In part one of this 2 part series, I will discuss basic factors for why magniﬁcation alternatives might be considered by all practitioners regardless of age or visual acuity, as well as looking at resolution of the native human eye, the Magniﬁcation Continuum, and an overview of magniﬁcation alternatives in private practice. Part 2 will look at the advantages of using telescopic loupes in dentistry, and conclude with the 4 advantages of using the operating microscope in dentistry.
In the last 2 decades, technology has changed dentistry in nearly all areas, including armamentarium, materials, and techniques.1-5 Patients are living longer and want to maintain their dentition throughout life. In addition, patients are now more knowledgeable about options for improving their smile cosmetically and replacing missing teeth through dental implants. Technology has given clinicians marvelous new options to create healthy and attractive smiles as long as microscopic attention to detail in both the use of materials and the techniques necessary to provide excellence are observed. Clinicians must now focus on how to provide dentistry that is not only functional but aesthetically exceptional, keeping with the principles of minimal or, in some cases, no intervention at all.6-8 The rise in technological advances in dentistry, combined within increased expectations and demands from patients for long-lasting “invisible white restorations,” can create challenges for even the most detail-oriented dentists.9-11
The increasing demand by today’s dental patients for these aesthetic, conservative, and durable restorations requires that the clinician be able to visualize the operating ﬁeld in much greater detail. The ﬁeld of medicine has long advocated the use of magniﬁcation for aiding in delicate procedures. Medical disciplines such as otolaryngology, neurology, and more recently, acute care, have embraced magniﬁcation for surgery as well as delicate procedures such as reanastomoses of severed appendages. Our medical colleagues have relied upon enhanced visual acuity to improve treatment outcomes for many years.12-18
The use of magniﬁcation by general dentists in dentistry has been slow in its growth. The concept that magniﬁcation was mainly needed by “mature” practitioners whose eyesight was failing, was generated for many of us in dental school.19 During our education, some of the instructors wore magniﬁcation of some sort and, many times in the 1980s, it was simple single lens clip-on magniﬁers. After the age of 45 years, presbyopia (the inability to focus sharply on close objects) occurs naturally. In order to see objects that are closer than 6 m clearly, the ciliary muscles of the eye must contract or relax to change the ocular lens thickness.20 With time, through deterioration of the muscles of the eye and a loss of elasticity of the lens of the eye, it becomes more difﬁcult for many dentists older than age 45 years to focus on close objects. Despite this fact, it is interesting to note that many dental faculties and dental hygiene schools are currently requiring their youthful students to purchase magniﬁcation as part of their armamentarium, since it is now understood that magnification can help improve ergonomics and treatment outcomes.21-22 Further, it has been understood that magniﬁcation can be a useful tool during the teaching process itself,23 and, although there are some issues in getting all faculty members to embrace the value of magniﬁcation,24 a growing number of dental schools and dental hygiene programs are embracing magniﬁcation as being an important in the education process in dentistry.25-26
The use of surgical telescopes (loupes), from a rarity to the norm in general practice, increased dramatically from 1980 to 2001. In the author’s home province of British Columbia, the percentage of clinicians using any form of magniﬁcation rose from 20% in 1986 to 75% in 2000.27-28 During the past decade, the growth of high levels of magniﬁcation (dental operating microscopes) has continued to climb in endodontics. In 1999, one survey found 52% of endodontists had access to and used an operating microscope, and most of the time it was used for difﬁcult treatments where high levels of magniﬁcation were required, such as separated instruments, root-end preparations, and root-end ﬁllings.29 In 2008, a similar survey found that 90% of endodontists in the United States had access to and used the operating microscope in their practice, in a similar fashion to the study from 1999, but with a greater number using it for locating canal oriﬁces.30 So, it appears that there is a growing interest in all levels of magniﬁcation. This article will discuss reasons for incorporating magniﬁcation into your practice, and the alternatives, beneﬁts, and challenges that exist in this journey.
Resolution of the Human Eye and Visual Information
Carr,31 in his landmark article, cited research from the medical literature which showed that the human eye, when unaided by magniﬁcation, has the ability to resolve or distinguish 2 distinct lines/objects that are separated by a minimum distance of 200 µm (0.2 mm). When these lines or objects are closer together than 200 µm (0.2 mm), the human eye will see them as a single entity.
|Figure 1. The 2.5x ﬂip-up loupes.||Figure 2. The 4.5x through-the-lens (TTL) loupes with headlight.|
When we add magniﬁcation to the equation, the clinician is able to see in much greater detail than what is possible with the eye alone. For example, 2.5x magniﬁers (such as entry level telescopic loupes, as shown in Figure 1) improve the resolution of the human eye from 200 µm to 80 µm, and medium range magniﬁcation of 4.5x (Figure 2) telescopic loupes improve the resolution of the human eye to 44 µm, or 0.044 mm (Table 1).
Baldessara et al32 concluded that a skilled, trained clinician with a sharp, new explorer could determine marginal gaps in the range of 35 µm to 50 µm. It is therefore possible to conclude, that at levels above 4x to 6x magniﬁcation, the dependence on tactile cues (using explorers) might be replaced with a greater reliance on visual cues. It is interesting to note that a dental operating microscope at 20x power will provide a resolution of 10 µm (a human hair is approximately 50 µm in width).
Some clinicians are surprised as to how much more they “see” when they increase the amount of magniﬁcation they are using. The amount of visual information that is provided to the clinician is in fact the area of the surgical site (x axis times y axis) and is indicative of the power of increasingly higher levels of magniﬁcation. Table 2 and Figure 3 show the impact that higher levels of magniﬁers have on the amount of visual information that is provided.
On closer inspection, one can see that increasing magniﬁcation from 2x loupes to 4x loupes will not just provide double what you can see, but in fact provides a 4-fold increase in the amount of visual information available. Correspondingly, when an operating microscope is used at 12x magniﬁcation, then the amount of visual information provided is 24x what is seen with 2x loupes. As the clinician begins to understand how seeing better may mean better treatment outcomes, routine use of magniﬁcation in daily practice becomes a necessity, not a luxury.
There are 3 basic magniﬁcation systems available in dentistry for surgical telescopes; these include single lens, Galilean loupes, and prismatic (Keplerian) loupes.20
Single lens loupes (Amsted) are the simplest form of magniﬁcation and are low-powered, clip-on magnifying lenses that attach to glasses or a headband. They are inexpensive solutions, but have limited magniﬁcation (up to about 3x), and limited depth and diameter of ﬁeld of vision.
Galilean loupes are used for 2x to 2.5x magniﬁcation in that they use 2 or more lenses to focus the image. The systems are more expensive than single lens loupes and although the level of magniﬁcation is limited, the depth and diameter of the ﬁeld of view as well as the resolution of the image are improved (Figure 1). Often this level of magniﬁcation is desirable for someone just beginning a journey into magniﬁcation, as it is easier to learn to use, lighter in weight, and does not require additional illumination in most instances.
Finally, prismatic (Keplerian) loupes have multiple lenses (around 5 as well as 2 prisms) to focus the image and give greater clarity. The price is more expensive to make these, and the lenses are larger and heavier, resulting in a smaller depth of ﬁeld as the magniﬁcation increases (Figure 2).
When choosing loupes, a clinician should look at the magniﬁcation of the system and choose one that initially will provide the greatest chance of adaptation (ie, 2x to 3x loupes is the most often suggested initial magniﬁcation). In addition, one should also consider the ﬁeld width, depth of ﬁeld, as well as whether he or she would like to ﬂip up the loupes for an unmagniﬁed assessment of the ﬁeld of view. These “ﬂip-up” loupes typically are bulkier and heavier than their through-the-lens (TTL) counterparts and can easily go out of adjustment; this can affect the view that you have (double image), and also your posture. The ability of TTL loupes to be mounted directly into a prescription lens does necessitate repair anytime that the prescription changes. Furthermore, TTL loupes can only be mounted at an angle up to about 45° (called the declination angle) from horizontal. The heavier the Keplerian loupes are, the greater is the tendency for the loupes to want to ride down the nose; and the greater is the need for a strap that ﬁts tight around the back of the head to hold the loupes tight.
|Figure 3. The relationship between magniﬁcation and the amount of visual information seen by the retina.|
|Figure 4. The Magnification Continuum, as proposed in 2001 by the author.|
|Figure 5. The 2013 version of the Magniﬁcation Continuum.|
The ideal working distance is an important consideration when purchasing a new set of loupes, and can be adjusted with most systems. The working distance variation can be set for operators who like to lean closer to the operating ﬁeld (near focal distance), all the way up to those who like to sit upright and at a further distance away from the surgical site. Under ideal circumstances, the latter situation (sitting in a more upright fashion) is better from an ergonomic standpoint as the operator will have less fatigue in both the lower (back) and upper spine (neck and shoulders). It is nearly impossible for any set of loupes to achieve a straight forward vision (as can be obtained with the operating microscope), and, if neck and back pain are severe for a dentist or a hygienist, an operating microscope may lessen the severity of the pain if the microscope is properly adjusted.
In 2001, I described the term Magniﬁcation Continuum to try to deﬁne the growing number of magniﬁcation users who were progressing through increasing powers of magniﬁcation.33 Through personal experience derived from my lectures and discussions with other dentists, I had discovered that a growing number of clinicians were using magniﬁcation routinely in their dental practice. Some of these clinicians were just beginning their journey into enhanced visual acuity, while others had been using loupes for many years. In fact, it was not uncommon to hear of dentists who had several different sets of magniﬁers ranging from low-level 2.0x to 2.5x loupes through to 6x loupes with a headlamp. In many instances, with experienced clinicians, there seems to be waves of progression forward to higher and higher levels of magniﬁcation throughout time. It seemed that, as the appreciation for the value of magniﬁcation matched the level of expertise with the increased level of magniﬁcation being used, clinicians would often look to add a new magniﬁcation to their armamentariums. In addition, some clinicians were opting to use dental operating microscopes that had multiple levels of magniﬁcation (2x to 20x power). These clinicians were often focusing on disciplines such as endodontics or cosmetics, where magniﬁcation and illumination could help with details such as discovery of pulpal anatomy, or with nuances in preparation design and marginalization; details that could enhance the ﬁnal treatment aesthetically, as in the case of cosmetic dentistry (Figure 4).
Twelve years after this initial idea surfaced, the author has revised his original concept to include 2 to 3 phases of magniﬁcation progression (Figure 5). The entry-level power of 2.0x to 2.5x magniﬁcation is what many dental hygienists and dental students are still being exposed to during their education. This lower-level-magnification introduction is also the suggested starting point for many more-experienced clinicians looking for a solution for presbyopia, to improve clinical results, and/or to aid with neck and back pain. During this initial phase, the clinician will encounter a learning curve (A, Figure 5) that often takes from a week to a month. During this period, the clinician will at times ﬂuctuate among using the loupes for endodontics, cosmetics, root tip extractions, crown preparations, or other procedures, but may also provide treatment without them. After one or 2 more periods of sustained use with shorter learning curves (B, Figure 5) ,the clinician will use them full-time for most procedures and, at times, question how he or she ever did dentistry without magnification!
It is with regular use and time that the clinician may eventually seek out higher powers of magniﬁcation (C, Figure 5) and at this point enter into one’s second and eventually even third set of loupes. Initially some practitioners may envision using only the new medium powered loupes (eg, 3.5x magniﬁcation) for endodontics or during difﬁcult to visualize procedures (D, Figure 5), and they may then ﬂuctuate between the low and medium powers as the procedure dictates. With time, dentists may then reach a period where they are seldom using the lower power and using only the more recent purchase (E, Figure 5). At times, clinicians will choose another higher magniﬁcation again and, in addition, incorporate a headlamp (often needed above 3.5x mag); now they will have 2 to 3 different sets of loupes with a headlamp (F, Figure 5).
If the clinician enjoys endodontics and wants multiple powers of magniﬁcation (without changing loupes) and coaxial shadow-free illumination while, at the same time, easing documentation of procedures, a dental operating microscope (Global Surgical, Carl Zeiss Meditec, Leica Microsystems, or Seiler Precision Microscopes, for example), or heads up display system (MagnaVu [Magnified Video Dentistry]) offer the ultimate in higher levels of magniﬁcation.
These systems involve a new learning curve, requiring that the clinician learn how to reposition the patient or the patient’s head. In addition, these systems require a greater dependence on indirect vision (intraoral mirrors) in both arches in order to optimize the view. This contrasts with positioning in loupes-based dentistry, where the operator frequently must reposition while the patient remains stationary (G, Figure 5). This learning period can be anywhere from a month to a year, depending on the dentist. However, the operator will eventually learn how to use all magniﬁcations of the system from low to high power. After several phases of using the lower powers of the microscope only (H, Figure 5), the clinician will learn how to operate throughout the ranges of magniﬁcation. In time, he or she will be able to work comfortably at most of the magniﬁcations available, as dictated by the procedure, patient, and the challenges thus created for the clinician (I, Figure 5).
|Figure 6. Loupes vision versus microscope vision. |
Slide courtesy of Dr. David Clark, Tacoma, Wash.
|Figure 7. The author progressed from 2.5x ﬂip-up loupes (SurgiTel) to 3.5x flip-up loupes (Keeler Instruments) and, eventually, to the 4.5x extended ﬁeld of view TTL loupes (Designs for Vision).|
There is always a price to be paid for the increased amount of visual information that is provided by higher levels of magniﬁcation. Although the amount of visual information continues to increase, the value of the clinical information provided is maximized at around 20x magniﬁcation. The depth of ﬁeld, clinically, and the difﬁculty of the ﬁnite motor movements necessary to work at 20x make this power the approximate upper level of clinically valuable magniﬁcation. Stabilization of the gross motor joints (elbows and shoulders), through the use of a microsurgeon’s chair, allow for improved control of the micromotor muscles and joints (fingers and wrists). Tibetts and Shanelec34 showed, in working with high levels of magniﬁcation (20x power), that clinicians were able to learn how to shrink their movements from one to 2 mm (1,000 to 2,000 µm) increments to 10 to 20 µm (10 to 20/1,000th of a mm) movements at a time. Therefore, it is useful to appreciate that the limitation to precision of treatment is not in the hands…it is in the eyes.34
It is interesting to note that even though the magniﬁcation continuum for many clinicians may consist of 3 phases, some clinicians may never see the need to proceed past an entry-level set of loupes. However, others will jump from low power to a microscope, without using a medium level of magniﬁcation. On rare instances, a practitioner will actually not be able to become proﬁcient with low-power loupes, instead immediately jumping into a microscope. This can be because of the ergonomic value of the scope to sit upright, relieving back and neck pain; or due to the stereoscope vision that provides easier eye accommodation (for some clinicians) than that found with the convergent vision of loupes (Figure 6). The Magniﬁcation Continuum is simply a concept to describe the process that many clinicians progress through when they begin to grasp the value of the magniﬁcation for improving their work and if properly aligned for their ergonomic posture.
|Figure 8a. Microscope (Global Surgical) capable of providing 6 different magniﬁcations (2.1x, 3.2x, 5x, 8x, 13x, and 19.2x). A simple one-chip medical-grade cube camera (black square on right) provides video so that patients can see in real time during exams and procedures.||Figure 8b. The G6 Operating Microscope (Global Surgical), with HD digital video camera on left and a digital single lens reflex camera on right side of microscope.|
|Figure 9a. Microscope-centered operatory.||Figure 9b. G6 Dental Operating Microscope and “microsurgeon’s” chair being used for restorative dentistry in the operatory.|
|Figure 10. The Magniﬁcation Continuum, showing the operator moving from the naked eye on the left to the operating microscope on the right. In this case, note the improved posture allowed with increasing levels of magniﬁcation; the longer working distance provides a more neutral and balanced posture.|
The author has progressed through entry-level loupes, 3.5x and 4.5x loupes (Figure 7), and, for the last 16 years, has completed almost 100% of any clinical work through the operating microscope (G6 Microscope [Global Surgical]) (Figures 8a to 9b). In the author’s current office, all 9 operatories have a microscope available for all procedures. Furthermore, all the operatories have been designed to function ideally with the microscope as the centerpiece visually, ergonomically, and functionally. The increasing ability to see with higher levels of magniﬁcation (Figure 10) has correlated with an ability to sit upright as the operator had the loupes adjusted properly (focal distance). In addition, as the clinician switched from ﬂip-up loupes to TTL loupes (TTL loupes have a higher declination angle), to an operating microscope, true neutral and balanced posture was achieved.
Magnification should be considered a must for all dental practitioners, regardless of age or visual acuity. The native resolution of the human eye limits our ability to visualize the details that are so crucial to delivering clinical excellence. Many dentists have moved beyond entry-level loupes to higher levels of magnification, and we are now seeing operating microscopes becoming more popular.
In the second part of this article series, we will explore the advantages of using telescopic loupes. It will conclude with the 4 advantages of using operating microscopes in the daily practice routine.
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Disclosure: Dr. van As has received honoraria from Global Operating Microscopes and equipment from Surgitel Loupes.