Frank C. Setzer and Bekir Karabucak
12.1 Introduction, Including History
Surgical treatment of teeth with apical periodontitis has a history that spans centuries. The 1880s saw the introduction of approaches to resect a root with the intention to remove necrotic portions of the apex [17, 34, 70], as well as of apical curettage to remove diseased periapical tissues, but without addressing sources of infection from inside the root canal system [199]. In the 1890s Partsch published various reports on root-end resection [181-183], leading to wider acceptance in Europe [71].
A great variety of surgical techniques have been suggested and put to use to make the procedure safer for the patient, easier to perform, and more predictable [79]. The standard approach for many years included access and root-end resection with surgical burs and the use of amalgam as root-end filling material [43, 64, 103, 176].
With improvements in chemical and mechanical cleaning for both initial root canal treatment as well as non-surgical retreatment, the usefulness of endodontic surgery was called into question as some clinical studies demonstrated extremely low outcome [7, 76].
Unsuccessful outcome of surgical endodontics is caused by the failure to address the biological issues responsible for causing apical periodontitis. For the majority of the situations the primary reason for failure of either non-surgical and surgical endodontic treatment is the continued presence of intra- and/or extraradicular infection. Success of either treatment will rely on eliminating this infection, or at least lowering the number of microbial cells below a threshold that will allow the body to resolve the apical periodontitis, and entomb them within the harsh environment of a sealed root canal system.
Persisting intracanal infection will be a source of failure after surgery if the method and materials used did not provide an effective seal. This may be aggravated if an apicoectomy leaves open a large number of tubules and canal ramifications, through which microorganisms may penetrate and cause periapical inflammation [51]. An operating microscope to identify these anatomical details together with new materials for root-end filling provides for better treatment and more predictable outcomes [79].
Modern endodontic surgery has evolved into endodontic microsurgery [125]. The surgical operating microscope gives high magnification and direct illumination. This reduces the need for beveling of the resected root and reduces the number of exposed dentinal tubules [51]. Ultrasonic instruments for in-axis root-end cavity preparation limit damage and achieve better cleaning [239], and the use of biocompatible and stable root-end filling materials support healing processes better than conventional cements [203]. This chapter seeks to provide an evidence-based overview of the state-of- the-art procedures with a focus on surgical retreatment, while contrasting the differences with traditional, historic techniques and other surgical endodontic procedures.
12.2 Surgical Endodontic Procedures
Procedures recognized as endodontic surgery include apical curettage, periradicular surgery, crown and root resections, as well as tooth replantation. Periradicular surgery includes, historically, apicoectomy (simple root-end resection without retrograde filling), in its modern context procedures such as exploratory surgeries and surgical perforation repair, as well as classical root-end surgery combining root-end resection and root-end filling. Crown and root resections include root amputations, complete root resections, hemior trisection, and bicuspidization. Replantation includes transplantation and intentional replantation, of which the latter properly belongs to endodontic procedures.
12.3 Indications
12.3.1 Tooth-related Factors
Surgical intervention is a valid alternative in cases where non-surgical retreatment is unfeasible or has failed. The general indication for non-surgical or surgical retreatment intervention is the presence of apical periodontitis. Prior to choosing endodontic surgery as a treatment option, the etiology for any persisting pathology must be carefully assessed [120], including appropriate follow-up periods for pre-existing asymptomatic lesions. Non-surgical retreatment should be the preferred option if the quality of the initial root canal treatment is deemed insuffi- cient, if there are indications of missed canals or need for a new permanent restoration.
Most odontogenic periapical lesions, including granulomas [22, 228, 236], cysts [195], and abscesses will respond positively to appropriate non-surgical retreatment. The following situations may, however, prevent periapical healing after non-surgical retreatment or present an indication for surgical retreatment after initial endodontic therapy has failed:
Complicated Root Canal Anatomy
Teeth with extreme root curvatures (>30°) or s-shaped canals, canal division in the middle or apical third, very long roots (>25 mm), or open apices (>1.5 mm in diameter) may present with challenges for non-surgical retreatment that may be difficult or cannot be overcome. Moreover, calcified canals as well as internal and external resorptions may tip the balance in favor of surgical rather than non-surgical retreatment. Iatrogenic changes to the original canal anatomy, such as blockages, transportation, ledges, or per- forations may prevent proper biomechanical disinfection [87] and leave microorganism in recesses of the root canal system in prox- imity to the constriction [274] or the apical foramen [227].
Pathophysiology of the Periapical Pathology
The overwhelming majority of periapical lesions are inflammatory in nature [18]. Nair et al. [195] classified 35% of lesions on extracted teeth as periapical abscess, 50% as granuloma, and 15% as cysts. Periapical cysts may be pocket cysts, which have direct connection with the infected root canal system, or apical true cysts, which are separated from the root [164, 195]. Of all periapical lesions, 9% were described as apical true and 6% as apical pocket cyst [195]. True cysts may be less likely to resolve by primary endodontic treatment or non-surgical retreatment [195], and may thus require surgical intervention. Periapical foreign body reactions, initiated by amalgam remnants, gutta-percha, and other endodontic filling and sealer materials, pieces of paper points, or cholesterol clefts associated with cystic lesions also occur [163-165].
Extraradicular infection may occur in the form of biofilms attached to the external root surface [257], as well as colonies of Actinomyces and Proprionibacterium species within the soft tissue lesion itself [194, 200, 229, 240]. If the initial size of the periapical defect exceeds 5 mm in diameter healing by non-surgical treatment may be impaired [168, 169]. All these scenarios are unlikely to be resolved by non-surgical retreatment, and may result in the need for endodontic surgery.
Altered Canal anatomy Impeding Non-surgical Instrumentation
Many retreatment cases display a microbiological spectrum that may be more difficult to eradicate (see Chapter 5). Moreover, as a consequence of the initial treatment, there may be alterations to the original root canal anatomy that may prevent instrument and irrigant access to all areas of the root canal system. These alterations include transportations, ledges or perforations and separated instruments. While some of these obstacles may only be obvious upon initiating a conventional retreatment attempt, some may be apparent in the treatment planning stage. The success rate of non-surgical retreatment cases with apical periodontitis together with altered root canal anatomy that could not be renegotiated is only about 40% [87]. Then, depending on the situation, including residual tooth structure and the existing coronal restoration, a choice between non-surgical retreatment followed by surgical intervention or surgical retreatment only must be made. Non-infected instrument fragments may not need to be removed, but in the presence of apical pathology removal attempts should be considered. In general, non-surgical retreatment should be attempted first for stainless steel or nickel-titanium fragments, however, it must be considered if the loss of tooth structure is justifiable [219]. Particularly at or beyond a curvature, the superelasticity of conventional nickel-titanium instruments may wedge them towards the outer curvature of the canal and make some removal attempts very difficult or impossible [179], so that sometimes a direct surgical option may be less invasive [120].
Hard Root Canal Filling Materials
A variety of root canal filling materials, including hard pastes and silver points may prevent progress during non-surgical retreatment. Resorcinol-formaldehyde pastes (“Russian Red”) [6], formerly often used in East European countries may be impossible to remove from the root canal system, requiring endodontic surgery. Newer calcium silicate based sealer materials are also known to set very hard, however, no data exists to date in regard to clinical retrievability.
Posts and Build-ups
Long, prefabricated metal posts, cast post and core build-ups and crowns [120] may require a disassembly of the existing restoration that may carry risks of root fracture, excessive tooth tissue loss or perforation, favoring a surgical approach.
Resorptions, Perforations and Root Fractures
The repair of internal or external resorptions, as well as perforations, depends on the location within the root canal or the root [219, 226]. The more coronal any resorptive defect is located, the more likely a non-surgical retreatment is to succeed [155, 170, 193, 219], the more apical, a sur- gical approach will more likely be favorable. Apical resorptions usually arrest after non-surgical retreatment, however, if a resorption progresses they may need surgical treatment as well. Vertical root fractures may require exploratory surgery for clinical confirmation. In multi-rooted teeth surgical resection of the involved root may salvage the remaining roots and tooth crown, depending on the size and location of the defect. Horizontal root fractures will not require surgical intervention for vital teeth as the apical segment stays vital even if coronal fragment is necrotic [111]. However, a surgical approach may be necessary if the tooth was infected prior to the trauma [72].
12.3.2 Patient Participation in Treatment Selection
Evidence-based practice implies that the patient is informed about treatment alternatives with associated prognoses and risks. For endodontic surgery, it should be explained that it is a true surgical procedure with potential risks of damage to adjacent anatomical struc- tures, postoperative swelling, discomfort and impaired wound healing. The patient will make the final decision based on her/his perception of advantages and disadvantages of the suggested procedures, the value they place on the tooth, as well as their willingness to undertake lengthy dental procedures, and the cost [138].
12.3.3 The Dentists' Role in Decision Making
The clinician's decision making must include a detailed medical and dental history, and clinical examination. The type of coronal restoration, presence or absence of posts, and the practitioner's skill level may influence treatment planning decisions [39, 238]. These are known to be different between endodontic specialists and general practitioners [230]. The dentist may strive for the academic success to heal a periapical lesion, whereas the patient may be more concerned about tooth survival and functionality. The decision to recommend treatment will be easier with the presence of symptoms, but more intricate for asymptomatic apical periodontitis. In particular, if surgical treatment is recommended, the clinician should have the adequate knowledge, skills, experience, and armamentarium to confidently render the procedure. Surgical procedures should only be undertaken with adequate training, though they may provide a highly predictable and expedient outcome in appropriately selected cases.
12.4 Contraindications
There may be situations where endodontic surgery may be compromised or contraindicated. This may include proximity of the surgical site to anatomical structures that could suffer severe or permanent damage, for example the mental and infra-alveolar nerves, the nasal or sinus cavities, or the palatal neurovascular bundle. Teeth with unfavorable crown-to-root ratio, increased mobility or advanced periodontal disease will have a less favorable prognosis. Systemic diseases, such as cardiovascular disease prohibiting the use of vasoconstrictors with the local anesthesia, congenital bleeding disorders, a history of intravenous bisphosphonate therapy that puts the patient at high risk of bisphosphonate-related osteonecrosis of the jaws, may not allow a surgical procedures [219]. Other situations, such as diabe- tes, immune deficiencies, or anticoagulant therapy may put the patient at elevated risks of postoperative complications or impaired wound healing. Cooperation with the patient's physician is then mandatory [219].
12.5 General Preparations for Surgery
12.5.1 CBCT Evaluation
Cone beam computed tomography (CBCT) has become a widely accepted tool for evaluation in endodontics [213, 218] (see Chapter 6), but it is limited by the relatively high radiation exposure. In surgical treatment planning, CBCT is helpful for assessment of the extent and location of apical periodontitis, of the bone thickness over pathologic defects, and of the proximity to anatomical structures such as the infra-alveolar and mental nerve, nasal and sinus cavities and adjacent root structures [74, 218]. A vertical root fractures cannot be accurately detected by CBCT due to limited resolution and beam hardening effects of root-filling materials, but a narrow vertical pattern of bone destruction can indicate its presence [44, 156]. The CBCT software will also allow the clinician to make accurate measurements of, e.g., the distance from the buccal bone surface to a root tip and the length of a root [28]. Guided microsurgical techniques have been developed that employ a preoperative CBCT together with a conventional or digital impression to prefabricate a stent that allows the surgical access bur to directly target the root tip to be resected. This may be especially useful for the resection of roots in very close proximity to important anatomical details [4, 83] (Figure 12.1a-f).
12.5.2 Armamentarium
Modern endodontic surgery is a microsurgical technique requiring specialized instruments [125]. A typical microsurgical instrument kit contains miniaturized versions of standard surgical instruments, some particularly designed for work under a dental microscope. Necessary instruments include:
• dental mirror
• periodontal probe
• endodontic explorer, and microexplorer for examination
• surgical blades, blade holder, and tissue elevators for incision and flap elevation
• periodontal curettes, surgical curettes, and mini-endodontic curettes for removal of pathologic tissues
• micromirrors and handle for inspection
• carriers and pluggers for root-end filling.
In addition to these hand instruments, the following armamentarium will be required, and are described in detail in the procedure section of this chapter:
• surgical handpiece and burs for osteotomy and root resection
• tissue retractors
• ultrasonic unit with corresponding tips for root-end preparation
• microsurgical tissue forceps, needle holder, and scissors
• miscellaneous instruments such as anesthesia syringe, college pliers, air water syringe and a micro irrigator.
Disposable items include:
• anesthetic solution,
• gauze and cotton-pellets
• hemostatic agents, dyes, saline
• root-end filling and perforation repair materials
• bone grafting and membrane materials
• sutures.
A piezoelectric bone cutting device for specific osteotomy techniques may also be useful.
12.5.3 Patient Positioning
Endodontic surgery is an option for the majority of teeth, except most maxillary and mandibular second and third molars if they require root-end preparation and filling. Correct positioning of the patient, practitioner, and assistant is key to the procedure [119, 134]. The patient's comfort and the practitioner's ability to perform the proce- dure adequately both have to be kept in mind. For endodontic microsurgery, the dental microscope will provide high magnification, co-axial illumination, ergonomic seating of the clinician, and direct vision of the resected root surface without the need for a bevel [125, 220]. Throughout soft tissue elevation, osteotomy, and root resection, the patient should remain in a position in which the long axis of the tooth being worked on is in a horizontal position. As soon as the resection is completed and verified, and ultrasonic root-end preparation begins, direct vision of the resected root surface must be obtained to avoid misalignment of the ultrasonic tip and limit the osteotomy to an acceptable size. This will be achieved by uprighting the chair when working on maxillary teeth, and further reclining for working on mandibular teeth. The original position may resume after root-end filling is completed.
12.6 Anesthesia
Local anesthesia in endodontic surgery is used for both profound analgesia and hemostasis [127]. Identification of a resected root surface requires examination under high magnification with the microscope. The hemostasis provided by the local anesthetic is achieved by adding a vasoconstrictor, typically 1:50,000 epinephrine (depending on availability, 1:80, 000 as alternative) [35, 93, 126]. The higher concentration of the vasoconstrictor reduces bleeding [93, 113, 280] if it is injected in the submucosa.
Figure 12.1 Pre-surgical treatment planning using CBCT for endodontic surgery on distal root of a first right mandibular molar. (a, b) Assessment of location of infra-alveolar nerve canal and mental foramen (arrows), allowing for distance measurements in sagittal and coronal planes. (c) Preoperative radiograph. (d, e) Postoperative radiographs, root-end filling in situ. (f) 12-months follow-up, radiographic healing observed, no clinical symptoms. Courtesy of Dr Frank Setzer, Philadelphia, PA, USA.
Concerns whether higher concentration of epinephrine has effects on the systemic circulation had been raised [258, 280]. Local anesthetics containing epinephrine 1:50,000 should only be placed in the buccal sub- mucosa (or palatal tissues, respectively), 1-2 teeth mesial and distal from the tooth undergoing surgery. These higher epinephrine concentrations are not necessary for the infra-alveolar nerve block, as it does not contribute to hemostasis in the surgical field. If direct injection in blood vessels is avoided, any cardiovascular effects should be minimal and short-lived and well tolerated by most patients. For patients suffering from severe cardiovascular disorders or who have had cardiovascular surgery higher epinephrine concentrations may be contraindicated, requiring a consultation with the patient's physician to establish a different anesthetic regimen, if advised [23, 128, 283].
12.7 Surgical Anatomy
12.7.1 Soft Tissue Anatomy
The general surgical access to the roots is from buccal, with the exception of the palatal roots of the maxillary molars. On the buccal aspect, three types of soft tissues are present, the alveolar mucosa, the attached gingiva, and the marginal gingiva. The alveolar mucosa is a thin, nonkeratinized mucosal layer covering the alveolar processes of both maxilla and mandible. It is loosely attached to the underlying bone and can be stretched and pulled by movement of the cheeks or lips. The attached gingiva is the portion of gingiva that extends from the base of the gingival crevice to the mucogingival junction.
It is firmly joined to the underlying bone and cementum and is thus immovable. The marginal gingiva is the crest of free gingiva surrounding the tooth like a collar and forming the soft tissue portion of the gingival sulcus. During endodontic surgery great care must be taken to minimize any potential scaring from the operative procedure.
12.7.2 Flap Designs
The primary purposes of proper flap design and tissue elevation are to allow for adequate surgical access to the underlining bone, root structure, and pathologic lesion, as well as to provide uncomplicated and scar-free soft tissue healing [147, 160].
A variety of flap designs had been proposed over the years [189, 263, 264, 271]. Now obsolete is the semilunar flap, a design that involves a curved incision entirely placed in the mucosa [32, 96]. Disadvantages of this flap include limited surgical access to larger periapical lesions, difficult reapproximation, and often secondary healing by granulation tissue, more postoperative swelling and pain, flap shrinkage, and, due to the incision across blood vessels and fiber lines, possible compromised blood supply to the flap and more scarring than any other designs [132]. Another design is the single vertical incision above the root, with lateral retraction of tissues to expose bone over the apex [36, 277]. While it benefits the surgical access to very long roots, and does not cut across blood vessels, its disadvantages include reduced access to larger lesion, and an increased risk of postoperative infection, as the incision is often placed above blood clot filling the osteotomy site after the surgical procedure.
The two most widely used contemporary incisions are the intra-sulcular and the submarginal flap designs.
Intra-sulcular Incision
The intra-sulcular incision dates back to 1930s [105]. It is a full-thickness flap design, allowing for healing by primary intention, and keeping the blood supply intact [96] (Figure 12.2).
Figure 12.2 Triangular sulcular flap for posterior surgery, allowing access to buccal roots of a first left maxillary molar. Courtesy of Dr Frank Setzer, Philadelphia, PA, USA.
Depending on whether one or two vertical release incisions are used, both triangular and rectangular designs are a possibility. A trian- gular intra-sulcular flap is mostly sufficient for access to the surgical site, however, a rectangular flap design may be necessary if a large periradicular lesion needs to be addressed, or more than one tooth is receiving surgery. Intra-sulcular flap designs allow for good re-attachment of the flap, and have demonstrated minimal postoperative pain and swelling, as infection of the blood clot in the osteotomy site is unlikely [96]. Disadvantages include a slight gingival recession, which can be an esthetic problem when artificial crown margins are present, particularly in the max- illary anterior area [132]. There has been also reported damage to the dental papilla [91, 262], in particular when the tissue is poorly keratinized, papilla is very thin, or when the soft tissues are not carefully managed. Adequate blood supply to the papilla with this flap design is best assured if the vertical incision joins the horizontal incision lateral to the papilla at a 90 degree angle. Particular attention needs to be paid to patients that present with a high smile line, or a thin-scalloped periodontal biotype. A variation of the intra- sulcular incision that aims avoiding these problems is the papilla base incision, where the intra-sulcular component of the incision only occurs in the buccal-cervical aspect of the tooth, but the papilla remains intact by continuing the incision line through the base of the papilla without detaching it with the flap [261]. There may be significantly less recession of the papilla if this incision is used [262].
Submarginal Incision
The submarginal incision was introduced in the 1920s [167], and further mentioned by Ochsenbein-Luebke [148]. In contrast to the intra-sulcular incision, the free gingiva surrounding the teeth will not be detached by this flap design. A horizontal, submarginal incision will be placed in the middle of the attached gingiva following the coronal margin of the teeth (Figure 12.3). Both triangular and rectangular versions of the flap are possible, with the same indications as outlined above. This flap design is better suited for areas of wider attached gingiva, in particular in the maxillary anterior area or in the presence of artificial crown margins, or other esthetically challenging situations where it is beneficial to leave gingival tissues undisturbed [91]. This flap design may be disadvantageous where the surgical access is limited, or if a large periradicular lesion is present, particularly in the coronal-apical dimension. While the flap design generally allows good preadaptation and wound healing, postoperative scarring has been observed in areas where the soft tissues are more likely to tear [132].
Figure 12.3 Triangular submarginal flap for anterior surgery, allowing access to periapical lesion associated with a right lateral maxillary incisor. Note buccal plate defect. Courtesy of Dr Frank Setzer, Philadelphia, PA, USA.
12.7.3 General Osseous Anatomy
In some scenarios, the cortical plate has been perforated by the periradicular lesion, so that simple soft tissue curettage will help to identify the root tip. If the root tip is covered, the clinician should have a strong indication of the location of the root tip from the pre-surgical treatment planning, including clinical observation and preoperative measurements gained from periapical radiographs or a CBCT. The proximity of the apices to apices of adjacent teeth, the mental foramen, the infra-alveolar nerve, or the sinus space need to be taken into consideration [112, 136, 174]. In general, the size of the osteotomy should be kept as small as possible, but as large as necessary to allow for removal of inflammatory tissues and proper execution of root resection, inspection of the resected root surface, root-end preparation, and root-end filling.
Alternative osteotomy techniques have been described. In situations with no detectable cortical plate fenestration, or where a thick cortical plate is expected a bone window technique may be employed [123]. This may be undertaken with the use of a surgical saw, or a piezo surgery device with fine-toothed saw tips. A rectangular-shaped bone window will be created, the root tips uncovered, the bone stored in a suitable salt solution), and placed back into its original position at the end of the surgical procedure. Recently, guided surgery techniques using 3D-printed stents created from CBCT scans and impressions have allowed easier access to surgical sites in intimate proximity of sensitive anatomical structures [4, 83].
12.7.4 Specific Anatomy
Maxillary Sinus
If a periapical lesion reaches or perforates the sinus, an opening to the oral cavity may be created by excision of the inflammatory tissues [104]. When a perforation has occurred or appears likely to happen, precaution needs to be taken not to displace any tissue remnants or foreign body materials into the sinus cavity. There has been debate if it is advisable to shave off the root tip and thus close attention must be paid not to get dentinal shavings into the sinus [142], or if carefully resecting the root tip as a whole while securing the apex is the preferable technique [92]. A sterile cotton gauze pad secured by a suture can be placed as a temporary barrier to block any shavings or foreign body materials from entering the sinus [125] (Figure 12.4a-b). The outcome of endodontic surgery will not be compromised by a sinus opening itself [276], as the repositioned flap will provide protection after the surgical procedure For larger openings, a bone grafting material such as collagen or a membrane covering the buccal defect may be advised. In healthy patients, antibiotics may not be necessary, but a decongestant may be advisable to prevent any pressure issues from within the sinus to disturb the wound healing.
Figure 12.4 Intra-operative protection of sinus opening after enucleation of a periapical lesion associated with a second left maxillary premolar. (a) Micro-mirror view of root-end preparation. Cotton pellet secured by a surgical thread blocking the sinus perforation in situ. (b) Situation after placement root-end filling and removal of cotton pellet. Note sinus perforation (arrow). Courtesy of Dr Karla Sermeno de Castillo, Austin, TX, USA.
Palatine Neurovascular Bundle
Palatal surgery is mostly limited to first molars. Maxillary premolars can generally undergo surgery from a buccal approach. Second molars are in almost all situations inaccessible from palatal due to anatomical risks. The greater palatine foramen is located approximately 3-4 mm anterior to the posterior border of the hard palate, with nerve and blood vessels running in an anterior direction in the submucosa approximately midway between midline of palate and gingival margin. Soft tissue elevation for surgery on the palatal root of a first molar may include the neurovascular bundle within the flap, but any posterior access to attempt surgery on a second molar may involve the foramen with danger to the bundle and greatly increased risk of severe hemorrhage or nerve injury. As a precaution, a relieving incision for a palatal flap should be placed between the canine and the first premolar [95, 96]. Transantral surgery to reach palatal roots has been described [8, 275], but is practically often limited to root fusions of distobuccal and palatal roots, as correct root-end preparation and root-end filling is greatly complicated by the distance to the palatal apex from the buccal approach and the risk of leaving dentinal shavings and foreign body materials in the sinus.
Mental and Inferior Alveolar Neurovascular Bundles
Radiographic assessment and/or CBCT imaging and careful treatment planning are prerequisites for endodontic surgery in the mandibular premolar and molar area [108, 109, 162, 223, 267]. The mental fora- men is most frequently located near the apex of the second mandibular premolar, less frequently near the apices of the first molar or the first premolar. The distance of the mental foramen from the closest root may range from 0.3-9.8 mm [10]. Less frequently, its location was reported to be at the same level or even coronal to the apices of adjacent teeth, or present with a secondary foramen [1, 174]. The mandibular canal is located inferior and lingual to the root apices of mandibular molars. In most situations the canal is at a safe distance from the root tips of first molars. However, its proximity to the apices of the second molars, together with their posterior location and the thickness of the bone in the area of the ramus commonly prohibits surgery on these teeth.
To protect the mental foramen from damage during mandibular posterior surgery, an intra-sulcular incision should be chosen for better overview, with a vertical incision mesial of the first premolar for surgical procedures of both second premolar and first molar. To protect the mental nerve from damage, the placement of a bony groove using a surgical bur or a piezoelectric device for safe anchorage of the surgical retractors has been advocated to prevent tissue damage by accidental slippage [1] (Figure 12.5a-c).
12.8 Clinical Steps in Root-end Surgery
12.8.1 Apical Curettage
Apical curettage involves the removal of the soft tissue lesion of the apical periodontitis around the root tip without root-end resection or root-end filling [144]. While the excision of the inflammatory tissues is an integral part of root-end surgery, there are limited indications for traditional apical curettage as a self-sufficient procedure. Procedures where no resection or root-end filling will be rendered may include exploratory procedures that identify vertical root fractures or other reasons why a tooth is deemed non-restorable. Failed endodontic cases, particularly after non-surgical retreatment, that are treatment planned for a surgical procedure, should receive treatment that addresses potential intraradicular, as well as extraradicular causes for failure. Thus, other than for crown or root resection procedures, root-end resection and root-end filling should be included in the procedure to maximize the prognosis. While granulomas or abscesses should heal after the etiology of a failed endodontic treatment has been addressed, it cannot be determined during the surgical procedure whether an extraradicular infection is present. Thus, as part of a surgical procedure, it should be attempted to remove the entire periradic- ular lesion [32, 144, 171, 206, 207], to include any epithelial remnants that might continue proliferation of a cystic lesion, or any extraradicular infection.
Figure 12.5 Intra-operative protection of mental neurovascular bundle. (a) Clinical view of mental foramen and neurovascular bundle inserting into buccal soft tissues. (b) Preparation of a groove to anchor a surgical retractor using a piezo-electric device. (c) Safe placement of retractors during surgical procedure on first left mandibular molar in groove protecting the mental nerve. Note epinephrine containing cotton pellet improving hemostasis in mesial osteotomy during ultrasonic root-end preparation of distal root. Courtesy of Dr Frank Setzer, Philadelphia, PA, USA.
12.8.2 Root-end Resection
After inflammatory tissues have been removed from the periradicular area, the root apex should be clearly identifiable. Root-end resection will remove the anatomical complexities that may harbor intraradicular infection: apical ramifications, accessory canals, or severe apical curvatures; iatrogenic mishaps that prevented access to the entire root canal system throughout non-surgical retreatment, including perforations, ledges, transportations, or foreign body materials; apical root fractures or cracks; or apical resorptions that prevented an adequate seal during the conventional procedure. The root-end resection will also aid in removing etiological factors in the tissues, such as foreign bodies and extraradicular infections. Resection of the root apex should be performed with a fissure bur or a Lindemann bone cutting bur, to achieve a smooth resected root surface that permits the inspection of the internal root anatomy, thereby allowing for the identification of potential reasons for the failure of the previous treatment. No consensus exists in the literature how much apical root structure should be resected. However, resection to the base of the lesion [37] is regarded unnecessary [95, 96]. As much buccal bone as possible should be preserved. The apical foramen, as well as accessory and lateral canals are the major physiological pathways for intraradicular infection to reach the periradicular tissues. Bacteria will be able to penetrate dentinal tubules, but may not reach periodontal tissues across an intact cementum layer. Microorganisms in dentinal tubules exposed to the periradicular tissues by the root resection were discussed as a potential source of infection in the surrounding tissues after surgical endodontics. Never- theless, a correlation between the presence of microorganisms in the dentinal tubules and the degree of periradicular inflammation could not be demonstrated [206]. A minimally beveled resection angle aids in keeping the number of open dentinal tubules after resection at a minimum. In addition, root-end preparation will also greatly reduce the numbers of bacteria in the dentinal tubules, as the majority of bacteria in the apical third have been shown to be located immediately adjacent to the root canal system [117, 225].
Based on an anatomical study, three mm of root-end resection eliminated 98% of apical ramifications and 93% of lateral canals [125], and can aid as a clinical guideline. This amount may vary depending on individual situations, for example, it may be more in the proximity of anatomical structures such as the mental nerve or to remove a fracture line, or less, if only limited root structure is available apical of a post. The root should be a resected at a shallow 0-10° bevel, rather than a traditional steep 45° bevel [42, 125, 206], in order to preserve apical root structure; decrease the chance of missing lingual and accessory canals; guarantee complete root resection; expose less dentinal tubules that may aid in spreading intraradicular infection [51, 85, 97, 245]; and allow for an easier co-axial root-end preparation with ultrasonic tools.
The inspection of the resected root surface is done after complete hemostasis is achieved. After rinsing the osteotomy site with saline, still existing bleeding spots may be stopped by using cotton-pellets soaked with epinephrine or hemostatic agents such as ferric sulfate or aluminum chloride. All hemostatic agents will have to be removed by the end of the surgical procedure, to clear away any toxic components that might have potentially adverse effects on healing [98, 110, 114, 141], and allow the osteotomy site to fill in with blood. Methylene blue or other suitable dyes is used to stain the resected root surface [125] after carefully drying it with a micro irrigator, such as the Stropko device [237]. This procedure will not only outline the circumference of the periodontal ligament to ensure complete resection, but aid in identifying missed canals, microfractures, isthmuses - narrow connections between main canals, often harboring tissue remnants and infection - other anatomical details, aberrations, or iatrogenic errors (Figure 12.6a). The inspection of the resected root surface should be undertaken at high magnification (16-24x) [272]. At a 3-mm resection level from the original apex, isthmuses were found at 90% of the mesio-buccal roots of maxillary first molars, 30% of the maxillary and mandibular premolars, and over 80% of the mesial roots of the mandibular first molars [107, 279] (Figure 12.7).
Figure 12.6 Clinical steps of resected root inspection, root-end preparation and root-end filling of a first left mandibular premolar. (a) Micro-mirror view of resected root surface after staining with methylene blue. Note buccal canal with existing root filling [B], missed lingual canal [L] (circle), and isthmus [I] (arrow) connecting buccal and lingual canals. (b) Root-end cavity, including isthmus preparation. (c) Root-end filling in situ (MTA). Courtesy of Dr Frank Setzer, Philadelphia, PA, USA.
Figure 12.7 Axialp-CT view of mesial and distal roots of a first mandibular molar. Isthmus [I] (arrow) connecting mesiobuccal canal [MB] and mesiolingual canals [ML]. Note calcification [C] in distal canal. Courtesy of Dr Vanessa Cabrera Saez, Philadelphia, PA, USA.
12.8.3 Root-end Preparation
Root-end preparation aims at cleaning portions of the root canal system that have been left untouched by previous conventional root canal therapy. This may include previously non-negotiated canals and situations where the quality of the existing root filling is unsatisfactory, either due to insufficiency of the sealer to fill all gaps between the core filling material and the root canal wall or to anastomoses between canals. Even fine isthmuses between canals should be instrumented during root-end preparation [153] (Figure 12.6b).
Root-end preparation is done with ultrasonic tips. Prior to cavity preparation, the operator should align the ultrasonic tip in the direction of the long axis of the root at low magnification (4x-8x) (Figure 12.5b). Special tips with variations in angulations exist for different areas of the jaw. While there have been concerns about cracks in the root after ultrasonic root-end preparation [75, 140], these seem not to be relevant for the clinical outcome [19, 122]. Smaller or larger tips may be used dependent on the original shape and size of the root canal. Prior to root-end filling, the cavity should be dried and inspected at high magnification using a micro-mirror to verify that all filling remnants in the cavity have been removed completely, particularly in the buccal aspect, as this part of the root canal wall cannot be directly observed during ultra- sonic preparation [237].
12.8.4 Need for Root-end Preparation
A number of properties may be attributed to an ideal root-end filling material. Biocompatibility and sealing ability are of primary importance; also. bactericidal or bacteriostatic activity is conducive to the overall purpose of treatment. In addition, technical properties support these basic functions: adhesion to the root canal surface; dimensional stability; non-corrosiveness; resistance to dissolution; ease of manipulation with an adequate working time; non-staining of teeth or tissues; osteoand cementogenic properties; and radiopacity.
A wide range of root-end filing materials have been proposed, investigated, and reviewed [50, 118, 253]. Materials that have been widely used, also in clinical studies, include amalgam, gutta-percha [173, 186], zinc oxide/calcium sulfate cements (Cavit) [73, 172, 187], polyvinyl resin (Diaket) [244], glass-ionomer cements [116], composite resin (Geristore, Retroplast) [9], zinc oxide/ eugenol cement (IRM, SuperEBA) [101], and calcium silicate cements (mineral trioxide aggregate (MTA), biodentine, bioceramic root repair material (BC, RRM). With the exception of amalgam, which was included due to its historical importance and that it is still being used by some practitioners [33], only the most contemporary root-end filling materials are discussed in detail.
12.8.5 Root-end Filling Amalgam
Amalgam was the most popular and widely used root-end filling material for many years [26, 77, 273]. Amalgam has been criticized for its lack of biocompatibility, corrosion, risk of crack formation in the root apex, hard tissue staining and soft tissue tattoos due to silver salts [100], and poor performance in regard to outcome [7, 63, 73, 116, 178, 221] (Figure 12.8a-e). Amalgam has been demonstrated to leak under in vitro conditions based on dye penetration tests [77, 177], or the the fluid filtration model [234, 282]. While it was criticized that this were not in vivo conditions [188, 201], amalgam also showed bacterial leakage [53, 255], and consistently allowed for greater leakage than any other material under review, independent from the methods [53]. Hence, it is likely that amalgam allows for leakage as a root-end filling material [13, 53, 96]. Amalgam's lack of biocompatibility derives from its mercury content, which has been described as an environmental hazard, and attached great scrutiny for its use as a restorative filling material [66]. Histologically, amalgam or its corrosion products have been considered responsible for unfavorable inflammatory tissue responses [16, 51, 188, 252, 256], with traces of amalgam still detect- able from the root end [188]. Periapical tissue inflammation was shown to be most severe and extensive among all materials compared [51, 188, 192, 252, 254].
Composite Resin
Good sealing ability of composite resin in a root-end cavity has been demonstrated in in vitro studies [3, 150, 151], and Geristore, a dual- curing hydrophilic modified composite resin, has been used as a material for conventional root-end filling, and for the repair of subgingi- val or subosseous defects, and as a barrier material for guided tissue regeneration (GTR).
A different technique to seal the resected root apex by composite resin materials was first introduced by Rud et al. in 1991 [209], and more recently used by von Arx et al [268]. While using high magnification of a micro- scope or an endoscope, the technique differs significantly from other traditional or con- temporary approaches, as no conventional root-end preparation and root-end filling is done. Instead, a round bur is used to create a concave cavity over the entire resected root surface, which is then etched with EDTA, and a bonded resin material is placed in a domelike fashion. The materials used with this technique is Retroplast, a dentine-bonded dual-curing composite resin [209, 268]. While the technique has demonstrated favorable results compared to traditional root-end surgery techniques [115, 209, 210, 211], it is less effective compared to contemporary techniques [130], and indications restricted to situations where an ultrasonically prepared root-end cavity cannot be prepared. The technique's major drawback is its dependency on excellent moisture control, as otherwise the filling material will not stay connected to the resected root surface [210, 211].
Figure 12.8 Surgical treatment in left maxillary quadrant. Apical periodontitis on second premolar and buccal roots of first molar (verified by CBCT). History of traditional root-end surgery using amalgam retrograde filling in mesiobuccal root of first molar. Buccal swelling and symptoms originating from overextended amalgam filling mesial of second molar. (a) Preoperative radiograph. (b) Clinical view of existing amalgam retrograde filling. (c) New root-end filling in situ (RRM). (d) Postoperative radiograph with root-end fillings on premolar and molar in situ. Situation after re-contouring of existing amalgam filling on second molar. (e) 12-months follow-up radiograph. Radiographic healing observed, no clinical symptoms. Note endodontic treatment and new coronal restoration on first premolar. Courtesy of Dr Frank Setzer, Philadelphia, PA, USA.
Zinc Oxide/Eugenol
Zinc oxide/eugenol (ZOE) cements were recommended for many decades [81, 171] as materials to be used in root-end surgery. The two most commonly used materials are intermediate restorative material (IRM), a ZOE cement reinforced by the addition of polymethacrylate to the powder, and super ethoxybenzoic acid (SuperEBA), modified by the partial substitution of eugenol liquid for orthoethoxybenzoic acid and the addition of fused quartz or aluminum oxide (alumina) to the powder. Both materials demonstrated a significantly better outcome than amalgam [63, 204, 205], and histologically proved to be more biocompatible than unmodified ZOE, although there was still presence of some inflammatory cells on the root surface [188, 191, 192]. Both IRM and SuperEBA exhibit low solubility [48], good antibacterial action [49, 251], and little leakage in dye penetration tests [47, 175]. SuperEBA allows for significantly less leakage and better root wall adaptation compared to amalgam. Studies that used either IRM or SuperEBA as root-end filling materials, use ultrasonics for root-end preparation and employ the use of high magnification commonly qualify for inclusion in meta-analysis evaluating the outcome of Endodontics microsurgery [130, 220, 221].
Calcium Silicate Cements
Originally deriving from Portland cement, a silica, alumina and calcium compound con- struction material, a variety of dental filling and repair materials have been developed, including mineral trioxide aggregate (MTA), BioDentine, or Bioceramic root repair material (BC, RRM). All materials are hydrophilic, but vary in setting time and methods of preparation. The calcium silicate cements offer significant improvement over zinc oxide/ eugenol cements, showing reduced cytotoxicity [29, 55], increased biocompatibility [84, 158], increased cell attachment [55], cemento-, and osteoinductive properties [46, 84], as well as increased pH values [88].
MTA was the first material introduced [252] and has been comprehensively investi- gated. Several histological studies of root-end fillings in animals [16, 197, 252, 254] have shown that MTA demonstrate considerably less inflammation than amalgam, and allows new cementum to form over the resected root surface (Figure 12.9) and the root-end filling itself [252, 254] (Figure 12.10a-b). Recent investigations have demonstrated the formation of a hydoxyapatite (HA) layer on the MTA surface in contact with tissue fluid during setting of the material, described as “biomineralization” [25]. It was suggested that this layer creates a biologic seal between MTA and the dentin interface and thus enhances the long-term sealing ability of MTA. Disadvantages of MTA included its handling properties and a potential for tooth discoloration, for both its gray and white formulations [131]. Prepared MTA has the consistency of a moist, granular paste, and it may be difficult to place it in a root-end cavity. MTA may also be prone to washout effects in the presence or excessive bleeding or other tissue fluids compromising its sealing ability.
Figure 12.9 Deposition of new cementum [C] layer on resected dentin [D]. Note absence of inflammation, proximity of bone [B], and periodontal ligament structures [PDL]. Modified from [45].
Figure 12.10 Histologic representation of root and periapical area after placement of MTA root-end filling. (a) Section of root with root-end filling [MTA]. (b) Close-up of marked area in 12.10a. Newly deposited, mineralized cellular cementum [C] growing over MTA. Modified from Baek et al. [16].
The newer formulations of calcium silicate cements, BioDentine, a capsule-based material to be mixed in a triturator, and the premixed RRM alleviated some of the problems encountered with MTA. Both materials exhibited less tooth discoloration effects than MTA [131], RRM has received more attention as a root-end filling material than BioDentine, which is more often used for perforation repair. RRM is dimensionally stable, demonstrates a high pH, and needs as short as 2 hours of setting time. No significant differences were demonstrated between RRM and MTA in regard to their antimicrobial efficacy [146], biocompatibility [5], and sealing ability [166]. In an in vivo study comparing RRM and MTA as a root-end filling materials [45], no or minimal inflammation was evident at the surgical site upon healing, with cementum-like tissues observed adjacent to RRM, comparable to previous findings for MTA (Figure 12.11a-b). Two randomized controlled trials investigating endodontic microsurgery have demonstrated highly favorable outcomes [224, 285].
12.8.6 Wound Closure and Postoperative Care
Once a surgical procedure has been completed, wound closure and postoperative care will determine a great part of the biologic and esthetic healing process. The osteotomy site should be inspected and cleaned of any excess materials and hemostatic agents to avoid foreign body reactions and to remove any toxic byproducts from materials such as ferric sulfate. Blood should be allowed to fill back into the osteotomy site, to allow for the formation of a blood clot and the subsequent osseous healing. Any grafting material or membrane should be placed at this stage of the procedure. The soft tissue is moistened with a wet gauze containing saline before flap repositioning, as the soft tissue may have become dehydrated during the surgical procedure and rehydration will aid in regaining the tissues' natural elasticity. Soft tissue management may have a great impact on the esthetic results. Sutures will be necessary to place the mucoperiostal flap back into its original position. Accuracy will be increased by using a microscope or loupes, in particular for smaller suture diameters. Common sizes are 5-0 or 6-0 for standard interventions, in esthetically demanding areas, such as the anterior maxilla, or if a papilla base flap was chosen, 7-0 sutures may be advised for repositioning of the papillae. For any flap design, close contact to the underlying bone needs to be established to minimize the thickness of the subperiostal blood clot and allow for healing by primary intention.
Figure 12.11 Histologic representation of root and periapical area after placement of RRM root-end filling. (a) Section of root with root-end filling [RRM]. (b) Close-up of marked area in (a). Mineralized tissue formation on surface of RRM. Note periodontal ligament structure [PDL] and proximity of bone.
Modified from [45].
Nylon, polypropylene, or polytetrafluoroethylene (PTFE) monofilament or coated mono- filament sutures have become the material of choice [265], as traditional silk sutures may promote bacterial colonization and impede wound healing. Resorbable sutures, such as gut, reduce the number of office visits, but add an inflammatory component to the wound healing process by their resorption. The need for suture removal will also allow the clinician to check on the patient 48 hrs [96] to 4 days [95, 263] days after the surgical intervention and have a close control of the healing process. It was reported that if sutures were left too long some flap margins may be compromised by infection [91, 96]. Needle shape, size, and curvature are important for the particular procedure, but its selection may vary with the periodontal biotype, access to the area, and preference of the operator [265]. Single interrupted sutures are generally preferred over continuous sutures as they allow for a more controlled readaptation. A sling suture may be used for interproximal readaptation in the posterior areas. The patient should be instructed on the first 1-2 days to avoid exercise and not to pull up his or her lips, which could precipi- tate bleeding or open up flap margins, which may pose a risk of infection to the underlying blood clot with associated pain and swelling, and delayed healing. The patient should refrain from smoking as long as possible, and for several days only have food that can easily be removed from the surgical site by regular dental cleaning. Interval cooling with an icepack will prevent excessive swelling [94, 96]. The patient should also be informed that besides swelling and pain, temporary discol- oration and bruising may occur in a small number of patients. If the patient can tolerate NSAIDs, this type of analgesics should be the first choice, as it is anti-inflammatory and analgesic. Antibiotic coverage is not generally advised [94], but may be indicated based on the patient's medical or dental history. Careful rinsing with a chlorhexidine solution after the first day will be beneficial to the wound healing process, as it reduces bacterial content in the oral cavity and thus minimizes the risk of postoperative infection of the surgical site. The patient should receive contact information for after hour emergency assistance. Lastly, the patient should be instructed that he/she should return in the event of any recurrent symptoms after the initial healing phase. The patient should return after 4 weeks for a follow-up to ensure successful soft tissue healing, and the absence of any clinical symptoms, and after 1, 2, and 4 years to radiographically monitor the healing process and ensure that the long-term success is guaranteed after several years.
12.9 Perforation Repair
A perforation is an abnormal communication between the pulpal space and the periradic- ular tissues [198]. Perforations usually occur iatrogenically through access perforation, incorrect instrumentation, post preparations, or aggressive canal enlargement. Less frequently, perforations occur when correct treatment creates communication with resorptive or carious defects. Locations for perforations may vary from the gingival sulcus to subcrestal, mid-root or apical parts of the root. Successful perforation repair depends primarily on whether the perforation site harbors infection, and on the size of the defect, access and visualization to facilitate repair. Immediate perforation repair has a better prognosis than the repair of a perforation that has allowed microorganisms to invade the perforation area, with inflammation and severe bleeding compromising repair [170, 216]. Perforation within the gingival sulcus can be repaired by a conventional restoration, or by raising a small flap to have good control over the margins of the restoration. Depending on moisture control, a bonded composite resin or a modified composite resin are the materials of choice. Subcrestal repairs may be subject to non-surgical repair from inside the root canal system [198] or to surgical repair if they are out of reach of application syringes or micropluggers; if they cannot be visualized because they are located beyond a curvature; or if bleeding from periradicular tissues cannot be controlled. The ideal properties of a subcr- estal repair material are essentially identical with those put forward for root-end filling materials. The formation of cementum or cement-like tissues over materials such as MTA [193, 254] or RRM [45] make calcium silicate cements suitable materials [198, 248]. Most perforations do not require surgical repair [20, 24, 137]. If a surgical repair is indicated, protocols will generally follow those described for root-end surgery, with the modification that the resection needs to include the perforation area. In situations where the crown-to-root ratio may be compromised, a deviation from a near perpen- dicular resection angle may be indicated to allow for more periodontal support from the remaining root structure.
12.10 Replantation
Intentional replantation is the purposeful removal of a tooth and its almost immediate replacement after root-end preparation and root-end filling extraorally prior to reimplan- tation [90]. It is not considered the first choice of retreatment [278], however, where a non-surgical retreatment option cannot be performed for restorative or endodontic reasons, or if this option was already exhausted, and a regular surgical retreatment approach cannot be facilitated due to anatomical limitations, intentional replantation may be performed to avoid tooth extraction [2, 68, 89, 133]. An updated review and meta-analysis including studies from 1966-2014 demon- strated an 88% survival rate for teeth following intentional replantation, and an 11% incidence rate for root resorption following treatment [247]. A protocol will include a slow and careful extraction of the tooth to avoid fractures; loss of the coronal restoration; and damage to the alveolar bone, the periodontal ligament in the socket, and the cementum layer (Figure 12.12a-f). Curettage of the socket walls should be avoided in order to allow for re-establishment of the periodontal ligament. After the tooth has been extracted, great care must be taken not to touch the root surface to prevent periodontal tissue damage and root resorption [12, 121]. For the same reason, scaling and root planing of the replanted tooth is contraindicated. Some surface resorption inevitably takes place shortly after replantation peaking after 2-4 weeks, but this is transient and dimin- ishes after approximately 2 months. During the extraoral phase, the tooth must be care- fully inspected for fractures or any other iatrogenic damage during the extraction, and to identify possible reasons for failure of the prior endodontic treatment. In deviation from the standard protocol, root-end preparation may be performed with a thin fissure bur, since there are no space restrictions that would necessitate the use of an ultrasonic tip. The extraoral time should not exceed 15 minutes [129] in order to avoid degeneration of the periodontal ligament structures on the root surface. Irrigation of the tooth with an isotonic salt solution should be carried out frequently, so that drying out does not occur [86]. Upon reimplantation, care must be taken to place the tooth in the correct orientation, preferably in slight infra- occlusion, since the tooth has been resected.
If the tooth is slightly out of occlusion during the healing phase, a better re-attachment of the PDL may occur, as occlusal forces are minimized. The mobility of a replanted tooth should be kept at a minimum; however, splinting is only needed in situations with increased mobility. The patient should be advised to avoid chewing on the extracted tooth for at least two weeks postoperatively. Regular follow-up according to the protocol for endodontic surgery is indicated.
12.11 Root Amputation, Hemisection
Root amputation procedures were first mentioned in the 1880s for treatment of multi- rooted teeth with furcation involvement [71]. Root amputation is considered a “root resection” technique as it only involves the removal of root structure below or at the level of the cemento-enamel junction without removal of portions of the crown [222]. In contrast “crown resection” includes hemisection, trisection, and premolarization (bicuspidization), i.e., all procedures where a dissection transverses through the furcation and the crown of a multi-rooted tooth so that a root and the associated portion of the crown may be removed (hemisection, trisection) or all root/ crown section are being retained (premolari- zation, bicuspidization) [222]. Indications and contraindications for crown and root resection include the following [159, 222, 235]: Indications:
• severe bone loss affecting one root, not amenable to other forms of therapy
• moderate to advanced furcation involvement with divergent roots
• unfavorable root proximity between adjacent teeth
• root fracture, perforation, root caries, or external root resorption involving one root or the furcation area
• endodontic treatment of a particular root canal cannot be performed, and root-end surgery is contraindicated
• a tooth, which is an abutment of a bridge, can be retained after removal of a particular root
• when anatomical situations preclude implant placement.
Figure 12.12 Treatment of second right maxillary molar by intentional replantation. History of unsuccessful non-surgical retreatment with presence of clinical symptoms. (a) Preoperative radiograph. (b) Irrigation of the extracted tooth with an isotonic salt solution. (c) Resected root surface after staining with methylene blue. Note long oval canal cross-section with unfilled canal portions. (d) Root-end filling with RRM. (e) Postoperative radiograph. (f) 18-months follow-up, radiographic healing observed, no clinical symptoms. Courtesy of Dr Bekir Karabucak, Philadelphia, PA, USA.
Contraindications:
• insufficient bone support around the remaining roots or in the furcation area
• the furcation is too close to the apex, not sufficiently separated, or roots are fused
• it is impossible to perform endodontic treatment in the remaining roots, unfavorable anatomy of the remaining roots
• extensive caries or root resorption in the furcation area
• minimal strategic value of the remaining root structures.
Proper endodontic treatment should be done prior to the surgical procedure [159]. If the resection requires cutting through metal restorations or involves the removal of considerable amounts of coronal tooth structure, this should be carried out prior to incision and reflection of the flap to prevent tooth particles and metallic fragments to be left behind in the soft tissues. Surgical access should be provided by buccal and lingual full-thickness muco-periosteal flaps to allow for sufficient access and visualization for the completion of the resection and proper wound closure. Inflammatory tissue must be removed, and the root to be removed dis- sected from the main trunk of the tooth by a long fissure bur or Lindemann bone-cutting bur. Full separation should be checked by using a periodontal probe carefully probing through the furcation area and by testing the mobility of each root individually. Once a root is cleanly separated, it can be carefully removed avoiding damage to the remaining tooth structure. The remaining coronal structure is contoured to ensure that no overhanging tooth structure remains, which could be plaque-retentive. The root surfaces should be cleaned, all granulation tissue removed, and and osteoplasty performed for the remaining bone, to eliminate any irregular contours and provide a biologic width for the dentogingival complex after healing. The flap should then be repositioned and sutured. Follow-up instructions follow the same guidelines as for root-end surgery. The permanent restoration should allow the patient good hygiene access. There have been a number of clinical studies [21, 38, 40, 41, 61, 69, 80, 99, 106, 139, 180, 241, 284], and a systematic review and meta-analysis on the outcome of root resection, discussed in detail below [222].
12.12 Guided Tissue Regeneration
Guided tissue regeneration (GTR), or the use of bone grafting materials and/or membranes, has been used extensively in periodontology and implant dentistry, but much less so in endodontics [259]. Membranes to separate bone healing from connective tissue healing were introduced in the 1950s, yet much later for a dentoalveolar application 1960s [30]. For endodontic surgery, membranes have been investigated in animal studies [58, 59, 149], as well as in patients [67, 185]. The placement of any grafting materials or mem- branes occurs immediately prior to wound closure at the end of the surgical procedure. Common materials include polytetrafluoroethylene (ePTFE, Goretex), collagen or poly- lactide for membranes; freeze-dried bone allografts, demineralized freeze-dried bone allograft, hydroxyapatite, tricalcium phosphate, bioglass or calcium sulfate for grafts. GTR effectively excluded epithelial ingrowth into lesions and permitted bone regeneration compared to control lesions with no barrier usage [14, 82, 266].
The application of GTR for endodontic surgery has been reviewed [143, 259]. In endodontic surgery, a distinction can be made between uncomplicated defects, complicated defects, and periodontally involved defects.
Uncomplicated defects are endodontic lesions without any periodontal component,
such as deep probings on the tooth, or even a connection between periodontal and endodontic defects. No differences were seen in the healing rate with or without membrane placement [83, 149] or the placement of membrane combined with a graft at a 1 year recall follow-up [243]. Similarly, no differences were observed in periapical bone healing and bone density using CT scans after a 6-month follow-up [212].
Complicated defects are also endodontic lesions without any periodontal component; however the defect exceeds 10 mm in diameter, presents with a bucco-lingual “through and through" defect, and/or perforation to the nasal cavity, or a large perforation to the maxillary sinus. These lesions may benefit from GTR techniques. Buccal and lingual membrane placement in “through and through" rat calvaria defects showed complete healing versus no healing without membranes in the control group [66]. In similar defects, membrane placement showed complete healing after endodontic surgery of cases where a barrier was utilized versus controls that demonstrated only fibrous connective tissue [57, 58]. In humans, healing of through and through lesions was 88% with GTR placement versus 57% without [242]. These findings indicate that through and through lesions should have buccal and lingual barriers to heal effectively [27]. Lesions sizes that exceeded 10 mm in diameter demon- strated faster healing and better outcome when GTR techniques were utilized versus without [184, 185], including clinical, radiographic, and histologic results [185, 196, 246].
Periodontally involved defects present with bone loss in the furcation, apico-marginal or perio-endo communication defects, or a loss of the buccal plate due to a dehiscence or completely denuded root. The overall success rate of endodontic surgery has been shown to be significantly decreased for periodontally involved defects compared to endodontic lesions alone [124, 233]. The usefulness of GTR to improve the periodontal status of a tooth has been demonstrated by histologic and clinical outcome studies. Membrane placement in situations with buccal plate loss in dogs significantly increased the amount of alveolar bone regenerated [65], and membrane placement plus a graft may significantly increase cementum deposition [31, 60].
In conclusion, GTR techniques appear beneficial in situations of complicated and periodontally involved defects.
12.13 Retreatment of Failed Surgical Cases
The most common cause of failure of the initial surgical procedure is the absence or incorrect placement of a root-end filling [133]. A long-term follow-up of cases that were deemed successful at short-term followup identified long-term failures to be mostly related to operator mistakes [232]. If the cause of failure is an insufficient root filling, coronal leakage is detected, and the root canal system is accessible and negotiable, non-surgical retreatment should be the first choice of treatment [231]. Non-surgical retreatment after failed endodontic surgery was evaluated by Mente et al. [157]. In this prospective case series, orthograde retreatment and filling with an apical MTA plug was performed in 25 cases, with an overall success rate of 87%. However, the success for anterior teeth was 100% compared to 80% for posterior teeth, highlighting the increased difficulties and challenges associated with this procedure on multi-rooted teeth [157]. If non-surgical retreatment is not the preferred or most predictable option, re-surgery, or extraction should be considered [207]. If fail- ure is associated with one particular root, crown or root resection may be an option to save the tooth [222]. Some studies reported that re-surgery had a very poor prognosis, and might often be contraindicated [215, 270], and a systematic review of endodontic re-surgery, reported a weighted pooled success rate of only 36%, albeit including traditional techniques for the secondary surgical procedure [190]. If microsurgical techniques and biocompatible root-end filling materials such as MTA and Super-EBA were used, a much higher success rate for endodontic re-surgery may be achieved, approaching those of first-time surgery [231].
12.14 Modes of Healing
Healing of the periapical tissues requires recruitment of stem/progenitor cells from the bone marrow, endosteum, periosteum, and the periodontal ligament to differentiate into osteoblasts, PDL cells, and cementoblasts. Healing of the excisional wound after surgery takes place faster than the regression of a granuloma or cyst after non-surgical treatment, where the inflamed tissues must first be degraded by phagocytic debridement [143]. After endodontic surgery, the bony defect is filled with blood, and the blood clot will be protected from infection from the oral cavity by the repositioned flap. Epithelial cells will proliferate to close the wound from the surgical incision. Antiseptic solutions are recom- mended for the patient during the first week after the surgery to reduce the risk of infection of the surgical site. Below the soft tissues, healing takes place as two separate processes, osseous healing and dentoalveolar healing.
12.14.1 Osseous Healing
Osseous healing after surgical intervention will require hemostasis, by vasoconstriction and platelet aggregation [143]. There are three basic phases of wound healing, with consider- able overlap between the stages: inflammation, proliferation, and remodeling [54, 60, 135, 152, 281]. Within these three phases a complex and coordinated series of events occurs. The inflammatory phase includes chemotaxis and phagocytosis [135, 152]. In the proliferation phase neocollagenesis, epithelialization, and angiogenesis result in the formation of granulation tissue originating from the PDL and endosteum [52, 102, 135, 152]. Lastly, in the remodeling phase, active collagen remodeling and tissue maturation take place, which either results in repair or regeneration [135]. For the osseous wound, this translates into the revas- cularization of the initial blood clot and the formation of a mineralizing matrix, which from woven bone eventually matures into cancellous bone. New bone formation starts in the internal area and progresses externally towards the level of the former cortical plate. As newly laid woven bone reaches the lamina propria, the overlying membrane becomes functional periodontium, which is part of the osseous healing process. This is separate from dentoalveolar healing, as it occurs as a response to the surgical excision.
12.14.2 Dentoalveolar Healing
During the development of apical periodontitis, periodontal ligament, cementum and dentin were resorbed at the root apex. Viable periodontal ligament (PDL) cells from the adjacent root surface proliferate during the dentoalveolar healing process and cover the denuded root surface [143, 145]. From these tissues PDL stem cells will differentiate into cementoblast-like cells, allowing cementum to regenerate [143, 145]. Root resorption that involved both cementum and dentin can only be repaired by cementoid tissue, because PDL stem cells are unable to differentiate into dentin producing osteoblasts [217]. In the absence of infection or severe inflammatory reactions, cementum has been shown to grow back to cover the resected dentin surface [11, 13, 102, 202]. MTA and RRM both allow cementum apposition directly on the material surfaces [45, 252, 254]. In addition, MTA may support the re-establishment of a PDL width comparable to its natural thick- ness, whereas the bone-to-material distance was twice that for SuperEBA and four times as large for amalgam [15].
12.15 Outcome of Surgical Endodontics
Just as for non-surgical endodontics, the purpose of endodontic surgery is the elimination of apical periodontitis and prevention of its recurrence. The most widely used classification to assess the outcome of endodontic surgery is based on the criteria by Rud and Molven [161, 208]. Success is defined radi- ographically as complete healing or incomplete (scar tissue formation) healing and clinically by the absence of pain, swelling, percussion sensitivity, or a sinus tract (Figure 12.13a-d). Failure included the radiographic categories of uncertain healing (reduced lesion size) or unsatisfactory healing (unchanged or increased lesion size) and clinically the presence of any of the symptoms mentioned above. According to Molven et al. [161] postoperative healing-related changes mostly occur within the first year after the surgical intervention. Asymptomatic cases with complete or incomplete healing are then considered success, whereas situations with uncertain healing should be re-evaluated for up to 4 years and then designated as success or failure. Survival of the tooth has been validated as the positive outcome measure for resective therapies [222]. Criteria for 3-dimensional assessment of periapical healing after endodontic surgery have recently been introduced [45, 214] and validated [269] (Figure 12.14a-f). The majority of studies evaluating the outcome of surgical procedures have, however, relied on clinical evaluation and 2-dimensional radiographic interpretation.
Figure 12.13 Outcome evaluation using conventional 2-dimensional radiography after surgery on mesial root of a first right mandibular molar. (a) Preoperative radiograph. (b) Postoperative radiograph. Note isthmus preparation and root-end filling in situ (RRM). (c) 12-months follow-up, radiographic healing observed, no clinical symptoms. (d) Close-up of marked area in (c). Note radiographic re-establishment of periodontal ligament outline and osseous healing in the periradicular area. Courtesy of Dr Frank Setzer, Philadelphia, PA, USA.
Figure 12.14 Outcome evaluation comparing conventional 2-dimensional radiography with 3-dimensional CBCT imaging after surgery on mesial root of a first right mandibular molar. (a) Preoperative radiograph prior to non-surgical retreatment. (b) Postoperative radiograph after retreatment. Note that the mesial root canal system could not be negotiated. Presence of clinical symptoms. (c) Preoperative 3-dimensional segmentation of periapical lesions. (d) Postoperative radiograph after surgical procedure with mesial root-end filling (MTA). (e) 18-months follow-up radiograph. Radiographic healing observed, no clinical symptoms. (f) Three- dimensional segmentation of remnant low density areas identified in CBCT image, allowing for volumetric comparison and more precise assessment of periapical areas (follow-up CBCT imaging approved by institutional review board). Courtesy of Dr Tom Schloss, Nuremberg, Germany.
A systematic review of studies investigating the outcome of surgical endodontics found success rates ranging from 37% to 91%, varying with the operator and the specific techniques used for the surgical procedures, and including all historic techniques [78]. The evaluation of outcome has to be undertaken cautiously, however, since there are many variables in treatment protocol and methodology between different studies, including study design, sample sizes, inclusion and exclusion criteria, follow-up periods, lack of standardized clinical and radiographic parameters for healing, the periodontal condition of the teeth prior to surgery, variations in the quality of previous endodontic treatment, the coronal restoration, and the surgical materials and techniques itself. Moreover, many studies reporting the success and failure of periradicular surgery were case series or other studies with a low level of evidence [154]. However, as it has been demonstrated that results of well-designed observational studies, cohort or case-control designs do not systematically overestimate the magnitude of the effects of treatment as compared with those in randomized controlled trials on the same topic [56], results from systematic reviews and meta-analyses assessing the best available evidence should be considered valid.
Few dental techniques have undergone such a substantial evolution as root-end surgery. A number of systematic reviews and meta- analyses have documented the differences in outcome for periradicular surgery depending on the techniques used for the procedures. Traditional, now obsolete techniques using a straight surgical handpiece, a beveled root resection, and often a retrograde amalgam filling demonstrated weighted pooled success rates of 59.0% [221]. The use of loupes, ultrasonic root-end preparation, and more biocompatible filling materials increased this outcome to 86% of periapical healing [220]. Endodontic microsurgery, using the same tools and techniques, but replacing loupes with a dental operating microscope capable of providing high magnification demonstrated even higher success rates ranging from 91.4% to 94.4% for true endodontic lesions [130, 221, 250, 260]. On the other hand, a recent systematic review and meta-analysis assessed the outcome of resin-based endodontic surgery, using high magnification to preparation a shallow and concave root-end cavity and fill it with bonded resin-based root-end filling material - such as the Retroplast technique, to be successful in 82.2% of the cases, with failures likely to be attributed to bonding failure in the moist periradicular environment [130]. Bioceramic root repair material has been successfully used as an alternative to mineral trioxide aggregate with success rates ranging between 92.0-94.4% [224, 285]
A reversal of healing after periradicular surgery has often been debated. Del Fabbro et al. 2007, assessed randomized clinical trials comparing non-surgical versus surgical retreatment, and described faster healing after the surgical procedure compared to non-surgical retreatment after 1 year, but a regression of successful cases for endodontic surgery over a follow-up period of 4 years [62]. Similar assertions were stated by Friedman [79]. However, majority of healing reversals described were related to obsolete techniques, such as retrograde gutta-percha or amalgam fillings, and there is abundant data now confirming that surgical procedures with modern techniques and proper case selection do not undergo excessive failure rates, but rather minimal attrition of the population of the cases successful at follow-up. According to Song et al. in 2012 teeth that had undergone surgery using microsurgical techniques, a success rate of 93.3% was maintained for more than 6 years. Cases in the unsuccessful group were ana- lyzed during re-surgery, demonstrating that failure was predominantly associated with root fractures and operator mistakes, including missing root-end fillings, incor- rect root-end preparation, missed canals, or unaddressed and leaking isthmuses, during the initial surgery [232].
Lower outcome rates are expected, how- ever, for periodontally compromised teeth undergoing periradicular surgery, and for resective therapies. Comparing periodon- tally healthy teeth with teeth that suffered from moderate to severe bone loss undergoing surgery, the difference in success between healthy teeth of 95.2% versus a success rate of 77.5% for the periodontally compromised teeth was statistically significant [124]. Based on this study, the lowest success rates were seen for cases with probing to the apex of the root with or without complete loss of the buccal cortical plate, suggesting that careful treatment planning is indicated in these situations. A recent systematic review and meta-analysis evaluating the outcome of crown and root resection demonstrated a cumulative survival rate of 85.6%, with no statistical difference between crown resection and root resection techniques [222].
In conclusion, while endodontic surgery should be reserved for teeth with failed non-surgical retreatment, or situations where non-surgical retreatment cannot be performed for technical reasons [249], the outcome of studies utilizing modern techniques justifies its use with proper case selection.
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