While endodontic microsurgery has been making tremendous strides in the past 20 years, there are still basic concepts that are confusing or frustrating for the novice and experienced surgeon alike. These issues, such as microscope positioning and the relationship with the surgeon’s ergonomics and line of sight to the surgical field, making use of natural hand movements and positions, are addressed in this article. Other topics include major flap designs and guidelines for their implementation, effective hemostasis using materials with less tissue toxicity, root end preparation techniques and guidelines, site-determined choice of root end filling material, and placement and finishing tips for Mineral Trioxide Aggregate.
In his book Working in a Small Place Mark Shelton chronicles the efforts of a young neurosurgeon, Dr Peter Jannetta, to introduce a radically new microsurgical technique for cranial nerve decompression. Pivotal to the technique was the use of the surgical operating microscope (SOM) for precise visualization and manipulation of the delicate structures. What Dr Jannetta discovered was that not only was the use of the SOM in neurosurgery a rare event but also this particular piece of armamentarium was regarded with disdain by the “Grand Old Men” of the profession. Programs were hesitant to implement this technology, and their residents were discouraged in its use because the senior staff members either felt estranged by the unfamiliarity with the SOM, or threatened by its presence. What Dr Jannetta realized was that, rather than trying to convince the grand old men of the merits of the SOM, he would work from within the system, slowly teaching his residents and wait for a new generation, his generation, to assume the role of senior staff members. He is quoted in the book as saying “It takes twenty years for anything new to really catch on, not because it takes that long to convince the establishment, but because it takes that long for there to be a changeover to people who have grown up with the new idea as being accepted.” Today, all residency programs in neurosurgery require proficiency with the SOM and microsurgery.
An interesting parallel is drawn when one examines the progression of the dental operating microscope (DOM) use in dentistry and, specifically, endodontics. Although presented as early as 1986 by Selden, it was not until the early 1990s that the DOM was introduced to the profession and graduate-level endodontic programs. The usefulness of the DOM in endodontics was viewed with similar skepticism by the senior attendings of most programs for all the same reasons of their counterparts in neurosurgery. However, a concerted effort was made by a few enlightened individuals with foresight enough to recognize the advantages that microscopy could afford, and they lobbied their cause until the late 1990s, when it was mandated that all graduate programs and students demonstrate a proficiency in the use of the DOM. Before 1999, only 52% of the endodontists surveyed reported using the DOM. Compare that to a more recent survey, in which the age of the operator was compared with their usage of the DOM and it was found that the younger respondents (35 years old or younger) used the DOM 97% of the time for surgical and nonsurgical treatment. It is clear that the recent graduates are not only more comfortable with its use, but are also more accustomed to rendering treatment with the DOM. What is an interesting coincidence is that endodontics is approaching the 20-year mark of the inception of the DOM into practice; it would seem that Dr Jannetta’s prophecies extend to the dental profession as well!
Although the basic principles of endodontic surgery have not been dramatically changed, advances in armamentarium and microtechniques have attempted to keep pace with the demands of today’s endodontic microsurgical environment: greater ergonomic flexibility, more efficient preparation and placement of the root end filling (REF), and more biocompatibility of the materials used.
Anesthesia and hemostasis
These 2 facets are inexorably linked because the effectiveness of the surgeon’s administration preoperatively not only influences the comfort of the patient during the procedure but also the control of hemorrhage at the surgical site. Standard protocol is divided into regional and local injections and are as follows:
The administration of a long-acting anesthetic agent such as bupivicaine (Marcaine) as a block technique to obtain a sustained level of anesthesia beyond the duration of the surgery. For posterior surgeries this entails, for maxillary sites, a posterior superior and middle superior alveolar block; for posterior mandibular sites, an inferior alveolar nerve block supplemented with a mental nerve trunk block. Maxillary anterior teeth are blocked using bilateral anterior superior alveolar or infraorbital injections, while mandibular anterior teeth receive bilateral mental nerve blocks. All of these can be supplemented, as need be, with corresponding palatal or lingual infiltrations of the same anesthetic.
In studies examining the effectiveness of lidocaine versus bupivicaine, it was shown that lidocaine was faster in onset of lip numbness while bupivicaine resulted in longer duration. However, Gordon and colleagues have shown that administration of bupivicaine following surgical extractions resulted in decreased pain for longer periods of time. By minimizing the peripheral barrage of peripheral nociceptive neurons, it reduced the development of central sensitization, thought to mediate partially the central component of allodynia and hyperalgesia. This postoperative effect can be further enhanced by the preoperative administration of a nonsteroidal anti-inflammatory drug, resulting in statistically less postoperative discomfort and delay of onset of pain. This peripheral block should be allowed to take effect (8–10 minutes) and signs of adequate anesthesia noted before the next phase.
Once regional anesthesia has been achieved, then a local infiltration of lidocaine 1:50,000 epinephrine is injected over the intended flap extent, concentrating the bulk of the infiltration over the surgical site. The injection speed is slow and steady (1–2 min/mL), allowing time for diffusion of the fluid and avoiding the formation of a bolus accumulating in the submucosa. Done correctly, blanching will be evident in the surrounding tissues, spreading throughout the flap and its perimeter. Care should be taken to avoid injecting into skeletal muscle. Doing so will activate the β-adrenergic receptors, triggering vasodilation instead of constriction, causing undue hemorrhage on flap reflection and subsequent limited visibility of the surgical site.
The outlined protocol is, of course, predicated on the systemic health of the patient and their ability to tolerate not only the surgical stress but also the cardiovascular impact of the epinephrine in the selected anesthetic. Even in healthy patients a transient tachycardia of short duration is not uncommon, but is usually well tolerated if the patient has been forewarned. However, in cases where underlying cardiovascular diseases such as uncontrolled hypertension or history of recent cardiac surgery place these patients at a higher risk, the surgeon would be prudent to consult with their physician before the procedure.