(a) Radiograph of an upper lateral incisor with a long parallel post showing an incomplete root canal filling and a periapical radiolucency. Endodontic treatment options can either be conventional retreatment after removal of crown and post or surgical retreatment. Considering the relative narrow root in relation to the size of the post and possible risk for inducing root fractures, surgical retreatment is considered as the first choice of treatment. (b) The retrograde instrumentation of the canal was performed with hand files held in a haemostat. To maintain the curvature of the canal flexible files can be a better alternative than stiff ultrasonic tips when longer instrumentations are needed. (c) Postoperative radiograph with a retrograde filling to the level of the post
On the other hand, irrespective of the quality of the former treatment, surgical retreatment is considered to be the first choice where orthograde retreatment has failed to control the infection or cannot be undertaken due to blocked canals caused by dystrophic calcifications and iatrogenic errors such as ledges, broken instruments and presence of posts (Figs. 7.2 and 7.3).
(a) A lower left first molar with an incomplete root filling and periapical radiolucencies on booth roots. Surgical retreatment was performed as an alternative to conventional retreatment. A partly or completely obliterated mesial root can be suspected from the radiograph that can be challenging to treat. The patient was eager to keep the crown and post in order to reduce the costs. (b) A postoperative radiograph with a limited retrograde preparation and filling in the mesial root. (c) Five years postoperatively, the patient developed pain from the area. The radiograph showed a nice bone healing on the first molar, but the second molar had developed a periradicular bone lesion found to originate from a root fracture
(a) Radiograph of the upper left first molar with a fractured instrument in the mesiobuccal root diagnosed with symptomatic apical periodontitis. Due to the difficulties in removing instrument without extensive risks for complications when located in the apical third of the root with a root curvature, surgical retreatment was performed. (b) Immediately postoperatively. (c) A 1-year follow-up
7.2.2 Biological Considerations
From microbial perspective, surgical retreatment is indicated when suspecting a persistent infection withstanding the effect of an impeccable root canal treatment. Even though persistent infections are mainly localised in the root canal system, microorganisms can establish an extraradicular infection formed as a biofilm on the root surface adjacent to the root apex and even colonizing the periapical tissue [12, 13]. However, to what extent an extraradicular infection can persist without the intraradicular infection as a reservoir is not well understood  and a surgical retreatment should therefore focus on treatment of all possible infection sites.
Most periapical lesions can be classified as dental granulomas, root cysts and abscesses [15, 16]. Periapical lesions cannot be differentiated based only on the radiographic observations . However, a correlation has been shown between the radiographic lesion size and the probability for cystic lesions [18, 19]. Based on histological criteria, two different categories of cysts have been defined [20, 21]: True cyst which have complete enclosed lumina and therefore no direct connection to the root canal and pocket cysts that have open connection to the root canal. True cyst, different from pocket cysts, may therefore be self-perpetuating and fail to heal if not treated surgically.
Foreign body material can accidentally be displaced to the periapical tissue during endodontic treatment. The presence of a foreign body in the periapical tissues may cause endodontic failure by triggering an inflammatory response and a subsequent foreign body reaction, which can be treated successfully by surgical retreatment.
A local deep pocket is generally an aggravating factor for the prognosis (Figs. 7.4 and 7.5). Tentative diagnoses are periodontal fistulation, root fracture or an endo-perio lesion either caused by primary or secondary periodontal disease. The benefits with a surgical approach are the possibilities to explore the root and evaluate for eventual fractures and supplement if necessary with a periodontal treatment.
(a) First lower right molar with a persistent pathology after orthograde retreatment. (b) Adjacent to the fistula a local pocket was probed to the apex. No root fracture could be found after exploration. (c) The radiograph shows a periradicular radiolucency on the mesial root. The mesial root was surgically retreated with a questionable prognosis then it is difficult to know if a secondary periodontal lesion had developed
(a) Upper right second premolar with a deep pocket located buccal. (b) An exploration was made in order to inspect the root surface. (c) A vertical fracture line was found after removing the soft tissue and staining with methylene blue
With an extensive marginal attachment loss in periodontally compromised teeth, the possibilities to perform a surgical treatment may be limited. Osteotomy for apical resection reduces longitudinal width of the buccal bone that increases the risk of endo-perio communication. Moreover, with the surgical approach, the apical part of the root is resected and the crown-to-root ratio of the tooth may be unfavourable for the prosthodontic prognosis. The evaluation of tooth mobility preoperatively and the bite forces can be crucial to the possibilities of treatment.
7.2.3 Anatomical Considerations
A preoperative judgement of the accessibility of the site of infection is central for the successful outcome of the procedure. Careful evaluation of two or more periapical radiographs exposed in different angulations is mandatory (Fig. 7.6), and for certain cases, computed tomography is a good complement for planning and performing the treatment (Fig. 7.7).
An upper molar with a symptomatic apical periodontitis. (a) The radiographs showing a periapical radiolucency and fractured instrument in the apical third of the mesiobuccal root. (b) With a mesial eccentric radiographs, the root-filled canal in the mesiobuccal root moves from the x-rays, not centralised in the canal, indicating a second untreated canal
Orthopantomogram showing a patient with need of extensive fixed prosthodontic treatment. Evaluation of suitability of the upper jaw for installing implants showed poor bone conditions. The radiographic examinations showing periapical radiolucencies on several teeth (13, 22 and 26). Thirteen and twenty-six are restored with well-functioning posts and not planned for removal. Surgical retreatment was planned. A CBCT in axial, frontal and sagittal view and periapical radiograph of the first left maxillary molar showing periapical radiolucencies around all roots. In between the roots there is a sinus recess. Only a minor swelling can be seen in the sinus mucosa. The postoperative radiograph showing the retrograde fillings performed by a buccal entrance
Most roots are accessible for surgical treatment. In the lower jaw, proximity to the mandibular nerve and/or a thick cortical bone buccal to the tooth may limit the accessibility. Extended preoperative radiographic examination with cone beam computed tomography CBCT is recommended in such cases. The palatal root can either be treated by a buccal or palatal entrance. The relation to sinus and indications for treating the buccal roots is crucial for the decision (Fig. 7.8). A palatal entrance is technical demanding not at least depending on the difficulty raising the flap and get a good insight (Fig. 7.9). In cases were the accessibility to the palatal root is limited surgically especially for the second maxillary molars, a combined intervention may be considered with a conventional orthograde treatment of the palate root.
Surgical treatment of tooth 26 was performed by a buccal entrance . (a) After removing the soft tissue and performing the root resection of the buccal roots a perforated sinus membrane was found. (b) As the sinus membrane was perforated, access to the palatal root could be achieved from sinus. The arrow showing the apex of the palatal root covered by the sinus membrane and bone. (c)The palatal root is seen after drilling through the covering tissue. (d) The palatal root after root resection. (e) Inspecting the mesiobuccal root by a micro mirror. The root filling in the canal showing a void. Parts of the isthmus in between the canals are seen. (f) Gauze is packed into the sinus in order not to introduce infected material or inadvertently drop instruments into the sinus. The canals and the isthmus are prepared by a contra-angled ultrasound tip
(a) First left maxillary molar with an apical radiolucency related to the palatal root according to the intraoral radiograph. Due to long post and a well-functioning crown, a surgical retreatment was planned. (b) Showing the palatal flap and the fenestration of the palatal bone plate
The location of the lesion, root anatomy, relationships of roots and relation to neighbouring anatomical structures and findings that indicate untreated channels are of special interest for treatment planning. Once again, CBCT is a powerful tool that can assist when a more exact three-dimensional imaging of the tooth and the periapical tissue is necessary  (Fig. 7.7).
For supporting the clinician in the preoperative planning, a guide with different categories of complexity of lesions has been presented  where the more severe categories are demanding and may need certain surgical skills, techniques and equipment.
The location of the root in the alveolar process and possible involvement of neurovascular structures may hamper the opportunities for access. Nerve injuries and altered sensation is however rarely reported after surgical retreatment. It can occur as an effect of nerve traumatised during surgery or following local anaesthetic administration, or indirectly caused by a postoperative inflammation when performing treatment in the vicinity of major nerves. The risk to injure the inferior alveolar nerve is related to treatment of second molar and premolars but also to some extent first molars .
Surgical treatment on teeth with apex or a periapical lesion in close apposition to the maxillary sinus should be carried out with caution (Fig. 7.8). Removal of infected tissue should be performed carefully, in order to avoid perforation of the sinus membrane.
Sometimes the membrane is disrupted due to the inflammatory reaction. In such cases, special attention has to be made to not introduce infected material or inadvertently drop instruments into the sinus. This can be prevented by packing the sinus with gauze. A final thorough rinsing with saline is important to ensure removal of infected material in the sinus.
More extensive lesions that have destructed the cortical bone plates with a through-and-through lesion may end up with incomplete bone healing with fibrous tissue ingrowth (scar tissue)  (Fig. 7.10). A situation that may be only indication for where a guided tissue regeneration technique may be indicated .
A sequence of healing after surgical retreatment of tooth 12. (a) Immediately postoperatively (b) A 1-year follow-up with a reduction of the defect in the bone. (c) A 4-year follow-up showing a feature of incomplete scar tissue healing with continuous periodontal ligament and a separate lesion
With larger lesions, other tissue structures distant from the tooth may be involved and can complicate the treatment and certain precautions have to be made. More teeth may be necrotic and involved in the process and therefore the vitality of neighbouring teeth has to be evaluated before surgery. Due to the surgery and soft tissue curettage teeth not involved in the process may be devitalised due to the treatment.
Radiographic evaluation of the size and the location of the bone lesion may give an indication to where in the root the infection is localised. An important question is whether lateral canals or untreated canals may be involved (Figs. 7.6 and 7.11), and if these are accessible for treatment during surgery. Also, any external inflammatory root resorption that may have occurred should also be localised and held as a potential exit of intra-canal infection when treating the root.
(a) An upper right canine with a juxtaradicular radiolucency. (b) A lateral canal (arrow) was located after exploration and staining with methylene blue
Even if the impression from the intraoral radiographs is that the tooth has separate root canals, anatomical studies have shown a great variety in morphology and complexity of the canal system . Canals may branch, divide and rejoin, end in apical ramifications and have accessory canals and roots with more than one canal having isthmuses (Fig. 7.8). All these anatomical sites may function as a bacterial reservoir and are crucial to properly treat.
Where there is poor supporting bone tissue surgical retreatment may be contraindicated due to the doubtful prognosis. Teeth with endodontic-periodontal lesions may exist separately and later unite together in a combined lesion, or it may be primarily endodontic or periodontal with a secondary involvement of the other (Fig. 7.4). Due to the risk for down growth of a long junctional epithelium and subsequent hindrance of a favourable healing with bone and reattachment, the outcome is compromised [28, 29].
In cases with long posts especially in metal, leaving a limited canal space may influence the possibilities to perform enough deep retrograde filling for a proper seal and alternative techniques may be considered. This can also be the situation in case of post perforation with limited possibilities to create a cavity preparation (Fig. 7.12).
Upper right canine with a long post and juxtaradicular and periapical radiolucency . An exploration showing a buccal post perforation. The perforation was covered by a composite with a dentine bonding agent after drilling a minor cavity
7.2.4 Medical Considerations
Considerations of medical risks are essential for all dental treatments but special precautions should be taken when planning for surgery. For every treatment, a risk assessment has to be performed based on a careful medical history and in some cases after consultation with physician. For medically compromised patients, orthograde procedures usually expose them to less medical risks than surgical treatment. Therefore, a non-surgical approach to endodontic retreatment may be more suitable. For certain medical conditions, the surgical treatment should be postponed until the patient has recovered. However, there are no absolute medical contraindications to endodontic surgery.
An overall estimate of the medical risk can be made due to the physical status classification system adopted by the American Society of Anaesthesiologists (ASA) in 1962 with a modification in five categories to the dental treatment situation .
There are several medical conditions and medications that cause a depressed immune system, where surgical intervention is contraindicated until white blood cells count and antibody levels have normalised.
Patient with increased risk for bleeding needs special attention. Medication with antiplatelet and anticoagulant agents increases the bleeding time intra- and postoperatively. Surgical treatment is possible in most cases but needs certain treatment protocols. Surgical treatment of patients with haemophilia or impaired liver function should only be after consultation and in agreement with the patient’s physician.