instruments, and use of instruments in curved canal systems that are too stiff. Two complications are common with this phenomenon, elbow stricture and apical perforation. In elbow stricture, the root canal has decreased the diameter just before the actual terminus of the canal, creating a larger space just before the apical delta. When obturating the canal, this leaves a potential unfilled apical void or vault in which fluids can accumulate and result in the eventual failure of the endodontic procedure. The best approach to treat this problem is further enlargement of the canal to remove the stricture and frequent irrigation to remove any dentinal debris.

Diagram of a tooth with lines indicating the elbow, zipping, and apical vault.

Figure 16.2 Elbowing within the apical portion of the root canal contributed to the apical vault and zipping or elliptication.

Source: Courtesy of Josephine Banyard.

Stripping is an endodontic complication that results in lateral wall perforation (Figure 16.3). This refers to the thinning of a lateral root canal wall, usually in the direction of the root tip curvature. Overzealous instrumentation in the midroot areas is the primary suspected cause, with perforation eventually occurring if not caught early. Use of judicial filing pressure away from the curvature of the root tip and/or toward the bulkier portion of the tooth root (anticurvature filing) is normally sufficient to prevent stripping. Stripping, when detected early, can be handled by appropriate instrumentation, as previously described. Proper radiographs normally provide the differential diagnosis between lateral wall perforation of stripping and apical perforations. Treatment of lateral wall perforation is best dealt with in a two‐stage non‐surgical endodontic procedure. Non‐affected roots can have standard endodontic treatment completed. The perforated root should be filled with mineral trioxide aggregate (MTA) (see the discussion regarding perforations that follows).

Diagram illustrating the stripping of the canal wall displaying the tooth with the nickel titanium rotary file inserted in an upward tilted manner into the pulp of the tooth.

Figure 16.3 Stripping of the canal wall can result in lateral perforation.

Source: Courtesy of Josephine Banyard. Perforations

Perforation is an accidental mechanical extension through the pulp chamber into the oral cavity or the periodontal tissues [2]. Should this occur, recognition of the problem as soon as possible can reduce damage to the periradicular tissues. Canal hemorrhage, one of the most common clinical indications of perforation is continued bleeding into the chamber from the exposed periradicular tissues. When dealing with perforations into the gingival sulcus or coronal to the free gingival margin, bleeding may or may not be encountered. If this type of perforation is noted, the following treatment protocol can, in many instances, be employed. First, control any hemorrhage. This may be accomplished with a dry cotton pellet or the large blunt end of a paper point. If the patient is healthy, the use of epinephrine (1 : 50 000) or another hemostatic agent on the pellet can be considered [2]. Epinephrine‐containing agents should be used cautiously in animals with endocrine imbalances or heart disease. This is followed by placement of a gutta‐percha point or paper point into the yet to be filled root canals to prevent restoratives from entering and sealing them off. Next place a temporary filling material into the perforation, such as Cavit‐G® (3M, St. Paul, MN) or Intermediate Restorative Material (IRM ®) (Dentsply/Caulk Co., Milford, DE). The root canal procedure should now be completed. Once the root canal procedure is completed, permanent restoration should be placed to seal off the perforation. If the perforation is in the sulcus or furcation, there is a probability that a persistent periodontal lesion with migration of the gingival margin may occur [10]. Additional periodontal treatments, such as gingivectomies or apical repositioning, may prove necessary.

The prognosis for perforation repair is improved with more apical lesions, but these may be more difficult to access for the repair procedure [11]. The perforation should be attended to and sealed as soon as possible. Hemorrhage must be controlled to obtain a seal in most cases [2]. Control can be facilitated with placement of saline moistened followed by dry paper points. While waiting for any bleeding to stop, any additional canals may be treated with standard root canal therapy. If hemorrhage cannot be adequately controlled, then calcium hydroxide paste may be placed along with a temporary filling and allowed two to three weeks before final treatment is attempted. Once the bleeding has been controlled, filling of the endodontic canal with MTA coronal to the level of the perforation in the affected root may be completed [11]. Once the perforation has been sealed with MTA, final restoration may be placed. These endodontically treated teeth should be carefully followed with radiographs. No references for exact follow‐up times are found for dogs, but the author usually recommends dental radiographs at 6, 12, and 18 months post‐operatively, followed by annual radiographic examinations thereafter.

Apical perforation is the condition of an instrument extending beyond the apical delta. It is typically associated with one of two scenarios. Loss of the apical constriction (apical stop) commonly occurs due to root resorption from disease or excessive instrumentation. Either of these situations may lead to instrumentation damage of the periodontal ligament and alveolar bone, along with possible inoculation of the area with debris and bacteria. Additionally, in an open apex, overfilling and a poor apical seal, as well as potential patient discomfort, may occur. Continued hemorrhage into the canal is another common sign. Although continued hemorrhage can be an indication of over‐instrumentation, it is more commonly an indication of under‐instrumentation with pulp tissue remnants. Differential diagnosis is often evident with good‐quality intraoral radiographs. Prevention comes from appropriate use of instrument stops, quality operative radiographs with periodic verification, and attention to detail during instrumentation. Once apical perforation and loss of apical stop occurs, control of hemorrhage is the first step. A new apical stop must then be established within the confines of the root canal system without excessive loss of structural integrity. This is accomplished by establishing a position with the endodontic file tip approximately 1–2 mm from the apex radiographically. With stops in place at this newly established working length, instrumentation should continue to two or three file sizes larger than the first file that shows binding at the tip. This is commonly known as the “Backup Technique” (Figure 16.4). Once the apical stop has been established, MTA can be placed at the apex of the root and the endodontic obturation completed thereafter. If the perforation is large enough to allow gross overextension of root canal obturation materials, a surgical approach to the root apex with apicoectomy and retrograde filling or extraction is advised.

Image described by caption.

Figure 16.4 The backup technique and a tooth without an apical stop. The dotted lines indicate the area of instrumentation that allows the reestablishment of the apical ledge or stop for standardized endodontic treatment.

Source: Courtesy of Josephine Banyard.

16.4.2 Procedural Blockage

Endodontic canal blockage is the obstruction of a once‐patent canal preventing full instrument access to the canal terminus. Most blockages result from the packing of dentinal chips, cotton pellets, paper points, or a piece of fractured instrument within the canal [11]. Loss of working length due to dentinal chip accumulation (dentinal mud) at the apical third of the canal can usually be attributed to too rapid an increase in file size, an insufficient irrigation technique, inadequate recapitulation, and lack of routine radiographic evaluation [11]. Once the condition has occurred it can be exceptionally difficult to correct. Use of chelating agents with an EDTA component such as RC‐Prep® can be of some help. Its action softens inorganic debris such as dentinal chips. When used in cooperation with reinstrumentation and frequent irrigation with EDTA solution or 3–6% sodium hypochlorite may facilitate the reestablishment of the working length. In other cases, it is a procedural measurement or recording error, and not a true loss of working length. This may occur from improper angular placement of the stop on the file, which results in variations of the measurement to working length according to which side of the file is used to make the measurement.

Paper points or cotton pellets lost in the pulp canal can pose a significant challenge. These can, in most cases, be removed with the delicate assistance of a barbed broach or file. Broken instruments in the canal may sometimes be removed by access enlargement and the use of a pair of mosquito forceps to grasp the instrument end. Care must be maintained not to remove excessive amounts of dental tissue, thus producing unsound tooth structure. The use of a magnetized file, spreader, or plugger can be of assistance with loose instrument pieces. Many spreaders and pluggers with a high ferrous content can be magnetized in the same fashion as screwdrivers with a strong magnet or magnetizer.

Ultrasonic instruments have been demonstrated to be one of the best ways to manage obstruction retrievals in the root canal [12]. Ultrasonic instruments and techniques involving them are commonly used to disengage cements and loosen solid objects and material from the frictional hold of the root canal. In some cases, by orienting the coronal canal access opening in a downward position and then placing an ultrasonic scaler in contact with the tooth, the fragment may vibrate out of the opening. With those that are more tenacious and in the coronal part of the canal, a different approach can be taken. The access can be slightly enlarged and the scaler placed against the exposed portion of the fragment to loosen it with activation of the ultrasonic tip. With deeper instrument fragments, a spreader or plugger may be placed in direct contact with the end of the instrument and the ultrasonic scaler touched to the spreader and activated to vibrate the fragment indirectly with the ultrasonic energy. In other cases when the instrument fragment cannot be loosened, a Gates Glidden drill can be used to widen the area immediately above coronal to the fragment. Canal obturation, in some cases, can then be attempted by leaving the fragment and bypassing it with instrumentation to complete the root canal procedure. Occasionally the bypass instrument, when in lateral contact with the instrument fragment, can be energized with an ultrasonic scaler tip and utilized to loosen the fragment. If the instrument fragment is bound firmly at the apex with no canal distal to the fragment, a sealer may be introduced around it, forming an apical seal, and the procedure can be completed. In these cases, the owner should be advised of the situation and routine rechecks performed for signs or symptoms of failure. The alternative to this would be surgical access of the apex of the root, apicoectomy, and retrograde filling (Figure 16.5a to c). If the fragment is not at the apex and cannot be bypassed, a surgical procedure with a retrograde filling would be advisable.

Image described by caption.

Figure 16.5 Radiographs of file tip separation and management: (a) tip of the file lodged in the apical region, unretrievable; (b) orthograde obturation of the canal to the level of the file tip; (c) completed apicoectomy and apical fill.

16.5 Tooth Resection, Root Resection and Hemisection

The term sectioning comes from the Latin word sectus meaning to cut, where resection comes from the Latin word resectus meaning to cut off. Root resection (root amputation) involves removing just the root portion, while retaining the entire crown [13]. Hemisection indicates a two‐rooted tooth being cut through the furcational area into two pieces, and trisection is cutting a three‐rooted tooth into three root–crown segments [13]. If any portion of the tooth is removed, there is partial tooth resection.

Resection is performed for many reasons such as root fracture, root perforation, root resorption, an endodontically inoperable tooth or root, periodontal disease, tumors of the jaws, or fractures of the jaws. Root resection involves a horizontal or angular cut to remove the root from the cervix of the tooth. This is usually accomplished with a high‐speed dental handpiece using a carbide steel or a diamond cross‐cut bur. To gain access to the furcation area, a gingival flap and possible slight alveolar bone reduction may be necessary in some cases, although in periodontal disease sufficient exposure may already be present. Root resection allows for the functional crown structure to remain intact, as compared to tooth resectioning. Currently in veterinary dentistry both are performed, but tooth resectioning is the more traditional because of the greater ease and speed of procedure. The mandibular first molar is a frequently resectioned tooth in the dog because of periodontal disease involving the distal root, or in cases of jaw fracture [13]. Vital resectioning should be approached with appropriate deliberation because of the risk of loss of pulpal vitality as in any pulp amputation and direct pulp capping (DPC) procedure. For this reason, complete standard endodontics on resectioned teeth deserves serious consideration.

16.6 Immature Deciduous Teeth

Disease and fractures of deciduous teeth occur in young animals. Treatment is determined by the extent of structural damage of the crown and root, degree of physiological or pathological resorption of the root, pulp vitality or lack of it, and the strategic value of the tooth.

As a rule, due to the short functionality (two to five months in most dogs and cats) of the deciduous teeth, extraction is usually the best treatment. On occasion, retention of the tooth may be considered advisable in order to maintain the occlusal spacing and/or interlock. The mandibular canine (#704/804) and the maxillary third incisors (#503/603) can be of strategic importance in maintaining the occlusal pattern in occlusions that are tight with an inclination toward a Class III malocclusion. Maintaining these teeth may aid in holding the occlusion in a more normal and functional pattern for the individual. Other teeth may also be of importance in maintaining proper spacing in certain situations. When it is desired to maintain a tooth that still shows indications of pulp vitality, a pulpotomy with DPC and a permanent restoration of composite or glass ionomer is advised. If the tooth shows indications of irreversible pulpitis, by continued pulpal hemorrhage following pulpotomy or other signs, the pulp should be extirpated and the tooth treated as non‐vital.

In non‐vital teeth, the treatment protocol is greatly influenced by the state of the root structure based upon pathological and/or physiological resorption. Instrumentation of the canal must be performed carefully so as not to injure the permanent tooth bud by apical perforation of instruments, irrigants, or debris and bacterial inoculation. Radiographs should be taken to establish the working length, which should be 1–3 mm short of the current apex, so preparation takes place inside of the root canal [14]. Endodontic stops should be placed at the working length on all instruments to insure safety of the permanent tooth bud. Irrigation should be made with liberal amounts of sterile normal saline and instruments coated with an EDTA chelating disinfectant. If the apex is intact the canal can be filled with a thick paste of zinc oxide and eugenol (ZOE) [15]

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Aug 15, 2020 | Posted by in GENERAL | Comments Off on Advanced Endodontic Therapy
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