Modern Apical Microsurgery

Recurrent endodontic pathosis, otherwise known as posttreatment apical periodontitis, presents clinically as the persistence or recurrence of symptoms or radiographic findings. These treatment failures may be related to persistent root canal infections wherein the primary endodontic infection continues or to secondary infections wherein reinfection of the previously treated space occurs.^1,3 For root canal therapy to be successful, both thorough disinfection and obturation of the root canal spaces must be completed. Persistent infections may be caused by bacteria that evade disinfectants within isthmuses, dentinal tubules, or initially untreated anatomy. Endodontic treatment of poor quality (ie, poorly cleaned or obturated canals) increases the incidence of endodontic failure by 65%.³ The endodontic literature regularly demonstrates that procedural errors such as perforation or instrument separation do not lead to failure of root canal therapy if managed appropriately. However, if unrecognized or unmanaged, these errors may lead to the development of recurrent endodontic pathosis.³ Infections may also persist in the periradicular area because of the development of extraradicular biofilm. Long-standing intracanal infections can spread into the periapex and form a thick and mineralized biofilm similar to calculus, which is unable to be eradicated by primary endodontic therapy.⁴

Secondary infections (ie, the reinfection of previously treated root canal spaces) are often associated with coronal leakage, which permits the ingress of oral microbes into root canal spaces. Coronal leakage can occur when temporary restorations are left in place beyond their usable lifespan or when poorly fitted definitive restorations are placed on endodontically treated teeth. During any root canal therapy, an impermeable seal is fundamental to ensuring the success of treatment because bacteria can spread to the periapex along exposed endodontic obturation material in as little as 3 days.³

The diagnosis of recurrent endodontic pathosis does not doom teeth to extraction; many may be candidates for nonsurgical (ie, orthograde) re-treatment or endodontic microsurgery. Apical microsurgery, specifically, entails root-end resection, apical curettage, and placement of a root-end filling in a diseased tooth.⁵ Endodontic microsurgery offers patients predictable outcomes for the management of posttreatment apical periodontitis. With appropriate case selection and the use of modern techniques, this therapy can achieve success rates of 96.8% after 1 year and 91.5% after 7 years.² Stated differently, apical microsurgery allows clinicians to maintain 91.5% of teeth that exhibit recurrent apical periodontitis.

A patient presented with swelling apical to both teeth Nos. 13 and 14 (Figure 1). The dental history revealed that endodontic treatment had recently been performed on both teeth and that a large post had been placed in tooth No. 13. Apical microsurgery was performed on both teeth, and perforating apical lesions were noted on both tooth No. 13 and the mesiobuccal root of tooth No. 14. Under microscopy, a root-end resection and ultrasonic retropreparation were performed and root repair putty (EndoSequence^® BC Root Repair Material Putty, Brassler USA) was placed (Figure 2). At a 2-year follow-up appointment, the patient was asymptomatic and healing was noted radiograpically (Figure 3).

Outcomes have improved significantly with the modernization of surgical techniques. Traditional surgery, which used little to no magnification, bur preparation, and amalgam or intermediate restorative material (IRM) retrofills, was associated with markedly unpredictable outcomes. When comparing the outcomes of traditional and modern techniques, one study found that the use of traditional surgical techniques demonstrated success rates of approximately 59% whereas more modern approaches demonstrated success rates of about 94%.⁶ Modern endodontic surgery incorporates several technological advancements, including CBCT imaging, surgical microscopy, ultrasonic preparation, and bioceramic filling materials. There are immediately visible radiographic differences between traditional (Figure 4) and modern surgical approaches (Figure 5). In the radiograph depicting the traditional surgical approach, note the uneven apical resection on tooth No. 10, the wide retropreparation of the canal space that was performed with a bur, and amalgam fill within the apex (Figure 4). Modern surgical approaches, like those depicted in the radiograph of the treatment of tooth No. 13, facilitate even resection at a minimal bevel and employ retropreparations that better conform to the existing canal spaces (Figure 5). Consequently, the root retrofills appear as an extension of the existing root canal fillings.

Three-dimensional imaging modalities such as CBCT allow clinicians to better diagnose endodontic pathoses and to subsequently plan surgical interventions. These images can determine the exact location and extent of a periapical lesion as well as the presence or absence of pathosis on other roots of the tooth, providing a roadmap for procedural success. In addition, CBCT facilitates direct visualization of adjacent critical anatomy, such as the maxillary sinus, the inferior alveolar nerve canal, and other important structures.⁷

Similar to the use of CBCT, the use of the surgical operating microscope has led to significant improvement in the delivery of endodontic treatment and has had a direct, positive influence on the outcomes of endodontic microsurgery.⁷ The microscope not only allows for magnification but also enhanced illumination, which optimizes visualization. Microfractures, accessory canals, and isthmuses between teeth can be easily identified.⁶ Use of the microscope allows for clear visualization in smaller areas, permitting clinicians to resect the root apex at a shallower bevel. And because shallow bevels require less root structure to be removed, microsurgical techniques facilitate the conservation of root structure and improved crown-to-root ratios.⁸ According to the results of a systematic literature review, surgical cases that used magnification from microscopes or endoscopes in combination with bioceramic materials, such as mineral trioxide aggregate (MTA), exhibited better outcomes than traditional methods that used loupes and other retrofilling materials.⁹ Better visualization leads to better care delivery and, consequently, more predictable outcomes.

Ultrasonic instrumentation has vastly improved both root resection and retropreparation.⁷ Historically, micro-handpieces (ie, mini burs) were used, but they were associated with the development of cracks and fractures in adjacent roots.⁸ The advent of ultrasonic instrumentation has directly reduced the development of dentinal fracture.⁵ Ultrasonic instruments vary in shape and possess a variety of angled tips that enhance access into the prepared root structure, permitting more individualized care.⁸ Moreover, ultrasonic instruments facilitate deeper retropreparations and can better clean complex canal anatomy, such as isthmuses between canals. When used in combination with a surgical operating microscope, ultrasonic handpieces allow clinicians to maintain smaller osteotomy sizes while removing the full extent of apical lesions. Beyond the obvious effects of conserving bone, the smaller crypt sizes that result from this treatment have been associated with better outcomes in endodontic microsurgery cases.¹⁰

In addition to these other advances, bio-ceramic root-end filling materials have significantly improved the outcomes of apical microsurgery. Traditional surgical techniques often utilized IRM, super ethoxybenzoic acid, or amalgam for root-end fillings. These materials were associated with leakage and significantly poorer outcomes when compared with newer materials.⁵ Bioceramic retrofill materials include products such as MTA (MTA Flow^™, Ultradent Products, Inc.), root repair putty, and dentin replacement material (Biodentine^®, Septodont USA). MTA shows superiority to amalgam in terms of its sealing ability and its biocompatibility. It goes beyond repair to facilitate the regeneration of periradicular tissue. In fact, normal periodontal ligament structures are shown to directly attach to these materials. In addition, MTA is bactericidal and fungicidal; produces a high pH environment, which not only inhibits bacterial growth but also osteoclastic activity; and sets in the presence of moisture, including blood contamination.⁵ The downsides to MTA are that it must be freshly mixed and that it can be difficult to handle and manipulate.⁵ Root repair putty has proven to be a formidable alternative to MTA because it is premixed and designed to overcome the difficult handling characteristics of MTA. It has also been shown to possess comparable properties when compared with MTA.¹¹ Dentin replacement material provides another reasonable alternative to MTA. It takes approximately 2 weeks to fully set after the initial setting, but it provides high compression and flexural strength as it undergoes transformation into a denser material with decreased porosity.¹² The technologic advances associated with more predictable outcomes in apical microsurgery are summarized in Figure 6.

Recurrent or persistent apical periodontitis no longer necessitates the extraction of the diseased dentition. Advances in surgical technology and techniques have provided clinicians with additional options to treat recurrent or persistent disease. Advances essential to achieving positive outcomes following surgery include the use of preoperative CBCT imaging, a surgical operating microscope, ultrasonic instrumentation, and bioceramic root-end retrofilling materials. Given the enhanced predictability of surgical outcomes using these modern techniques, practitioners should be aware of the procedural changes, and patients should be informed of the exciting and updated means available to save their teeth.

Alisha Desai
Harvard School of Dental Medicine
Boston, Massachusetts

Rebekah Lucier Pryles, DMD
Upper Valley Endodontics
White River Junction, Vermont
Assistant Clinical Professor
Department of Endodontics
Tufts University
School of Dental Medicine
Boston, Massachusetts

Brooke Blicher, DMD
Upper Valley Endodontics
White River Junction, Vermont
Assistant Clinical Professor
Department of Endodontics
Tufts University
School of Dental Medicine
Boston, Massachusetts
Clinical Instructor
Department of Restorative Dentistry and Biomaterials Science
Harvard School of Dental Medicine
Boston, Massachusetts

Jarshen Lin, DDS
Director of Predoctoral Endodontics
Department of Restorative Dentistry and Biomaterials Science
Harvard School of Dental Medicine
Boston, Massachusetts
Clinical Associate
Department of Oral and
Maxillofacial Surgery
Massachusetts General Hospital
Boston, Massachusetts