Visual aids such as loupes and the operating microscope provide the operator with excellent lighting and magnification. ¹⁸ The development of operating microscopes specifically for endodontics has been a recent advance that greatly enhances the operator’s view of the surgical site. However, there is a steep learning curve associated with the use of the operating microscope and proficiency demands regular and continuous use. The enhanced vision facilitates the location of a multitude of anatomical features not easily visible to the naked eye. These include isthmuses, fins, and additional or accessory canals. In addition, fractures, perforations and resorptive defects are more easily identified and managed.

The ability to achieve profound anaesthesia and tissue haemostasis in the surgical site is essential. Profound anaesthesia will minimize or eliminate patient discomfort during the procedure and for a significant period thereafter, whilst good haemostasis will improve vision at the surgical site, improve root-end cavity preparation and filling, minimize surgical time, and reduce surgical blood loss, postsurgical haemorrhage and postsurgical swelling. ⁵ An anaesthetic solution containing a vasoconstrictor is indicated to achieve these objectives. ¹⁹

The choice of the anaesthetic-vasoconstrictor combination is dependent on the health status of the patient and surgical needs. Lidocaine (lignocaine) with adrenaline (epinephrine) has long been recognized as an excellent anaesthetic agent for periradicular surgery because of its clinical success in producing profound and prolonged analgesia. ²⁰ Although several studies support the efficacy of 2% lidocaine with 1 : 200000 to 1 : 100000 concentrations of adrenaline for profound anaesthesia, ²¹ clinical evidence suggests that a 1 : 50000 concentration provides better haemostasis. ²² The prolonged postoperative pain relief is due to the inhibition of peripheral neuronal discharges, which in turn, helps reduce the subsequent development of central sensitization. ²³

Assessment of the patient’s systemic status is essential prior to the use of 2% lidocaine with adrenaline, especially 1 : 50000 adrenaline. This is important because lidocaine with adrenaline can elevate systemic plasma levels of the vasoconstrictor²⁴ although the haemodynamic response to this increase is still controversial. ²⁵ The potential rise in adrenaline concentration suggests that high-risk patients should be carefully monitored. Great care should be taken during injection to prevent intravascular placement of the solution. ¹⁹ When an anaesthetic with 1 : 50000 adrenaline is unavailable, 1 : 80000 is clinically acceptable. While 2% lidocaine with 1 : 100000 adrenaline is recommended for regional nerve blocks prior to endodontic surgery, this level of vasoconstrictor does not suffice for local haemostasis at the surgical site. Haemostasis must also be established at the surgical site²⁶ by additional injections supraperiosteally using 2% lidocaine with 1 : 50000 adrenaline. ²⁷

In healthy patients a dose of 2–4 ml is recommended. In the maxilla, achievement of both anaesthesia and haemostasis can be accomplished simultaneously. This requires multiple injections, depositing the solution throughout the entire submucosa superficial to the periosteum at the level of the root apices in the surgical site. The needle, with the bevel toward the bone, is advanced to the target site and, following aspiration, 0.5 ml of solution is deposited slowly (Fig. 10.2). The needle may be moved peripherally and similar, small amounts of solution deposited. Additional injections can be made to ensure that the entire surgical field has been covered. Slow, peripheral supraperiosteal infiltration into the submucosa promotes maximum diffusion (Fig. 10.3). In the mandible the anaesthetic–vasoconstrictor solution is injected slowly adjacent to the root apices, in addition to the block injection of the inferior alveolar nerve. Incisions that are made in alignment with the long axis of the supporting supraperiosteal vasculature coupled with careful elevation and reflection of the tissues, will minimize haemorrhage at the surgical site. ⁵

The amount of anaesthetic solution containing 1 : 50000 adrenaline that is necessary to achieve anaesthesia and haemostasis is dependent on the surgical site, but 2.0 to 3.0 ml will usually suffice. The rate of injection can also influence the degree of haemostasis and anaesthesia obtained, with a rate of 1 to 2 ml/min recommended. ²⁸ Injecting at higher rates will lead to localized pooling of solution, delaying and limiting diffusion into the adjacent tissues resulting in less than optimal anaesthesia and haemostasis. Predictable anaesthesia and haemostasis should be achieved prior to any incisions. Later attempts during surgery to improve anaesthesia and haemostasis are less successful. Following administration of the local anaesthetic, sufficient time must elapse prior to the initial incision (5–10 mins), to allow for proper vascular constriction throughout the surgical site. Other adjunctive agents are available to enhance the haemostasis during treatment. These will be discussed later in this chapter.

Good surgical access requires predetermined, meticulous tissue flap design followed by the incision and elevation of the soft tissue from the underlying bone. The design of the tissue flap is crucial not only to surgical entry and management of the root structure, but also to healing of the surgical wound. The design of soft tissue flaps has received wide and varied attention. For years, the semilunar flap (Partsch incision) in the apical loose alveolar mucosa was recommended but this has now been largely superseded. Various flap designs have been advocated based on a biological approach to tissue management and wound healing. The range of contemporary surgical flap designs⁵ is outlined in Table 10.3. There are strong biological reasons to consider the use of full mucoperiosteal tissue flaps whenever possible (Table 10.3). Figure 10.4, Figure 10.5, Figure 10.6, Figure 10.7, Figure 10.8 and Figure 10.9 detail diagrammatically each design, whilst the subsequent text gives a brief description of their application.

Prior to root-end resection and removal of any diseased soft tissue surrounding the root, bone may need to be removed to gain visual access to the surgical site. Removal of the bone is usually accomplished with a large round bur (ISO size 018 or 024), using a low- or high-speed handpiece. The bone is removed in a brush-stroke fashion with copious irrigation, creating a window over the root apex. Adherence to this technique will reduce the heat produced during the osteotomy procedure, thereby minimizing the potential for damage to the living bone tissue. In many cases, the osteotomy may need to be started from a coronal position, moving apically once the root structure has been identified. Care should be taken to avoid removing cementum from the root surface in order to prevent resorption at a later date. Entry as close to the apex, however, is recommended, with the angle of entry facilitating visibility and surgical access. Measuring the approximate length of the root on the bone, as estimated from the preoperative radiological assessment, facilitates location of the root apex (Fig. 10.17).

The apex may also be identified during osseous palpation after soft tissue reflection. Where the bone is thin, or the root apex is prominent, a straight bone curette can be used in a rotating motion to penetrate the cortical plate and identify the root structure (Fig. 10.18). In cases with large periradicular lesions, the loss of the cortical plate of bone may directly expose the root apex. Once exposed, the bur can be used to create a larger window to outline the root apex. In those cases where the bone is thick and location of the apex is difficult, the same type of initial osseous penetration can be made and a sterile radiopaque object placed in the hole. A radiograph will then provide additional information on the location of the root apex.

Root structure can be differentiated from surrounding bone by texture (smooth and hard), lack of bleeding upon probing, outline (presence of periodontal ligament), and colour (yellowish). The perimeter of the root and its periodontal ligament may also be identified by painting 1% methylene blue dye on the surface. ³¹

This procedure can often be performed prior to, or in conjunction with, root-end resection. The purpose is to remove the reactive tissue. ³² Contrary to previous belief, every remnant of this soft reactive tissue need not be removed to avoid failure, as the tissue elements in the periphery of these lesions usually contain fibroblasts, vascular buds, new collagen and bone matrix. In cases where the soft tissue mass is exposed upon flap reflection or initial bone removal, curettage can proceed prior to root-end resection. In other cases, resection is necessary to gain access to most of the tissue.

Curettage is accomplished with straight or angled surgical bone curettes and periodontal curettes (Fig. 10.19). Initially the bone curettes are used to peel the soft tissue from the lateral borders of the bony crypt. This is performed with the concave surface of the curette facing the bony wall, applying pressure only against the bone (Fig. 10.20). ³³ It is desirable to avoid penetration of the soft tissue as this may sever the vascular network, and increase local haemorrhage. Once the tissue is freed along the lateral margins, the bone curettes can be turned round and used in a scraping fashion along the deep walls of the crypt. This will detach the soft tissue from its lingual or palatal base. Once loosened, tissue forceps are used to grasp the tissue gently as it is teased from its position with a bone curette. The tissue sample is placed directly into a bottle of neutral buffered formalin or transport medium for biopsy. In cases requiring root-end resection prior to curettage, the root structure must be exposed sufficiently to minimize shredding of the soft tissues during resection. Despite profound anaesthesia at the surgical site as a whole, it is often found that the centre of the periradicular lesion remains sensitive. This is explained by the proliferation of neural endings stimulated by inflammatory mediators. ³⁴ Infiltration of local anaesthetic into the reactive tissue will invariably eliminate any residual sensation.

In the presence of large lesions, care must be exercised during curettage of the lateral surfaces of the bony crypt to avoid damage to adjacent roots and their pulpal vasculature. Presurgical radiographs should warn of this possibility, and tissue in these areas may need to be left in position. Caution is necessary to prevent damage to vital structures when operating close to the maxillary antrum, mental foramen, or mandibular canal. When soft tissue is adherent, either lingually to the root, or in the furcation region, periodontal curettes facilitate its removal. Periradicular curettage is normally performed in conjunction with resection of the root-end. ³⁵

It is evident from the literature that the vast majority of periradicular lesions are granulomas. However, a small percentage (0.7–5%) are reported to be different based on histological examination. ³⁶ These ‘other’ lesions include odontogenic cysts (odontogenic keratocyst, dentigerous cysts,), non-odontogenic cysts (globulomaxillary cyst, nasopalatine cyst), ossifying fibroma, Pindborg tumour, Langerhans cell disease, or osteoblastoma to mention just a few. More seriously, however, are lesions that might be neoplastic. Many reports exist in the literature documenting cases of misdiagnosis.^{37.38. and 39.} Considering the potential gravity of this situation, it is widely agreed that tissue excised during surgical endodontic procedures should be sent for histological examination. ⁴⁰

The term root-end resection refers specifically to the removal of the apical portion of the root. There are many indications for resection of the root-end during periradicular surgery, each designed to eliminate aetiological factors.

Historically, the technique of root-end resection involved the creation of a bevel on the root face, to improve surgical access and visibility.^{35.41.42. and 43.} The angle of resection was determined by the root inclination and curvature, number of roots, thickness of bone and position of the root in the bone. Current evidence indicates that reducing the angle of the bevel will reduce dentinal tubule exposure. ⁴⁴ Based on the number of dentinal tubules communicating between the root canal and the resected root face, the angle of the bevel should be kept to a minimum. ⁴⁴ A significant increase in leakage from the root canal system has been demonstrated as the bevel increased. ⁴⁵ Ultrasonic instruments have been developed that greatly facilitate preparation along the long axis of the root and, therefore eliminate the need for extensive bevelling of the root face.

The root-end can be resected in one of two ways. First, after the root-end has been exposed, the bur (narrow straight fissure) is positioned at the desired angle and the root is shaved away, beginning from the apex, cutting coronally (Fig. 10.21). The bur is moved from mesial to distal, shaving the root to a smooth and flat finish until the entire canal system and root outline is exposed. As mentioned earlier, the root outline can be more easily visualized by staining the periodontal ligament with 1% methylene blue dye. ⁴¹ This approach allows for continual observation of the root-end during cutting. The second technique of resection is to predetermine the amount of root-end to be resected. The bur and handpiece are positioned, and the apex is resected by cutting through the root from mesial to distal (Fig. 10.21). Once the apex is removed, the root face is gently shaved with the bur to smooth the surface and ensure complete resection and visibility of the root face. This technique works well when an apical biopsy is desired, or to gain access to significant amounts of soft tissue located lingual to the root. It is also the technique of choice in cases where the root-end is located in close proximity to structures such as the mental foramen or the inferior alveolar canal. The disadvantage however, is that this approach may remove more root structure than necessary.

The appearance of the root face following root-end resection will vary depending on the type of bur used, the external root anatomy, the anatomy of the canal system exposed at the particular angle of resection, and the nature and density of the root canal filling material. Various types of burs have been recommended for root-end resection; ⁵ each will leave a characteristic imprint on the root face, from rough-grooved and gouged to smooth. ⁴⁶ To date, no study has determined the advantages of one type of bur over another, although for years clinical practice has favoured a smooth flat root surface. ⁴⁷

The level to which the root-end should be resected will be dictated by the following factors: ⁵

Regardless of the rationale for the extent of root-end removal, there is no reason to resect the root to the base of a large periradicular lesion as was previously advised. Likewise, resection to the point where little (<1 mm) or no crestal bone remains covering the buccal aspect of the root may very well doom the tooth to failure (Fig. 10.22). On the other hand, omitting to remove sufficient root structure to be able to inspect the resected root face and place a root-end filling may also contribute to failure. Root canals or anastomoses may be missed, or may be improperly managed in confined spaces.

The complete root face must be identified and examined after resection. This is inspected, preferably under high magnification and good illumination, with a fine, sharp probe guided around the periphery of the root and the root canal. The external root anatomy will determine the ultimate shape of the cut root-end, such as oval, round, dumb-bell shaped, kidney-bean shaped, or tear-drop shaped (Fig. 10.23). The outline of the resected root-end will vary depending on the tooth, angle of any bevel and position of the cut on the root. However, the entire surface must be visible. If visibility is impaired, or the root has an unusual cross-section, 1% methylene blue dye can be placed on the root face for 5 to 10 seconds using a sterile sponge applicator and rinsed off with a stream of sterile water or saline. Cotton pellets should not be used as remnants of cotton fibres left in the surgical site have been shown to induce a foreign-body reaction in healing tissues. ⁵ The dye will stain the periodontal ligament dark blue, highlighting the root outline. ⁴¹ The shape of the exposed canal system will vary depending on the angle of the bevel and the canal anatomy at that level. Canal systems will generally assume a more elongated and accentuated shape with increasing angles of bevel (Fig. 10.24).

Also visible on most resected root-ends is the presence of root canal filling material and the interface between the filling material and the root dentine. Variations in quality of the filling will be seen in both the type of filling material and the nature of the filling technique (Fig. 10.25). Furthermore, the different burs used for resection will create discrepancies in the surface of the filling material and its adaptation to the canal walls. For example, coarse diamond burs will tend to rip and tear at the gutta-percha root canal filling, spreading the gutta-percha over the edge of the canal aperture and onto the resected root face (Fig. 10.26). Surface finishing with an ultra-fine diamond is recommended (Fig. 10.27) (Ultrafine no. 862-012 diamond bur, Brasseler, Savannah, GA, USA).

The presence of additional canals, anastomoses, fracture lines, and the quality of the apical adaptation of the root canal filling must be checked on the resected root surface (Fig. 10.28). If methylene blue dye has been used, it will also stain the periphery of the canal system and highlight fracture lines. A fibre-optic light can be aimed at, or behind, the root-end to enhance visibility. ⁹ Sometimes, it may be necessary to remove additional root structure to identify the canal system or, in the case of a fracture line, to observe its direction and extent.

A major area of concern following root-end resection and dentinal tubule exposure is the possibility that these tubules may serve as a direct source of contamination from the uncleaned root canal system into the periradicular tissues. Root-ends resected from 45° to 60° have as many as 28000 tubules/mm² immediately adjacent to the canal. ⁴⁴ At the dentino-cemental junction, areas that may communicate with the root canal even in the presence of a root-end filling 13000 tubules/mm² are found. Likewise, due to angular changes in the tubules at the apex, there could be patent communication with the main canal if the depth of the root-end preparation in the buccal aspect of the cavity is insufficient. ^48,49 Root-end resections in older teeth have shown less leakage than that seen in teeth from younger patients; ⁵⁰ this corroborates with the findings of sclerosis and reduced patency in apical dentinal tubules. ⁵¹

Another concern following root-end resection is the formation of a contaminated smear layer over the resected root-end (Fig. 10.29). This may serve as a />