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The Advanced Education in General Dentistry (AEGD) Clinic has taken the next step in state-of-the-art treatment through the integration of a dental operating microscope. A Leica M300 operating microscope was installed in the high tech dental suite of the AEGD in January.

The use of magnification in general dentistry has greatly increased over the past 15 years. It has become popular with many restorative dentists to aid their vision with head-mounted loupes, either on a headband, or more commonly mounted in or on prescription eyewear. Practitioners adept at using this type of magnification state that the increased image size facilitates better dentistry by reducing the amount of tactile clinical conceptualization needed, while increasing direct vision. Along with head-mounted magnification, some employ a focusable light source, mounted on or near the loupes. The addition of direct light is the key to obtaining optimal results with magnification. A magnified, but unlit image is reduced in contrast and color perception. The negative effect of poor light increases exponentially as magnification increases.

Although head-mounted magnification systems are a vast improvement over unaided vision in dentistry, they have some major shortcomings. These include limited magnification, no multi-user capability, limited depth of field, limited field of view, no co-observer capability, off-axis lighting, weight-related fatigue and less-than-optimal ergonomics. With the advent of the operating microscope, dentistry can overcome all of these problems.

Probably the most intriguing feature of the operating microscope is the range of magnification. With loupes, the operator is relegated to only one level of magnification. The operating microscope, with its superior optics, is capable of up to 5 different "stops" of magnification at the touch of a dial. As a practitioner becomes proficient with loupes, higher magnification is often desired for certain intricate procedures. Not only does increased loupe magnification entail an entire change in armamentarium, but also limits the operator once again if lower magnification is desired for more gross procedures. Nowhere in dentistry is this more the case, than in general dental practice. In addition, the range of magnification with operating microscopes is greatly increased. Whereas loupes offer single magnification usually between 2X and 6X, microscopes have multiple magnifications, generally between 2.5X and 16X (or even higher).

In addition to flexibility in magnification range, adjustments for multiple users are easy. The oculars on the microscope have calibrated dials for interpupillary distance and diopter settings, which can be memorized and easily entered when a different operator begins using the scope. Head-mounted loupes often require factory settings and are individualized to the user. Loupes are designed for individual use only; operating microscopes have built in flexibility for multi-user demands.

Depth of field and field of view are direct factors of the mechanical limitations of the optics. Due to size and weight considerations with head-mounted loupes, depth of field and field of view are impractical above a magnification of 6X. With ANY system, physics dictates that both depth of field and field of view are inversely proportional to magnification. But in comparing similar magnification of loupes and microscope, the operating microscope is far superior in both criteria. This fact makes higher magnification with the operating microscope practical, as well as enhancing "low power" capabilities.

One major difficulty in teaching students to use magnification is the lack of "real time" guidance while operating. The instructor must be able to see exactly what the student is viewing, in order to advise on adjustments to patient-instrument-hand-eye-head positioning to optimize the use of magnification. This is not possible with head-mounted systems. Often the student is left without adequate instruction on the use of magnification, which can lead to failure (the loupes sit in their case and collect dust). Operating microscopes can accomplish this needed co-observation by several means. As an image enters the scope, it can be split in two with a series of mirrors, called a beam-splitter. One image is then directed to the operator, while the other image is directed to a second set of oculars or a charge-coupled device (CCD) chip for viewing on a monitor. It is then easy for the instructor to evaluate and instruct the student without the need for switching positions. This translates into both increased quality of instruction, as well as operator efficiency.

The use of the CCD also introduces a simple way to perform sophisticated case documentation. The video output from the camera can be connected to a digital still camera, digital or analog video camera, or a computer workstation for non-linear video editing and still capture. Computer still capture also makes it possible to include digital intraoral images in a patient's electronic chart using many popular dental software packages. The advantage of this system verses a traditional intraoral camera or clinical SLR is that case documentation can be performed with little interruption of the procedure by simply activating a footswitch while working.

The lighting systems for head-mounted systems have some major drawbacks. The first and most obvious is the existence of a fiber-optic tether. In order to reduce weight, the actual light source is remote with a fiber-optic hose leading up to the operator's head. This means that the operator is forever tied to the counter, which can cause accidental damage to the fiber optics if the operator should get up and forget about the tether. The second impediment with this system is that the lighted image is always slightly at an angle to the magnified image, due to the fact that the light does not emanate from within the optics. This can (and does) cause unwanted shadows. The operating microscope has no shadows because its lighting system is mounted within its optics. Its intense light is directed on an exactly reciprocal path to the image and casts no shadow.

Ergonomics are also improved with the operating microscope. Most popular loupes are mounted in or on eyewear frames. This means that all of the weight of the magnification-lighting system is borne by the nose and ears. Even with the lightest of loupes, extended wear can cause fatigue to the facial skeleton and musculature. In addition, the fact that the magnification-lighting system is fixed directly to the operator's natural vision, any subtle movement of the head is transferred to the field of view. This can cause great neck, back, and shoulder strain, as well as adding procedural time for visual focus and re-focus. The operating microscope overcomes these problems by being self-supported via an articulating arm attached to a floor stand or wall/ceiling mount. The microscope "hovers" over the operating field and is not fixed to the operator, which reduces the negative effects of bodily movements and isometric muscular fatigue. Studies have shown that 87% of dentists suffer from some form of eyestrain, and another 60% live with chronic back pain. Head-mounted systems are a step in the right direction in improving operator ergonomics, but fall short. Loupes allow the practitioner to sit in a more upright position with an average working distance of 11 to 15 inches. Although this is an improvement to being "hunched over the patient," the operator must still direct his line of site directly over the operating field. This can cause the operator to lean over in an unsupported position. With the microscope, the image is directed through the objective lens to a prism, which redirects the image to an angled binocular. Furthermore, with the use of a co-observer monitor, it is possible for the advanced user to position the scope at severe angles for better observation and solely utilize the monitor for primary viewing. From a postural standpoint, this means that the operator does not have to lean over and can maintain a body frame-supported position.

Use of microscopes for general dentistry is gaining in popularity, both in the US and Europe. Manufacturers of these precision instruments in turn are becoming more and more responsive to the needs of the general dentist. There is little question that the employment of any form of magnification increases the quality and ease of dentistry. Operating microscopes represent the pinnacle of this technology. This year's AEGD residents have just completed "hands-on" training in utilization of the operating microscope and are beginning to integrate it into patient care. Temple Dental's AEGD is currently the only East coast, post-graduate, general dentistry training program to include the use of a dental operating microscope.