Surgical Endodontics

24 Surgical Endodontics

Silvio Taschieri and and Stefano Corbella

Summary

Surgical endodontics is used for the treatment of lesions of endodontic origin when non-surgical treatment fails or is not feasible. It should always be performed after thorough presurgical planning and careful case evaluation. The scientific evidence supports the adoption of a microsurgical approach under magnification using advanced techniques for soft tissue management. Developments in biomaterials have improved healing outcomes. This chapter aims to discuss advances in endodontic micro-surgical procedures including techniques, case difficulty assessment and outcomes.

24.1 Introduction

The term “surgical endodontics” is applied to any surgical procedure directly or indirectly related to treatments and pathological conditions that may involve the root canal system. Following this definition, surgical endodontics refers to all surgical procedures to treat inflammatory diseases affecting the periapical and periradicular tissues, that are of endodontic origin, namely, to treat all inflammatory conditions whose aetiopathogenesis is related to endodontic conditions. Thus, surgical endodontics includes all the procedures associated with the surgical treatment of periapical/periradicular lesions such as treatment of external root resorption, cracked tooth, split tooth and combined endodontic-periodontal lesions, tooth resection in addition to root hemi-section, intentional tooth reimplantation, gingival margin relocation in case of endodontically compromised tooth, incision and drainage of lesions of endodontic origin (with decompression), perforation repair, root-end resection and retrograde preparation of the root-end and filling [1].

All these conditions and scenarios are associated with a range of aetiological factors, clinical features, and treatment plans. Such treatment plans are often multidisciplinary and complex, involving, in many cases, several specialties. In this chapter, the surgical treatment of lesions of endodontic origin of teeth with necrotic pulps or with root fillings where orthograde retreatment is unfeasible or has failed will be discussed.

24.2 Historical Perspective

One commonly performed procedure, from the 19th century onwards, is root-end resection and curettage of the periapical lesion, often referred to as apicoectomy or apicectomy. Historically, the first periradicular surgery procedure was described in detail in 1881 by Claude Martin. In 1884, Farrar described a technique to resect root-ends by going through the gums and the bone using a bur, while in 1886, Black provided the first indication for a surgical endodontic procedure, reporting that it was recommended in cases of long-standing “neglected” abscesses [2]. During the 20th century, surgical endodontic procedures became more sophisticated and in 1935, the first detailed description of soft tissue management during surgical endodontics was published. In the following decades, the first materials for root-end filling, such as amalgam and zinc-eugenol cements were described [2].

For many years, the state of the art was the traditional root-end surgery (TRS) approach with round burs in miniature handpieces used to create root-end preparations for the mechanical retention of amalgam root-end fillings or warm gutta-percha [3]. At the end of the 20th century, the surgical concepts related to so-called evidence-based dentistry were reported, including the definition of more modern procedures, techniques and materials that have become the current state-of-the-art in surgical endodontics.

In the 1990s a new approach that is often referred to as modern techniques (MT) incorporated the use of ultrasonic tips and more biocompatible root-end filling materials [4]. The introduction of ultrasonic retrotips in periradicular surgery has brought many advantages for root-end preparation. They enable the long axis of the canal to be followed, while preserving the integrity of the root. Apical root-end cavities may be shaped easily, safely, and with greater precision as compared to using conventional handpieces and burs [5, 6].

Endodontic microsurgery (EMS) is the most recent step in the evolution of MT, applying not only ultrasonic preparation and biocompatible filling materials but also incorporating microsurgical instruments, high-power magnification and illumination. An important advantage of this technique is the possible identification of root micro-fractures, additional canals and a better understanding of the root-end morphology, allowing more predictable and safer root-end management [7]. Thus, surgical endodontics has changed greatly in the last decade or so, which on the one hand has improved the predictability of the results, but on the other hand has made the treatment more complex and technically demanding.

24.3 Indications for Surgical Endodontics with Root-end Resection and Treatment Alternatives

When assessing whether to perform a surgical intervention, it is mandatory to carefully consider its clinical indications and the available and feasible treatment alternatives. This process is a fundamental part of treatment planning and is also necessary for obtaining the informed consent of the patient.

From the clinical point of view, in general, surgical endodontics for the treatment of periapical and periradicular disease is indicated in conditions when a nonsurgical approach is not indicated or not feasible.

The feasibility of non-surgical root canal retreatment depends on several factors, mainly on the characteristics of the previous treatments. The situations that contraindicate non-surgical root canal retreatment include:

• presence of intracanal obstructions that cannot be removed or bypassed (e.g. posts, fractured instruments, cements, complete obliteration of the root canal due to calcification, etc.);
• presence of apical periodontitis related to tooth conditions that cannot be treated by a non-surgical approach (e.g. apical fracture, apical abnormalities);
• presence of coronal restorations that must not be damaged with a nonsurgical approach and should not be removed for any reason (e.g. when the removal of the prosthesis could cause damage to the residual tooth tissue);
• in cases where it is suspected that the periapical lesion is caused by an infection of purely extra-radicular origin or in cases of true cyst, even though preoperative diagnosis of such conditions is often difficult or impossible [8, 9].

Other clinical situations may not be an absolute contraindication for non-surgical treatment but may represent a situation where non-surgical retreatment should be considered but not definitely indicated. Such situations include:

• the presence of an adequate root filling as evaluated on periapical radiographs (e.g. adequate filling of the root canal system, adequate coronal restoration);
• clinical situations when non-surgical retreatment is feasible but not recommended since it would imply a risk for tooth survival or for the success of the treatment, namely in situations where performing a non-surgical treatment would be significantly more invasive than performing surgical endodontics (e.g. when removal of a post is required but its removal would imply a significant risk of perforation or root fracture).

In general, in all cases not belonging to the above-mentioned categories, a non-surgical approach should be recommended over surgical endodontics since it would hypothetically lead to less impact on the patients’ quality of life, and has been demonstrated to be as effective as a surgical approach when evaluating long-term tooth survival [10]. In all cases where surgical endodontics is indicated, the prognosis of the tooth should be evaluated using a multidisciplinary approach. If the prognosis of a tooth is unfavourable, the option to extract the tooth and to substitute it with a prosthesis must be considered as the treatment of choice. Among the parameters to be considered to adequately evaluate tooth prognosis the following must be evaluated:

• the periodontal status (namely the amount of residual bone, the presence of periodontal pockets, tooth mobility);
• the restorative potential (the amount of residual tooth / root after root-end resection);
• the “strategic” role of the tooth in terms of aesthetics and function (if the patient has just one tooth with one periapical lesion there may be no reason to retain it, independently from the tooth-related aspects); and
• the systemic conditions of the patient that could be a relative or absolute contraindication to any surgical treatment.

24.4 Endodontic Microsurgery (EMS) Technique

24.4.1 Diagnosis

The evaluation of each case scheduled for EMS treatment begins with a thorough clinical examination. The periodontal status of the tooth must be explored using a periodontal probe to identify concomitant periodontal bone resorption that may be a sign of periodontal diseases or of root fractures. In the presence of reduced supporting bone due to resorption the extent of root-end resection should ensure sufficient bone support is preserved. The clinical examination continues with palpation, looking for swelling, provoked pain and interruptions of the cortical bone plate, and with the evaluation of tooth mobility, that could be a consequence of both periodontal bone resorption or enlargement of the periodontal ligament space by inflammation. Moreover, the presence of caries or of inadequate coronal restorations must be identified clearly before intervention since they would lead inevitably to treatment failure.

The analysis of radiographs is an integral part of case assessment. Periapical radiographic images are used to identify:

• root length and morphology;
• the characteristics of the tooth, e.g. root filling, missing anatomy, fractured files etc.;
• presence of caries and/or inadequate coronal restorations;
• the size of the periradicular lesion (apico-coronal and mesio-distal);
• the proximity (involvement) of the lesion / root apex with important anatomical structures such as the inferior alveolar nerve or maxillary sinus.

Following European Society of Endodontology [11] ESE guidelines, cone beam computed tomography (CBCT) with limited field of view is recommended in surgical endodontics when there is an indication to evaluate the proximity of anatomical landmarks and vital structures, and when the actual size of the lesion must be defined [11, 12]. Furthermore, 3-dimensional knowledge of the root and canal anatomy (such as missed canals and other anatomical features) is helpful in complex cases, when adequate settings are used [11, 12].

The application of digital innovations to the field of surgical endodontics has introduced the possibility of accurate presurgical 3-dimensional planning, that may include the production of surgical guides (analogous to what is done in implant surgery) that can be used for preparing the access through bone to the lesion and to perform root-end resection, thus reducing the size of the ostectomy [13, 14]. Such an approach could be applied in all cases in which it is mandatory to minimize the size of the bone access, for example when in proximity to important anatomical structures. Another, more recent, application of digital technology in surgical endodontics is represented by dynamic navigation systems, that provide real-time visualization of CBCT images while performing the procedure, being hopefully less invasive and more accurate during bone removal and root-end resection [15].

In general, surgical endodontics should not be performed when gingival inflammation is evident. Therefore, an emphasis on oral hygiene measures is recommended at least one week before treatment, in order to reduce local gingival inflammation. Moreover, patients should start to use an antiseptic mouthwash (chlorhexidine digluconate 0.2%) three days before surgical intervention, to reduce the risk of the surgical field becoming contaminated.

24.4.2 Anaesthesia

EMS techniques are normally performed under local anaesthesia, administered at the site of intervention or as a nerve block, using 4% Articaine or other anaesthetic solutions (e.g. Lidocaine) with epinephrine. In mandibular cases, the choice between anaesthesia using local infiltration or inferior alveolar nerve block, or both should be determined on the basis of the location, since, often, in the premolar area a nerve block can be avoided. Moreover, the differences between the efficacy of different anaesthetic solutions could vary [16]. In general, the inferior alveolar nerve block is the first option when treating mandibular molars. Anxious patients may require sedation.

24.4.3 Mucoperiosteal Flap

Several flap designs have been described in this type of surgical procedure (Table 24.1), depending on the clinical and anatomical conditions, on the size and position of the lesion and on the need to reduce gingival recession after surgery.

Table 24.1 Summary of flap design characteristics.

Flap type	Indications	Advantages	Disadvantages
Triangular flap [sulcular] (Figure 24.1a)	Few indications. For lesions in the middle / cervical region of the root	Minimal disruption of the vascular support of the flap	Low visibility; difficulty to reach the apical area
Rectangular / Trapezoidal [sulcular] (Figure 24.1b)	Most indicated. The extension depends on the extension of the lesion	Maximum visibility, even in cases of larger lesions	Possibility to cause marginal gingival recession
Paramarginal flap (Figure 24.1c)/ Semilunar flap (Figure 24.1d)	In presence of broad band of attached gingiva (some authors suggested more than 2 mm [17] of attached gingiva, but we recommend more than 4 mm)	Marginal gingival tissues not involved	Limited indications; low visibility; risk of flap necrosis; difficulties in flap repositioning and suturing

In general, in order to enhance visibility, intrasulcular flaps with one (triangular) or two (rectangular/trapezoidal) vertical incisions (Figure 24.1a, b) are recommended to allow easier flap management and to reduce bleeding at the site of intervention. One single trapezoidal flap with two vertical release incision extending at least 4 mm apical to the mucogingival junction is sufficient in cases of small lesion (5–10 mm) affecting a single tooth (Figure 24.1b). The flap could be extended in cases of lesions affecting more than one tooth. Release incisions should be avoided in the area between central incisors and between lateral and central incisor for aesthetic reasons, even though the adoption of periodontal surgical techniques could limit scar formation. Triangular flaps, with one single vertical release incision can be used, increasing the extension of the horizontal incision to guarantee sufficient flap mobility.

Figure 24.1 Illustrative drawings showing different flap designs: a, b) Intrasulcular flap with one (a) or two (b) vertical releasing incision(s). c) Paramarginal flap. d) Semilunar flap.

Paramarginal and semilunar flaps (Figure 24.1c, d) have limited indications, being useful principally in cases with more than 4 mm of keratinized gingiva (if a horizontal incision is placed in the context of attached gingiva) and in presence of lesions of limited size, since the mobilization of tissues to obtain access to the lesion could be difficult.

Managing the incision of the interdental papilla is critical. In Periodontology, over the years, techniques for the preservation of the interdental papilla have been described. In surgical endodontics, the preservation of the papilla was proposed by Velvart [18] and named the Papilla Base Incision technique (Figure 24.2). The preoperative papilla height is recorded by measuring the distance between the contact point and the most coronal aspect of the papilla. The papilla base flap, consisting of the papilla base incision and two releasing incisions, are used to expose the bone. The papilla base incision consists of a shallow first incision at the base of the papilla and a second incision directed to the crestal bone, creating a split thickness flap in the area of the papilla base. Further apically a full thickness flap is raised [18]. In general, preservation of the interdental papilla is always recommended in surgical endodontics since there is no need to involve it.

Figure 24.2 Illustrative drawing showing “Papilla preservation flap”. This type of flap is suitable for preserving the papilla and thus both the aesthetics and the functionality of the soft tissues.

The surgical flap must be elevated carefully, beginning from the point of conjunction between the vertical and the horizontal incision. After flap elevation, the root(s) and lesion can be located visually or identified using the preoperative radiographs to measure its position.

24.4.4 Bone Access

Once the flap has been elevated (full thickness) and the position of the root(s) and lesion identified, adequate access through the bone is required using the following guidelines:

• the bone access must allow adequate visualization of the lesion;
• the bone access must allow easy and complete removal of the lesion;
• the bone access must respect and preserve the critical anatomical structures that are close to the lesion (e.g. maxillary sinus, inferior alveolar nerve).

Progressive removal of bone tissue is useful in order to reduce the extent of the bone wound and thus minimize the invasiveness of the procedure. More recently, two techniques were proposed in order to minimize the extent of bone removal. The preparation of surgical guides, by 3-dimensional planning and computer-aided-design (CAD) could assist in limiting the size of the osteotomy [13]. More recently, computer-aided navigated surgery has been described in the field of EMS. Such techniques allow the surgeon to perform the osteotomy by visualising the position of the bur (or of the ultrasonic tip) on a monitor that displays a 3-dimensional reconstruction of the anatomy of the surgical site [15]. Even though computer-aided osteotomy (both with guides or navigation) are promising, they both need more scientific evidence to be validated.

Removal of bone, when required, could be completed using a round diamond long-shank bur in a straight handpiece. The bur should be used with abundant irrigation with sterile saline solution and at low speed, with a “brushing” movement, in order to avoid overheating the bone. More recently piezo-surgical devices have been used as an alternative for osteotomy. Such devices use ultrasonic vibrations and provide an alternative to the mechanical devices commonly used in Oral Surgery. The advantages of using a piezoelectric device include the possibility of more “conservative” bone removal, avoiding overheating the bone, and protecting the nerves and vessels (in general, all the soft tissues) when touched by the tip. However, piezoelectric devices (and tips) are usually slower than conventional burs [19].

Ideally, the soft tissue lesion should be removed in full, maintaining its integrity in order to facilitate histologic analysis of the entire specimen. The removal of the tissue must be performed using sharp curettes, avoiding the surrounding anatomical structures. When the lesion invades the maxillary sinus and is in contact with the maxillary sinus membrane, its removal may result in tearing of the membrane that should be managed later during the root-end preparation phase.

24.4.5 Root-end Management

Root-end management is one of the most critical phases of MS and EMS treatment since all clinical issues that are typical of orthograde treatment must be considered (e.g. canal preparation, drying phase, and 3-dimensional filling) but with limited visualization and less effective isolation.

The resection of the root should remove at least 3 mm of the apex (or apices), which removes most of the lateral canals that are present in the apical portion of the root. The decision on the extent of root resection must take into account the entire root length, since the resection of a large portion of the root could weaken the entire tooth, and modify the root-crown ratio [3].

The angle of the root-end resection should not exceed 10° (ideally from 0° to 10°) in order to limit the number and the diameter of exposed dentinal tubules. In the past, larger angles were preferred to overcome the limitations of visualizing the root-end and to help angulating the handpiece and bur when preparing the root-end cavity. More recently, the development of microsurgical techniques and instruments has improved visualization, thus reducing the need for greater angles of resection. The root-end can be resected and bevelled in one of two ways. Abrading the root-end using a carbide fissure bur (in a straight handpiece) under continuous irrigation with sterile saline solution is recommended in most cases because through a “brushing” movement, beginning from the root-end in a coronal direction, it is possible to control the amount of resected tissue [3].

The second technique is to predetermine the amount of root to be resected and to cut the root-end in a mesio-distal direction with one single movement in the determined position. Such a technique is recommended in all cases where anatomical structures are in close proximity to the root(s), such as the alveolar nerve or maxillary sinus. In such cases, resection maintains a safe distance between the bur and the anatomical structure. Some authors suggest removing the apex and the lesion together in one block [20