reading

To my parents, Arnie and Carol Schwartz, who supported and encouraged me. To my wife, Jeannette, who stood beside me all these years. And to my daughter, Marni, who has enriched my life as only a child can.
— RS

To my parents, teachers, and friends, and to the extraordinary clinicians on the TDO forum who inspired me to do this book. And to my wife, Mithuna, who encourages and supports me to follow my dreams.
— VC

I dedicate these illustrations to Nebraskans Wilma and Robert Fulk, without whom my entry into private practice would not have been possible; Wade Jensen, my favorite cousin, who has always believed in me; and Gary Carr, the founder of Pacific Endodontic Research Foundation (PERF) and The Digital Office (TDO), who created the environment for hundreds of us to become outstanding endodontists.
— TH

Best practices in endodontics : a desk reference / edited by Richard S. Schwartz and Venkat Canakapalli ; Illustrations by Anthony L. Horalek.

[DNLM: 1. Endodontics--methods--Handbooks. 2. Dental Pulp Diseases--therapy--Handbooks. 3. Root Canal Therapy--Handbooks. WU 49]

All rights reserved. This book or any part thereof may not be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, or otherwise, without prior written permission of the publisher.

36 Clinical Management of Teeth with Open Apices with the Apical Barrier Technique

Most accomplished clinicians credit much of their success to their mentors. All of the contributors to this book have benefitted from and acted as mentors. Over the past 15 years, the contributors have participated in an online discussion group as part of a virtual community of endodontists from around the world. All of us post cases for discussion, review research, collectively solve clinical problems, and learn from our long-term successes and failures. One day one of the members suggested that it would be nice if we could catalog and share some of this knowledge with a wider audience. That is the purpose of this book.

This book is “microscope centric” in the sense that all the contributors use a dental operating microscope for every patient. The procedures described in this book are best performed (and some can only be performed) under a dental operating microscope. Although endodontics can be performed without a microscope, a clinician’s level of care improves as microscope skills are acquired. The first five chapters are devoted to the microscope itself, including operatory design, photographic and video documentation of treatment, and how to do clinical procedures in the most efficient and ergonomic manner for the doctor and assistant. This material will be very useful to clinicians who are designing or remodeling an office and who want to document their work. It will be useful for both beginners and experienced clinicians and especially graduating residents.

This book is also “CBCT centric.” CBCT (cone beam computed tomography) is an integral part of the daily practice of all of the contributors. Two chapters are devoted to utilization of CBCT in endodontics, and it is integrated into the clinical chapters throughout the book. Several additional chapters on CBCT were originally planned for this book, but the amount of material grew to the point that a separate book is currently underway. It will contain material collected and organized in a manner that is not available anywhere else in the dental literature. It will be heavily referenced and will require several readings and “study” to gain an understanding of the benefits and pitfalls of CBCT and many of the common errors in interpretation.

The importance of recalls is emphasized throughout the book. Without long-term recalls, we are totally in the dark as to whether our treatments are successful. When recalls are included in the endodontic literature, they are rarely more than 2 or 3 years' follow-up. Recalls only start to become relevant in the 5- to 10-year time frame. We currently practice in the “implant era,” where relevant time frames have stretched out to 15- and 20-year measures of success and failure. A number of chapters are therefore devoted to restorative procedures, because in many cases, the restorative status of the tooth before and after endodontic treatment is the most important factor that determines longevity.

This book is designed to be a clinician’s guide in daily practice and is not a substitute for standard endodontic textbooks. It is not intended to be “scholarly” or “evidence based,” although some of the chapters are well referenced. Many of the chapters are devoted to a single procedure or topic and are written as how-to guides. Specific armamentaria and step-by-step instructions are included, and documented cases are used to illustrate specific principles. Chapters include practical information and “pearls” on a wide range of everyday clinical problems and scenarios. These chapters are intended to provide clinical guidance to clinicians performing unfamiliar procedures or wanting to learn alternatives to their usual approach. It is a book written by clinicians for clinicians, at a specialist level, but it is intended for anyone who wants to provide endodontic care at a high level.

The contributors to this book come from various backgrounds, geographic locations, and clinical areas of expertise. What they all share, however, is a specific vision of what the specialty of endodontics represents today and, more specifically, what an endodontist represents. In attempting to set the highest possible clinical standard for our specialty, we call upon all endodontists to join us in a re-examination of our core principles and a rededication to the vision that began this specialty more than 60 years ago.

The first part of this re-examination addresses the question: “What is endodontics?” The American Association of Endodontists answers this question with the following:

Endodontics is the branch of dentistry that is concerned with the morphology, physiology, and pathology of the human dental pulp and periradicular tissues. Its study and practice encompass the basic clinical sciences including biology of the normal pulp; the etiology, diagnosis, prevention and treatment of diseases and injuries of the pulp; and associated periradicular conditions.¹

This answer shapes and constrains the traditional view of clinicians and academics who consider the primary purpose of endodontic therapy to be the prevention or elimination of apical periodontitis “by means of cleaning, shaping, disinfecting, and filling the root canal system.”² This diseasecentric orientation dominates the priorities and directs the focus of our scientific research and scientific journals. It permeates our critical evaluation of clinical procedures and the procedural recommendations found in many textbooks for the broader dental audience.^3–15 It concludes that addressing the endodontic “triad” is the basis for successful endodontic treatment and forms the foundational basis of our specialty.^12,14–16

The contributors to this book view the purpose and end goal of endodontic treatment from a different perspective. We see endodontics as a branch of restorative dentistry whose primary purpose is the preservation of the natural dentition over the length of a patient’s life. Such a difference in vision is not merely pedantic in nature; it affects virtually every facet in the study of endodontics. Specifically, it affects how we make clinical decisions and how we interpret and measure our outcomes, and it establishes our procedural goals and recommended best practices. The assumed concordance of the goals of tooth preservation and disease elimination—assumptions that permeate our specialty—we view with increasing skepticism, and we suspect that these goals often operate at cross-purposes. Endodontics has fixated on clinical treatment objectives and end points directed toward removal of the pulpal remnants and bacteria that are believed to be the etiologic agents of endodontic disease. Thus, elimination of the causative agents of disease has become the objective of endodontic treatment.³ This focus often comes at the cost of competing considerations, which are at least as important for long-term tooth preservation, including structural and restorative considerations.

The key aspect of this discussion starts with a new answer to the question “What is a successful outcome?” Traditionally, endodontic outcome measures were diseasecentric, with disease being defined based on histologic critera.^17–19 Because we generally do not have histology available as an outcome measure, we rely on radiographic findings to determine the presence of apical periodontitis,^9,17 and the radiographic outcome is considered a primary measure of “success.”²⁰ Strindberg²¹ developed the initial definition of success in 1956, which included very stringent criteria, including radiographic re-establishment of a well-defined periodontal ligament. With the introduction of CBCT into endodontics, a new Periapical Index (PAI) based on CBCT was developed,²² which has continued this discussion.^23–26 These erroneous outcome measures have created problems for our specialty for decades that will not be improved by a CBCT-PAI. CBCT allows clinicians to identify even more “lesions” and “pathology” associated with teeth that have been free of clinical signs and symptoms for decades. Compounding this problem is that the majority of endodontic outcomes analysis counts death of the tooth as a good outcome because extracted teeth are excluded from the analysis. So ingrained in the clinician’s psyche is this radiographic measure of outcome that study designs that violate basic CONSORT guidelines are common, with little awareness of how skewed the analysis becomes. Therefore, we are not only studying the wrong outcome measure, but we are studying it incorrectly.

For these and other reasons, we draw a distinction between process-centered outcomes, clinician-/disease-centered outcomes, and patient-centered outcomes:

• Process-centered outcomes are the results of procedures the clinician performs. These include factors like the target parameters and end results of the cleaning, shaping, and obturation procedures and the radiographic appearance of the completed case. In many cases, process-centered outcomes have no relationship to clinician-/disease-centered outcomes or patient-centered outcomes, yet they make up the vast majority of articles in the endodontic literature.

• Clinician-/disease-centered outcomes are signs and findings that the clinician measures or observes as proximal evidence of treatment efficacy, or lack thereof. First among these is radiographic evidence of resolution of apical periodontitis (often inappropriately described as “healing of the lesion”). This outcome measure may or may not be related to the selected process-centered outcomes or to patient-centered outcomes.

• Patient-centered outcomes are outcomes that are relevant to patients.²⁷ They are outcomes that patients notice and care about, such as survival or loss of the tooth, normal function, symptoms such as pain or swelling, or health-related quality of life.²⁷ A test for patient-centeredness is the following question: “Were it to be the only thing that changed, would patients be willing to undergo a treatment with associated risk, cost, or inconvenience?”

Process-centered outcomes and clinician-/disease-centered outcomes are important, but only as they serve to help us improve or predict patient-centered out-comes.²⁸

The perspectives expressed throughout this book emphasize patient-centered outcomes. Our historical focus on processcentered outcomes and clinician-/disease-centered outcomes has misled us into studying the wrong outcome measures over an inappropriately short time frame. Much of this problem traces back to how we have defined endodontics and endodontic disease from the beginning.

When reading these chapters, please keep in mind that the primary goal of endodontic treatment is the long-term preservation of the dentition, not the lack of evidence of apical periodontitis. This lack of evidence of apical periodontitis, which is all a radiograph can show, is often mistaken for total elimination of disease (or evidence of health), based on the processes we infer are required to eliminate the disease. Obviously, all of us would wish to totally eliminate disease if we could; however, this is rarely possible in chronic disease states. Trying to achieve this goal by aggressive coronal and radicular preparations results in weakening of the tooth or, in some cases, premature loss of the tooth, with no real evidence that it results in a better “Strindberg result.” We must look at the larger picture and develop diagnostic and treatment protocols that better serve the goal of long-term tooth retention.

1. American Association of Endodontists. Specialty of Endodontics. http://www.aae.org/about-aae/specialty-of-endodontics.aspx. Accessed 28 January 2015.

2. American Association of Endodontists. Myths about Root Canals and Root Canal Pain. http://www.aae.org/patients/treatments-and-procedures/root-canals/myths-about-root-canals-and-root-canal-pain.aspx. Accessed 29 January 2015.

3. Paredes-Vieyra J, Enriquez F. Success rate of single-versus two-visit root canal treatment of teeth with apical periodontitis: A randomized controlled trial. J Endod 2012;38:1164– 1169.

4. Sedgley C, Nagel A, Hall D, Applegate B. Influence of irrigant needle depth in removing bioluminescent bacteria inoculated into instrumented root canals using real-time imaging in vitro. Int Endod J 2005;38:97–104.

5. Silva LA, Novaes AB Jr, de Oliveira RR, Nelson-Filho P, Santamaria M Jr, Silva RA. Antimicrobial photodynamic therapy for the treatment of teeth with apical periodontitis: A histopathological evaluation. J Endod 2012;38:360–366.

6. West J. Endodontic predictability: “What matters?” Dent Today 2013;32:108,110–113.

7. Siqueira JF Jr, Rôças IN. Clinical implications and microbiology of bacterial persistence after treatment procedures. J Endod 2008;34:1291–1301.

8. Fleming C, Litaker MS, Alley LW, Eleazer PD. Comparison of classic endodontic techniques versus contemporary techniques on endodontic treatment success. J Endod 2012;36:414–418.

9. Molander A, Warfvinge J, Reit C, Kvist T. Clinical and radiographic evaluation of one- and two-visit endodontic treatment of asymptomatic necrotic teeth with apical periodontitis: A randomized clinical trial. J Endod 2007;33:1145–1148.

10. Trope M, Bergenholtz G. Microbiological basis for endodontic treatment: Can a maximal outcome be achieved in one visit? Endod Topics 2002;1(1):40–53.

11. McGurkin-Smith R, Trope M, Caplan D, Sigurdsson A. Reduction of intracanal bacteria using GT rotary instrumentation, 5.25% NaOCl, EDTA, and Ca(OH)₂. J Endod 2005;31:359– 363.

12. American Association of Endodontists. Access Opening and Canal Location. Colleagues for Excellence, Spring 2010.

13. American Association of Endodontists. Root Canal Irrigants and Disinfectants. Colleagues for Excellence, Winter 2011.

17. Nair P, Sjögren U, Figdor D, Sudqvist G. Persistent periapical radiolucencies of root-filled human teeth, failed endodontic treatments, and periapical scars. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:617–627.

18. Nair PN. On the causes of persistent apical periodontitis: A review. Int Endod J 2006;39:249–281.

19. Paula-Silva FW, Wu MK, Leonardo MR, da Silva LA, Wesselink PR. Accuracy of periapical radiography and cone-beam computed tomography scans in diagnosing apical periodontitis using histopathological findings as a gold standard. J Endod 2009;35:1009–1012.

20. Saini H, Tewari S, Sangwan P, Duhan J, Gupta A. Effect of different apical preparation sizes on outcome of primary endodontic treatment: A randomized controlled trial. J Endod 2012;38:1309–1315.

21. Strindberg L. The dependence of the results of pulp therapy on certain factors. Acta Odontol Scand 1956;14(suppl 21): 1–175.

22. Estrela C, Bueno MR, Azevedo BC, Azevedo JR, Pécora JD. A new periapical index based on cone beam computed tomography. J Endod 2008;34:1325–1331.

23. Peters C, Peters O. Cone beam computed tomography and other imaging techniques in the determination of periapical healing. Endod Topics 2012;26:57–75.

24. Wu M, Wesselink P, Shemesh H. New terms for categorizing the outcome of root canal treatment. Int Endod J 2011;44:1079–1080.

25. Patel S, Mannocci F, Shemesh H, Wu MK, Wesselink L, Lambrechts P. Radiographs and CBCT—Time for a reassessment? Int Endod J 2011;44:887–888.

26. Liang Y, Li G, Wesselink PR, Wu MK. Endodontic outcome predictors identified with periapical radiographs and cone-beam computed tomography scans. J Endod 2011;37:326– 331.

27. PCORI Methodology Committee. The PCORI Methodology Report November 2013. http://www.pcori.org/assets/2013/11/PCORI-Methodology-Report.pdf. Accessed 29 January 2015.

28. Guyatt G, Rennie D, Meade MO, Cook DJ. Users’ Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice, ed 2. New York:McGraw-Hill Professional, 2008.

Before considering ergonomics and operatory design, we should clarify our ultimate objective. Briefly, in an ideal ergonomic practice, all procedures are performed under the microscope, even those that do not require a microscope to be performed competently. For example, screening a patient for oral cancer, administering anesthesia, and checking occlusion are procedures that are not typically thought to need magnification. The important question is not whether the microscope is required to perform a task but rather, in performing one set of tasks with the microscope and another set without it, is ergonomic efficiency negatively affected? The answer to that question is almost always “yes.”

Working in an environment where the microscope is constantly being moved into and out of the field is extremely inefficient and tends to be very distracting for the doctor, the assistant, and even the patient. Such a practice model fragments continuity of care, reduces focus on the task at hand, and often requires the use of Classes III, IV, and V motions (described later), thus dramatically decreasing both health and efficiency. For these reasons, we have come to understand that if the clinician can learn to incorporate ergonomic techniques and perform all procedures under the microscope—whether magnification is needed or not—then efficiency, focused concentration, competence, teamwork skills, and job satisfaction are all enhanced.

Ergonomics is the science of maximizing human performance and well-being and involves a study of both human excellence and health. Proper ergonomic design is necessary to prevent repetitive strain injuries and other musculoskeletal disorders, which can develop over time and lead to long-term disability. Box 1-1 summarizes the benefits of implementing ergonomic science into operatory design.

• Stress reduction

• Reduction in repetitive motion injuries

• Healthy posture

• Elimination of burnout

• Enhancement of clinical excellence

• Maintenance of optimal mental outlook

• Time-motion efficiency

• Healthy practice culture

• Elimination of disability

• Efficient office design

• Safety

• Performance consistency

• Retention of talented staff

• Reduction of fatigue

Ergonomic science classifies the kinds of motions required to perform a specific task. Generally, a task that can be completed using a single class of motion is more efficient than the same task performed with multiple classes of motion. For example, passing a mirror using just a Class I motion is far more efficient than using a combination of Classes I, II, III, IV, and V motions. Table 1-1 summarizes the classifications of motion, and there are several videos available on YouTube demonstrating how they impact efficiency and performance during endodontic procedures.¹

In endodontics, proper ergonomic design criteria are based on the goal of reducing Classes III, IV, and V motions while producing a healthy and injury-free environment where Class I and Class II motions predominate. With proper training, discipline, and teamwork, it is possible to perform nearly all endodontic procedures under a microscope using only Class I and Class II motions, with only an occasional need for Class III motion. Once this skill is mastered, the clinician will reap the benefits of increased productivity, heightened competence, stress reduction, postural balance, and an enhanced practice culture of focused teamwork.

Executing efficient ergonomics is a habit that is mastered through repetitive training. While bad habits are difficult to break once formed, good habits and proper technique can become part of routine practice in a short period of time. A clinician or an assistant can learn the required skills if there is effortful practice and a work environment conducive to learning and mastering a new skill set.

Operatory design and ergonomic technique go hand in hand. Even if the clinical team is practiced and wellversed in proper ergonomic skills, it is almost impossible to execute good ergonomic practice if the operatory does not reflect proper ergonomic design.

The circle of influence, a key principle in both operatory and front office design, posits that all instruments (ie, armamentaria, recordkeeping devices, viewing monitors) involved in the delivery of care should require nothing more than a Class III motion for both the doctor and the assistant (Fig 1-1). Employing such a principle places significant constraints on operatory and front office designs. Additionally, the operatory should be designed with sight angles so that there is little need to turn one’s head to view monitors, use keyboards, or procure accessory devices.

Fig 1-1 (a) Aerial view of the circle of influence design principle. View of the doctor’s (yellow circle) and the assistant’s (red circle) respective circles of influence. (b) The circle of influence design principle states that all required instruments and devices are within easy reach.

There are nine key elements that are required to realize good ergonomic operatory design (Table 1-2). The following sections describe each one briefly and discuss its role in ergonomics.

In order for the clinician to perform all dental procedures under a microscope, the lowest magnification should be not much over 2.2×. If the magnification is higher (ie, 3.5× or even 2.7×), it is difficult to complete certain procedures such as giving anesthesia, placing bands, prepping teeth, or performing an oral cancer examination, among others. If the practitioner adopts a model of practice where the scope is moved in and out of the operating field for different procedures and there is a continual changing of working positions, the result will be frustration and inefficiency and, ultimately, disappointment with microscope use. Lower productivity can be avoided if the microscope’s lowest magnification is 2.2×.

The ideal practice model is to bring the microscope into position at the start of a patient visit and never change that position until the procedure is completed.² We recommend a six-step microscope or a zoom microscope that has the capability of low-power magnification of 2.2× (Fig 1-2). At this magnification, the clinician can see from the floor of the nose to the bottom of the chin on most patients and is able to perform an oral examination, oral cancer screening, and occlusal examination provided he or she is able to move the patient chair effortlessly. Figures 1-3 and 1-4 demonstrate the circle of light range and the view seen at 2.2×. Clinicians using three-, four-, or five-step microscopes experience far more difficulty and typically revert back to a practice model where the microscope is used only for certain procedures, thereby guaranteeing inefficiency.

Fig 1-2 A six-step microscope with beam splitter, assistant’s scope, and camera.

In observing hundreds of endodontists over a 20-year period, the author has concluded that one of the most significant impediments to good ergonomic technique involves poor patient positioning and chair ergonomics.

The secret to working effectively under the microscope is to move the patient chair, not the microscope. Nearly all endodontic procedures are performed with the patient in the Trendelenburg position, in which the patient is in the supine position with the feet higher than the head by 15 to 30 degrees. It is seldom necessary to change the patient from this position, whether you are working on the maxilla or the mandible or performing surgical endodontics. What the clinician needs is to be able to move the patient chair laterally in an eastwest direction with either the knees or the legs while working under the microscope. For such motion to happen effortlessly requires a patient chair that “floats” freely, so the microscope itself rarely needs to be touched other than to change magnifications or make small adjustments in focus.

What may not be evident to all clinicians is that nearly all endodontic procedures have a natural procedural flow to them, and the skillfulness required for these procedures is affected adversely by even minute interruptions or fragmentation. Preventing this fragmentation by moving the chair instead of the microscope eliminates such interruptions and allows one to work continuously with total focus on the procedure itself and not on the tool being used to perform the procedure.

A second factor concerning the patient chair is the size and location of the chair headrest. The headrest is almost always a problem for the endodontist performing all procedures under the microscope. With most headrests, the patient’s head cannot be positioned close to the doctor’s lap, and the doctor will be required to bend forward at the waist (a Class V motion), creating back, neck, and shoulder stress. Patient chairs with removable headrests are far more preferable. Head and neck comfort for the patient can easily be provided by a Tempur-Pedic pillow placed underneath the head and shoulders (Fig 1-5) while allowing the patient’s head to be correctly positioned in the doctor’s lap (Fig 1-6). Figures 1-7 and 1-8 compare the changes in positioning required with the standard chair headrest and the removable headrest.

Fig 1-5 (a) Pillow placement replacing the chair headrest. (b) Pillow placement to support the neck.

Fig 1-7 (a and b) Headrest prevents proper patient positioning and requires bending from the waist.

Fig 1-8 (a) Headrest removed. Notice the upright position of the operator. (b) Close-up view of the patient with the headrest removed and the operator in an upright position.

The incidence of disability claims for both doctors and assistants is surprisingly high. A Dutch study³ reports that nearly half of all dentists will experience a disability that will prevent them from working at full capacity during their career. Similarly, almost 90% of dentists will suffer from some physical impairment of their back, neck, shoulder, arm, or wrist during their productive career that will impact their practice significantly. Therefore, proper posture and sitting positions are imperative in microscopic endodontics. Repetitive motion injuries are common, and it is rare to find an endodontist or assistant who has practiced for more than 10 years who does not have some type of physical problem with the neck, back, shoulder, or wrist. All of these injuries affect job performance and job satisfaction/fulfillment, increase working stress, and bring significant economic repercussions. Although repetitive stress injuries are complex in both their origin and course, all healthy ergonomic technique starts with correct posture and sitting positions, so it is imperative to pay attention to how one sits and positions oneself while working.

With correct posture and positioning at the microscope, it is possible to work in such a way where your postural support muscles are relaxed and at rest (Fig 1-9). Dual (ie, right and left), movable armrests are critical for both the doctor and the assistant, and their correct use can completely eliminate shoulder and neck pain that is caused by spasms of the trapezius and sternocleidomastoid muscles. Because an assistant is required to have both right- and left-handed skills, having armrests appropriately positioned for the assistant is crucial (Fig 1-10). The standard half-circle armrest found on most assistant stools is a very poor choice because it forces the assistant to be too far away from both the doctor and the assistant microscope and makes erect posture impossible, thus necessitating a Class V motion (bending at the waist) (Fig 1-11).

Fig 1-11 (a) Improper assistant’s chair with forced bending at the waist. (b) Healthy, upright sitting position and relaxed posture for the assistant.

Because accurate suctioning is fundamental to competent assisting, it is important for an assistant to be able to perform this procedure erect and without muscular stress. In Fig 1-12, the assistant uses her left hand, with elbow on the armrest, to accurately position the suction tip. The handgrip used to hold the suction device also deserves attention, as it is important to avoid stressful pronation of the wrist typically experienced by assistants performing suctioning on patients. Bending and twisting during assisting is one of the primary drivers of assistant injury and may very well be one of the major factors in assistant burnout. If assistants are physically fatigued from bending and twisting all day and return to their families at night physically exhausted, it will inevitably have a negative impact on job satisfaction and talent retention.

Fig 1-12 (a and b) Assistant suctioning position using the left hand from two viewing angles. (c and d) Proper hand position to eliminate fatigue.

Extreme accuracy in suction placement plays an important role in defogging the mirror and avoiding water-spray splash from the handpiece (Fig 1-13) in all phases of endodontics, including conventional retreatment, and surgical endodontics where the ability to see cannot be compromised. Often clinicians are not aware of the increase in efficiency achieved by simply having accurate suction placement by their assistant. Even the distance of as little as 1 or 2 mm can make all the difference between a mirror that stays debris- and splash-free and one that does not.

Fig 1-13 (a and b) Improper suction and mirror placement with resultant mirror splash. (c and d) Proper mirror and suction placement that minimizes mirror splash. Notice how far away the mirror is placed from the site and where the suction tip is placed.

The dental operatory is a confined space, and it requires careful planning to develop an effective ergonomic design. Because microscopes do not function well when they are used at the maximum extension of their arms, careful measurements need to be taken to ensure that the operator always has some degree of freedom of positional movement of the microscope. Patients vary in height and size, and an improper mounting can make treating patients outside the normal range difficult and uncomfortable.

The choices for microscope mounting include floor, wall, and ceiling mounts. Floor mounts are very problematic for a variety of reasons mostly having to do with the restriction of patient access to and from the chair as well as restriction of the east-west rotational movement of the chair. If new construction is contemplated, the ceiling mount is far more preferable because access to the microscope from the doctor’s side should require no more than a Class IV motion (Fig 1-14).

Fig 1-14 (a) Microscope placement requiring only a Class IV motion to bring it into use. (b) Ceiling mount.

Ceiling mounts over the patient’s right or left hip position are less desirable than a rear-mounted ceiling location. The hip-mounted location can impede a patient’s ingress or egress to the chair and may present a hazard, causing a patient to potentially strike their head against the microscope if they stand up too quickly. This problem is not present with rear-mounted installations.

The microscope’s range of motion, both vertically and horizontally, needs to be considered during mounting. The microscope should not be mounted so that it is ever needed at the maximum range of its extension arms. The author prefers the rear back wall or rear ceiling mount both for its ease of installation and ease of moving it into and out of the operating field (Figs 1-15 to 1-17.

Assistant/co-observation tubes (or scopes) are one of the greatest advantages of parallel-optics microscopes. A co-observation tube is attached to the beam splitter on the microscope, and a properly configured assistant’s scope allows the assistant to sit in an ideal upright position, always muscularly at rest for all endodontic procedures including surgical endodontics. The advantage of this approach should not be taken lightly, and endodontists who take the time to train their assistants in this technique never return to using a microscope that does not have a co-observation scope.

The configuration of the assistant’s scope is critical. It must be a dual-axis (not single-axis) scope that utilizes two degrees of freedom around two separate axes (Fig 1-18). It must also have inclinable binoculars, not fixed binoculars (Fig 1-19). If the co-observation scope is not configured properly, the assistant will not be able to achieve the ideal ergonomic sitting position for every procedure. Single-axis assistant scopes are to be avoided, as are fixed-angle binoculars, because these handicap the assistant ergonomically and will greatly compromise the assistant’s ability to function at a high level.

Fig 1-19 (a) Dual-axis and inclinable binoculars on an assistant scope. (b) Range of motion of inclinable binoculars.

Many clinicians have a difficult time understanding the benefits of a co-observation scope. However, there are many advantages of a co-observation scope in endodontics: (1) enhanced teamwork and practice focus; (2) increased clinical competence; (3) increased efficiency; (4) retention of top assisting talent; (5) less guesswork on the part of the assistant; (6) preservation of the ergonomic health of the assistant; (7) more accuracy in the performance of critical assistant functions; and (8) promotion of a practice culture centered around clinical excellence.

Dental delivery units have their own ergonomic constraints for the endodontist who performs all procedures under a microscope. The common methods of dental delivery systems used in endodontics—rear delivery or over the patient—are very poor models for the microscopic approach. The circle of influence principle and the need to minimize the frequency of Classes III, IV, and V motions demand a mobile cart system delivered from the front side of the operator. It is imperative that the clinician not reach for handpieces, ultrasonics, or Stropko Irrigators (SybronEndo) in a way that requires any motion from the shoulder or any motion that requires lifting of the elbow off the chair armrest. The delivery cart should be easily positioned so that a single Class III motion is all that is needed to grasp any required device (Fig 1-20). Having a self-contained water supply and onboard compressor makes the cart even easier to move and minimizes the contents of the connecting umbilicus (Fig 1-21).

Fig 1-20 (a) Positioning of the doctor cart for Class III motions. (b) Class III motion to the doctor cart.

Element	Requirement
Microscope parameters	Six-step or zoom with lowest magnification down to 2.2×
Patient chair and headrest	Must be freely movable (rotation) and without a headrest
Doctor and assistant stools	Dual adjustable (height and angle) armrests, adjustable lumbar support
Microscope mounting	Wall, ceiling, floor mounts
Assistant/co-observation scope	Adjustable, dual-axis (not single-axis) co-observation tube with inclinable binoculars
Doctor cart or delivery system	Freely movable with internal water supply and compressor
Back wall design	Self-contained assistant’s platform and storage as well as suction
Assistant monitor	Viewable from the assistant’s working position
Doctor monitor	Viewable from both the doctor’s and the assistant’s working position

Class I	Moving only the fingers
Class II	Movement from the wrist
Class III	Movement from the elbow
Class IV	Movement from the shoulder
Class V	Movement from the waist