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N.P. CHANDLER and S. KOSHY
Department of Oral Rehabilitation, School of Dentistry, University of Otago, New Zealand
Keywords: Root canal treatment, apicectomy, endodontic surgery
Enormous progress has been made in the last quarter of a century in understanding the nature of root canal infection and periapical disease. New techniques and materials may be expected to increase the already high success of conventional root canal treatment. Surgical intervention is required for cases where retreatment has failed or is not an option, and the tooth is to be retained rather than extracted. This article reviews the operation of apicectomy and how this minor oral surgical procedure has evolved. Recent modifications to techniques and materials are likely to improve its success, allowing conservation of previously unsaveable teeth
J.R.Coll.Surg.Edinb., 47 October 2002, 660-667
The American Association of Endodontists defines apicectomy as the excision of the apical portion of the tooth root and attached soft tissues during periradicular surgery.1 Endodontic therapy eliminates root canal flora by chemomechanical debridement followed by obturation of the canal to achieve a seal.2 Clinical, radiographic and histological observations are the criteria for evaluating success. The percentage of success reported has been consistently high.3-6
Failures may arise due to inadequate control of infection, poor design of the access cavity, inadequate instrumentation and obturation, missed canals and coronal leakage.7 Factors for persistence of periapical radiolucencies after conventional root canal treatment in well treated cases may be intraradicular infection, extraradicular infection, foreign body reactions and true cysts.8-13 Failures may be retreated, receive endodontic surgery or the problem tooth extracted. Consensus has been reached by researchers regarding the importance of debridement, obturation and coronal seal on the outcome of treatment.5,6,14,15
The first cases of endodontic surgery were those performed by Abulcasis in the 11th century.16 A root end resection procedure to manage a tooth with a necrotic pulp and an alveolar abscess was documented in 1871 and root end resection with retrograde (root end) cavity preparation and filling with amalgam in the 1890’s.17,18 Some researchers, however, claim Claude Martin as the inventor of root end resection in 1881.19 Endodontic surgery was often considered as an alternative to root canal treatment and indications for surgery were proposed first in the 1930’s.20 The rationale for performing apicectomy has changed over the past 120 years. The current view is that retreatment by conventional methods is the preferred alternative to apicectomy.21,22
In the 1960’s, surgery was indicated in a non-vital tooth if instrumentation had not reached within 2.5 mm of the root apex.23 The level of unfilled or poorly filled canal determined the level of resection, and at that time the cut was bevelled towards the labial surface to improve visualisation and ease of placement of a root end filling (Figure 1).24 The contraindications were uncontrolled periodontal disease and some systemic conditions. The preparation and filling of the root canal was performed either before or at the time of surgery. There was little evidence to show any increase in the rate of success by preparing and delaying the root canal filling until two consecutive negative cultures were obtained following antibacterial treatment. At that time appropriate anaerobic culturing techniques were not available, and calcium hydroxide was not in major use as a medicament. Also, in the 1960’s it was believed that the main cause of endodontic failure was a poor apical seal.3
Studies have reported the success of endodontic therapy and it varies from 40% to 96%.3-6,15,25 Many studies, however, lacked proper controls and have conflicting definitions of success and failure.
In a study of 356 patients evaluated 8 to 10 years after treatment the success reported was directly dependent on the pre-operative status of the pulp and periapical tissues.5 In this particular study, Strindberg’s radiographic criteria were used to judge the success rate of endodontic therapy together with clinical records.4 The criteria were (a) the contours, width and structure of the periodontal ligament space were normal or (b) the periodontal contours were widened mainly around an excess of filling material. Other standards for success were the level of the root filling, which was considered adequate when there was no lumen apical to the filling and no voids in the apical part. Radiographs were interpreted twice at different intervals by two independent observers, as suggested by Molven et al (1996), with variable illumination and magnification.5,26 The success rate was 96% for teeth with vital/non-vital pulps with no initial periapical radiolucency. Of the group with prior pulp necrosis and periapical radiolucency, 86% had healed. Roots well-filled to the apex or within 2 mm of the apex had a success rate of 94%.5 For a favourable prognosis, instrumentation and filling to an optimal level is desirable.
Radiographic evaluation is important, with increased size or development of a lesion considered to be a failure.6,27 A radiographic follow-up to 4 years is satisfactory for determining success.3,5,6 Biological and technical failures continue to occur as there are parts of root canals where debridement and obturation are not adequate. The reasons for persistence of a radiolucency in what seem well treated cases are not yet fully understood.7
New developments in root canal treatment in the last 10 years include an increased use of microscopes, preparations using ultrasound, canal preparation with rotary nickel titanium instruments and new obturation techniques and materials. These innovations might improve success of treatment, and hence reduce the need for surgery.
Bacteria are the main cause of periradicular disease.28,29 Endodontic retreatment is indicated where there are technical deficiencies, procedural errors, pain, swelling or a sinus tract, persistent symptoms and when a new coronal restoration is planned.30 The success of retreatment is higher if non-surgical techniques can be performed, and the success of surgery is higher when it is supplemented by non-surgical retreatment.2,31 For non-surgical endodontic retreatment the reported success rates vary from 60% to 98%.2,5,32 In roots with periapicallesions which were previously filled and revised, the success rate was 62%, while 98% of the roots which underwent root filling due to technical deficiencies healed.5 A recent study reports that the predominant microbial flora in failed cases was Gram positive (mainly Enterococcus faecalis) and the overall success rate in these circumstances was 74%.25 Some bacteria such as Actinomyces and Arachnia propionica can prevent normal healing due to their capacity to survive in periapical tissues where they are inaccessible to conventional endodontic therapy.33
In a study of 2,308 teeth with periapical lesions Bhaskar (1966) found that 42% of the lesions were cystic.34 Garber (1964) reviewed 1000 patients who had root canal treatment and reported that it was impossible to distinguish a cyst and a periapical granuloma from radiographs when the lesion was small.35 Winstock (1980) in a study of 6091 cases that were followed up for a sufficient period reported that 8.4% were diagnosed as cysts and 83.3% as periapical granulomas.36 This study failed to report the follow-up period and the histological sampling methods employed. The incidence of radicular cysts amongst periapical lesions is around 15%, but variations ranging from 6% to 55% have been reported.12,37-40 The discrepancy is due to sectioning of the sample and histological interpretation.41 The highest incidence of cysts is associated with maxillary lateral incisors.37 Simon (1980) classified radicular cysts into two categories, those containing cavities fully enclosed with epithelial lining and those containing epithelial linings that are open to the root canals (bay cysts).12
These were later renamed apical true cysts and apical pocket cysts by Nair et al (1996) who reported the incidence of true cysts as 9% and pocket cysts as 6%.38 Many cases in which an apicectomy has been performed based on the radiographic diagnosis of the presence of ‘cysts’ might have been resolved by conventional treatment. A high percentage of periapical cysts resolved following non-surgical treatment and reduced the need for unnecessary surgery.42 The diagnosis of a ‘cyst’ without performing a biopsy is questionable. True cysts, however, are less likely to be resolved by conventional root canal therapy.13 Success rates of 85-90% have been reported after conventional root canal treatment with healing of periapical cysts.43,44 Radiometric analysis of digitised radiographic images may help to differentiate between radiographic lesions that are visually indistinguishable.45 Differentiation of a radicular cyst and granuloma using computerised tomography has also been reported.46
Studies of 2,039 apicectomy cases from the 1930’s to the 1960’s reported a success rate ranging from 34% to 99%, with a mean success rate of 82.5%.47-51 The length of follow-up varied from 9 months to 60 months in the studies and criteria for success were not uniform. A study of 797 apicectomies reported a success rate of 64% with the best results found when root filling and apicectomy were carried out at the same visit and when the periapical lesion was less than 5 mm in diameter.52 This is in agreement with an earlier study.53
Figure 1: Illustration to show bevelled (left) and non-bevelled (right) apical root resections.
Figure 2a: Very large periapical radiolucency related to non-vital upper left lateral incisor with root resorption. Figure 2b: Operator unable to dry canal. Radiograph 16 months following root filling, apicectomy and root end filling with MTA at a single visit. Excellent bony healing, crown to be permanently restored. Pathology report: periapical granuloma.
The prognosis of symptomatic teeth with calcific metamorphosis treated by non-surgical root canal treatment has been investigated and a success rate of 80% was reported over a 4 year follow-up period.54 No studies have compared the relative success of treatment of pulp canal obliteration using surgical procedures.55
In one thousand cases, with a radiographic follow-up from 1 to 15 years after apicectomy, it was found that most of the healing changes took place in the first year and only a few cases shifted into other healing groups after 4 years of observation.31 It has been indicated that with an observation period of 4 years the complete healing and unsuccessful groups increased while the incomplete and uncertain groups diminished.56 These findings are in agreement with previous studies.51,53
The technical procedures of apicectomy have been described and the routine placement of a root end restoration has been questioned.57,58 Root end filling was considered desirable when an unsuccessful root canal treatment was corrected by an apicectomy rather than by retreatment through the coronal access.59 The root end filling is to provide a seal or to improve the seal of an existing root canal filling. Retrofilled roots showed a failure rate of 27%, compared with 3.6% in cases filled at the surgical appointment by the orthograde method.60 Root end fillings should be placed routinely at apicectomy unless orthograde endodontic treatment has been performed in conjunction with apicectomy.61
In a study of 35 teeth where the root canals contained a post, a technique of retrograde root canal treatment was investigated. The canals were shaped in a retrograde manner with Hedström files and obturated with gutta percha softened in chloroform. The success rate was 71% and the follow-up period was more than 4 years.62
Studies evaluating apicectomy of the posterior teeth are limited. In a retrospective study of 32 apicectomies performed for posterior teeth the indications for apicectomy were cysts, chronic apical infection, failed endodontics and root resorption. The success rate was 62% when judged by radiographic and clinical criteria.63 Ericson et al (1974) reported a study of 314 maxillary canines, premolars and molars which had undergone apicectomies and the procedure proved successful for 54%, uncertain for 25% and unsuccessful for 21%.64 The sample included only 10 molars and the maxillary first premolars had a success rate of only 44%, which was the lowest. Apicectomy procedures on 160 molar teeth analysed in three studies indicated a mean success rate of over 70%.65-67 Friedman et al (1991) on the other hand reported a success rate of 44%, uncertain in 23% and unsuccessful in 33% of the 136 roots where the apicectomy procedure, was performed. In that study, the radiographic results were recorded according to criteria set out by Rud et al (1972) but with one difference.56 Even a small remaining radiolucency in the periodontal ligament space was recorded as incomplete healing, but the clinical criteria were less stringent than other studies.52,64,69 Clinical failure was determined by tenderness to percussion irrespective of radiographic appearance. The success rate was lower than the molar apicectomy procedures in previous studies.65-67
Figure 3a: Root filled upper left central incisor with root canal post in place. Failed apicectomy and root end filling of amalgam. Figure 3b: One year following second apicectomy with MTA root end filling. Good healing, tooth now restored with crown. Pathology report: periapical granuloma.
In a recent study with a rigorous surgical protocol, apicectomy was performed on 102 teeth of which 62% were premolars and molars that had been retreated non-surgically previously.22,70 A success rate of 91% was achieved using radiographic evaluation criteria and clinical evaluation of signs and symptoms of disease or loss of function.27,71 The high success rate could be due to well-defined case selection including eliminating cases with severe periodontal diseases, vertical root fracture, perforations of the furcation, resorptive processes involving more than the apical third and inadequate final restoration before surgery.
The radiographic assessment of healing patterns after apicectomy differs from that of conventional endodontic treatment by having an incomplete healing (scar tissue) group. In a follow-up study of 24 cases treated by periapical surgery reported 2-6 years postoperatively, one failed, one healed and 22 remained in the same group. It was concluded that incomplete healing (scar tissue) at the one year follow-up could be regarded as a success. 27
The current indications for apicectomy are:72
• Inability to perform conservative endodontic treatment due to anatomical, pathological and iatrogenic defects in the root canal
• Blockage of the root canal due to calcific metamorphosis or radicular restoration
• Medical reasons and time factors
• Persistent infections after conventional endodontic treatment- intraradicular/ extraradicular
• Need for biopsy
• Need to evaluate the resected root face for any additional canals or fracture.
Adjuncts to the apicectomy procedure have been reported and include the use of a membrane to enhance and encourage bone healing following apicectomy, the aim being to permit new bone formation rather than fibrous connective tissue.73
Persson (1973) reported a retrospective study of 129 cases of repeat apicectomy.74 The success rate was about 35% and follow-up of more than one year was recommended. In the study, about 25% of the cases were reoperated within one year, mainly because of clinical signs and symptoms rather than radiographic appearance. Sealing of the canal apically is necessary for success.75 (Figure 3). Peterson and Gutmann (2001) compared 8 studies on the basis of a weighted average of healing outcomes and reported a failure rate of 38%.76 The success rate of 64% for the initial apicectomy was significantly greater than the 36% for the repeat procedure.
Evaluation of the quality of root fillings varies among observers. A decision tree with possible alternatives for the management of a root filled tooth with periapical pathology can be constructed. Reit and Grˆndahl (1984) reported a study of 35 observers who were experienced clinicians very interested in endodontics.77 They were given 33 asymptomatic cases of teeth with varying sizes of periapical radiolucency. They viewed standardised radiographs under magnification and were asked to record their choice of action. There was considerable inter- and intra- observer variation in decision making.
In a retrospective study of 392 cases to evaluate the clinical factors involved in the decision to perform an apicectomy the reasons were classified as biological, technical and a combination of both.72 The biological factors are persistent symptoms, canal not dry and dimensional change in radiographic appearance. The technical factors were post crown restored teeth, fractured instruments, open apices, perforated root canals, presence of old root canal fillings which could not be removed and sclerosed canals. The technical factors amounted to only 3.3% while biological factors were 35.2% of the sample. The commonest biological factors were persistent symptoms after conventional root treatment (54.1%) and the presence of a periradicular lesion (44.1%). Of the technical factors, 60% were post crowns and 31% were crowned teeth without posts.72 In a retrospective study of 1300 patients who had undergone endodontic retreatment, 45.8% of the cases were retreated conventionally, 25.5% had an apicectomy performed and 28% had an apicectomy with a root end filling.21 Nonsurgical retreatment had a success rate of 72.7%, while of those who had an apicectomy 51.4% were successful, compared with 60% for apicectomy with root end filling.
In a study where surgical and non-surgical procedures were randomly allocated to 95 ‘failed’ cases and outcome was followed up for 4 years, it was concluded that there was no difference in the outcome. However, during the 12 month recall a higher healing rate was observed for surgical cases, but this gradually declined.78 During apical surgery the mucoperiosteal flap is affected by incisional wounding while dissectional wounding affects the mucoperiosteal and osseous tissues. Excisional wounding involves the periradicular and radicular tissues. Healing of the dissectional wound is rapid, although it is slower than the incisional wound. Fibrous connective tissue is formed 14 days after surgery.79 Surgical retreatment seems to result in more rapid periapical bone infill and caused more discomfort . It also tended to involve more indirect cost than non-surgical treatment.80
The construction of Receiver-Operating-Characteristic (ROC) curves offers a means of assessing a methods ability to detect the presence or absence of disease among several individuals. In endodontic radiology, ROC curves have been applied diagnosing whether a root is diseased. The detectability depends on the size and location of the lesion in the bone and on the cognitive ability of the observer.81,82 The radiographic diagnosis of periapical disease may be regarded as a signal-detection task.83 The observer along a continuum of observations sets criteria of a cut off point, and above that the presence of a signal is reported. The values are extrapolated to establish a ROC curve. A weakness of this scoring system is it is difficult to apply to clinical practice. The periapical index (PAI) scoring system is a visual reference scale for assigning a health status to the root and this can be analysed by ROCs. 84
During the 1980’s more than 1 million root canal treatments per annum were provided in the UK under the National Health Service.85 Some 50,000 were apicectomy procedures. In England and Wales, the number of apicectomy procedures is decreasing, the percentage having dropped from 5% in 1980 to 1.3% of the root canal treatments provided in 2001.86 This could be due to increasing levels of skill among general dental practitioners (GDPs), the increased availability of specialists in NHS hospitals or the gradual establishment of endodontic specialists in the UK. In a survey of endodontics in New Zealand (NZ) in 2000, 90% of practitioners felt that surgical cases and retreatment were major factors in their decision to refer.87 Only 37% of the NZ GDP’s did apicectomies in 2000, compared with 68% in 1980.87,88 A survey reported that 57.3% of GDPs in Scotland performed apicectomies.89 In the UK, 80% of referrals to hospitals from GDP’s requesting periradicular surgery failed to meet prescribed guidelines, mainly due to an unsatisfactory root canal filling.90,91 This indicates a lack of knowledge of the nature of treatment failure and the merits of retreatment. In many institutions, endodontists and oral surgeons carry out apicectomies. The success rate for apical surgery performed in a hospital endodontic unit was higher than that in the oral surgery unit of the same hospital.92
Figure 4: Schematic illustration showing (a) resected root with root end filling; (b) root canal filling; (c) coronal barrier which protects root filling in case of leakage; (d) coronal restoration.
Case selection and planning with good visual and manipulative access is a prerequisite for the success apicectomy. Selecting the most appropriate flap design and knowing the advantages and disadvantages of the full and limited mucoperiosteal flap designs, coupled with proper reflection and retraction, contributes to success. The haemostatic requirement is different to that for general dentistry.22 The use of adrenaline at a 1: 50,000 concentration in local analgesics is recommended and other procedures, such as the use of ferric sulphate in the bony wound, have been advocated.
Enhanced vision may improve the quality of the procedure and surgical microscopes are recommended.93 Pecora and Andreana (1993) in a study of 50 apicectomies, reported that the surgical microscope enhanced or facilitated each phase of surgery and trauma to both soft and hard tissues were minimised.93 Leakage around root end fillings contributes to the failure of treatment. The angle of the bevel on the root face should be minimal, reducing the number of exposed dentinal tubule orifices, and the recommendation made that root end fillings should extend beyond the level of the most coronal part of the bevel 94 (Figure 4). By increasing the depth of the root end filling and having a zero degree angulation to the long axis, apical leakage can be minimised (Figures 1,4).95 Cavity preparations are now carried out with ultrasonic instruments along the long axis of the canal rather than with a bur.96
A retrospective clinical study of amalgam, Super EBA and IRM concluded that success rates for IRM and Super EBA were significantly higher than amalgam as a root end filling material.97 Super EBA, IRM and Mineral Trioxide Aggregate (MTA) are the materials currently in use as root end fillings. Results with MTA are very promising.98 Root ends filled with MTA may have a complete layer of cementum over the root end following healing and no evidence of inflammation.99 These major changes in techniques and materials in the last decade may have a marked influence on success.
A disproportionate amount of apical surgery was based on the ‘diagnosis’ of cysts. This is now better understood: true cysts will not heal by conventional endodontic treatment. The rationale for performing an apicectomy has undergone a metamorphosis from being an alternative to conventional root canal treatment to an adjunct to root canal therapy. Major changes in techniques and materials are likely to improve success and change the role of the apicectomy procedure further.
We wish to thank Professor Brian Monteith for producing the drawings.
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Copyright: 13 August 2002
Correspondence: N.P. Chandler, Head of Discipline of Endodontics, Department of Oral Rehabilitation, School of Dentistry, University of Otago , PO Box 647, Dunedin,, New Zealand, Email: nick.chandler @stonebow.otago.ac.nz