Advancements in endodontic root-end surgeries

Dr. Jon Irelan discusses advancements in endodontic apical surgeries, driven in large part by microscopy

Stepping into the future

Similar to other procedures in medicine and dentistry, rapid advancements have been made in endodontic root-end surgery over the past few decades. Micro-CT has furthered our understanding of root canal anatomy and its complexity, while electron microscopy has shined light on the organization of tooth structure. An understanding of the histopathology of periapical disease and biofilms and the means by which they can be addressed have brought clarity to treatment planning and execution of care like never before.

Apical surgery has traditionally been geared toward addressing aberrant apical anatomy, including isthmuses and accessory canals, or in situations where apical canal anatomy has been obstructed. It is now understood that several etiological factors can lead to persistent apical periodontitis, which cannot be addressed with traditional orthograde endodontic treatment, including extraradicular infection, foreign body reactions, apical cysts, cholesterol crystals, and apical scarring.¹

In addition to becoming more knowledgeable about disease etiology, innovation has provided clinicians with the tools to improve the quality of care delivered. CBCT imagery allows for precise evaluation of each clinical situation and drives minimally invasive treatment planning. Marked enhancement in visualization with the aid of surgical microscopes and the ability to better perform the root-end preparation with ultrasonics have elevated success rates. While studies show traditional surgery without microscopy and ultrasonics garnered success rates ranging from roughly 19%-69%,^2-6 endodontists now enjoy success rates of roughly 87%-97%.^6-17 Despite root-end microsurgery now demonstrating a success rate that rivals most any dental or medical procedure, the perception among lay people and many dental professionals alike is that apical surgeries are reserved as a last-ditch effort.

A brief history

Early attempts to address periapical disease surgically can be dated back to the latter part of the 19th century, when dentists were offered an opportunity to ablate the periapical lesion in lieu of attempting to negotiate the tortuosity of the root canal system. As time progressed, root-end surgery was used as an adjunct for traditional orthograde endodontic treatment in situations where periapical healing was unsuccessful, and where perceived etiology could not be improved upon with orthograde retreatment. In addition to resecting a portion of the root-end, a root-end preparation and filling were later introduced. Using a dental handpiece and bur, a key slot prep was placed in the root-end followed by an amalgam or intermediate restorative material (IRM) restoration.

As the procedure evolved, success rates continued to improve. While the clinical situation could typically be improved upon by the surgeon, a large component of the procedure centered on providing the surgeon visual and physical access to the site. As a result, osteotomy sites remained sizable, and the root-end resection was performed at roughly 45 degrees to the long axis of the tooth to allow for visualization. The resultant bevel increased potential for unaddressed canal anatomy and the exaggerated exposure of dentinal tubules, which could allow for the transmission of bacteria.

In the 1990s and early 2000s, root-end surgery transformed from a traditional surgery into a microsurgical approach as the implementation of microscopy became more common place in endodontics. With microscopy, the armamentarium evolved to suit the newfound visual capabilities of the clinician, and with it, the procedure could be performed with a significant reduction to both the osteotomy size and taper of the root-end resection. These advancements, in addition to improved root-end filling materials like MTA^® and bioceramics, have allowed root-end microsurgery outcomes to become highly predictable.

Personal experiences

My practice is largely focused on endodontic retreatment and microsurgery, with roughly 50% of cases falling under either orthograde retreatment or apical microsurgery. With the majority of microsurgeries involving the treatment of molar teeth, ideal visualization of the surgical site is my main concern. This requires not only proper positioning of the patient, which allows him/her to remain comfortable throughout the procedure, but also the ability to maintain an ideal posture as the clinician throughout the surgery. My own surgical technique is centered around features offered by the ZEISS EXTARO^® 300. Mechanical features I appreciate in particular are the Mora Interface (Figure 1), the Foldable Tubes (Figure 2), and the strong emphasis on single-handed operation. With the Mora Interface, eyepieces are kept level, while the lens can be angled sharply to accommodate the patient’s position. While the Foldable Tubes are a lesser-known feature of the EXTARO, they allow the clinician to remain a greater distance from the scope in instances where the lens is angled back toward the clinician.

During surgery, I regularly employ methylene blue dye (Figure 3) for evaluation of root structure and apical anatomy, but I have also found fluorescence mode on the EXTARO 300 invaluable. While the fluorescence mode allows for the detection of cariogenic bacteria by exciting fluorophores that give off an orange-red light, I have personally found it to act as an excellent contrasting tool during microsurgery. Using this augmented visualization mode, dentin and cementum fluoresce brilliantly relative to osseous and soft tissue, allowing for ready identification and evaluation of the root structure (Figures 4 and 5).

Clinical case

While apical microsurgery has evolved from a standalone procedure into one that acts as an adjunct to satisfactory orthograde treatment, it can also offer a solution in challenging clinical situations where initial orthograde treatment is less than ideal.

In one such case, a 48-year-old female presented with a previously treated tooth No. 19. At the time of initial treatment by an endodontist, physical access to the MB canal was limited by a congenital jaw abnormality that greatly restricted opening and range of motion (Figure 6). Years later, the patient’s range of motion has been further limited by two invasive jaw surgeries. While tooth No. 19 had presented decoronated during initial treatment, it had since been restored with multiple fiber posts and a large zirconia crown. Now experiencing pain and swelling from an acute infection, the patient’s CBCT demonstrated a large radiolucency associated with the apices of tooth No. 19 in addition to vertical bone loss (Figure 7).

More definitive treatment options available included extraction or orthograde retreatment (both of which would have necessitated significant trauma to the temporomandibular joints) or apical microsurgery. With an understanding that orthograde retreatment or extraction might still be required if infection persisted, apical microsurgery was decided upon and rendered.

The patient enjoyed immediate post-operative relief and continued to return periodically for postoperative evaluation during the first year. Radiographs showed a progressive resolution of periapical and vertical bone loss noted in the preoperative CBCT, with the 1-year postoperative CBCT demonstrating a reorganization of the perio-dontal ligament structure of the root surface of tooth No. 19 (Figure 8).

Conclusion

The peer-reviewed literature strongly supports the viability of root-end microsurgery. While clinicians often have the opportunity to consider both orthograde and microsurgical retrograde treatments as options, many situations exist where root-end microsurgery offers the only means of maintaining the patient’s natural dentition. As such, it is vitally important that as stewards of endodontic treatment, we educate our patients and colleagues about the significant advancements made in endodontic microsurgery.