03 May Microscopía
El uso de la magnificación en odontología se ha convertido en una herramienta de rutina para nosotros. La precisión de la tecnología utilizada es tal, que el ojo humano no es suficiente para conseguir unos resultados óptimos. Cinco ó incluso veinte aumentos son necesarios para realizar muchas de las preparaciones y diagnósticos que realizamos día a día. Adjuntamos un artículo de interés general sobre el tema:
You may remember the first time you saw a dentist wearing magnifying loupes; you probably thought the person must have a severe vision defect. That certainly was my opinion as I observed an elderly dentist wearing single-lens loupes and leaning almost into a patient’s mouth to accomplish an oral treatment pro- cedure. I had that naïve opinion for the first few years of my dental career, since magnifica- tion was not a popular aid to dental practice until later.
Although I was blessed with nearly perfect vision until approximately 55 years of age, I always felt the need to see more clearly some of the aspects of dental practice. After a few years of watching excellent den- tists routinely using magnifica- tion, I finally became inquisitive enough to try the concept myself. I found the extra appendage to my head to be objectionable and in the way. The lenses of the loupes soon became dirty and scratched. My posture degenerated as I leaned
in too close to the patients. The loupes were uncomfortable to wear on my nose. They were an infection control challenge. How- ever, after a few days of forcing myself to use loupes, I was con- vinced that my restorative treat- ment was being accomplished at a higher level of quality because of the magnification. My labora- tory technician asked me if I had started to use a new tech- nique, because the tooth prepa- rations were better. I became a routine user of magnification, but then many questions came into my mind.
This article poses some of those questions about magnifi- cation and answers them from scientific information, personal experiences and my work with many dentists in study clubs and hands-on clinical courses.
DOES USE OF MAGNIFICATION WEAKEN YOUR EYES?
After consulting with an ophthalmologist about magnification (oral communication, L. Noble, M.D., Sept. 25, 2003), I was informed that he and his colleagues agree that use of magnifying loupes does not harm or weaken the eyes, nor does it cause the user to become compromised in any way. How- ever, after wearing loupes for a period, the user becomes accus- tomed to seeing more detail than that apparent with natural vision, and a psychological feeling develops that something is being missed if depending solely on natural vision. This is an uncomfortable feeling if the magnification is not available. Furthermore, after several hours, the eyes require time to readjust to normal vision, just as they do each morning after the eye muscles have been dor- mant all night. Apparently, while using magnification, the eye muscles become accustomed to contracting to a given level, and they must relax again to regain normal function. To avoid or reduce this challenge, it has been suggested that those people wearing magnifying loupes should consider not wearing them all of the time; instead, they should use loupes for some procedures and unmag-
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Minified, normal vision for other procedures.
HOW CAN I OBTAIN MAGNIFIED IMAGES?
The closer you get to an object, the larger it appears to your eye. However, the closer you get to an object, the more difficult it is to focus, especially for older eyes. Single-lens loupes help you get closer to an object and focus your eyes on it. So-called ×5 single-lens loupes can create about ×2 magnification with normal eyes (oral communica- tion, J. Chang, Ph.D., Sept. 25, 2003). However, getting closer to the object can create poor pos- ture with the associated back, neck and shoulder pain. If you use surgical loupes or operating microscopes, the image appears larger because it has been opti- cally magnified, and the clini- cian can sit at a comfortable dis- tance from the operating site.
WHAT MAGNIFICATION LEVEL SHOULD I USE?
The answer to this question is personal. The taller the practi- tioner is, generally the higher the magnification should be, since the practitioner’s head is farther from the operating site and the image is smaller. Con- sultants advise that if a person is 5 to 51⁄2 feet tall, the magnifi- cation needed (on average, about ×2.5) is less than that needed if the person is 61⁄2 feet tall and therefore naturally sitting far- ther from the operating site (on average, about ×3 or more) (oral communication, J. Chang, Ph.D., Sept. 25, 2003). For any specific clinician, the higher the magnification, the greater detail that can be observed, and the smaller the viewing field. Addi- tionally, some practitioners prefer lower magnification, while others cannot work well without higher magnification. The most popular magnification level is about ×2.5 for an average-sized person. As an average-sized man, I have con- cluded the following on the basis of my clinical experience.
For procedures such as greeting a patient, reading patient records, making alginate impressions, most of the com- plete denture procedures, rou- tine tooth extraction and similar procedures, I prefer to use normal corrected but unmagni- fied vision. In other words, my regular glasses. If magnification or vision correction is not being
coectomies or other procedures that are very small in scope). dHigher magnification using clinical microscopes has had a positive influence in endodon- tics. For procedures that have a limited operating field (such as endodontic therapy, finishing single-crown preparations or single-tooth operative dentistry), use of a clinical microscope at magnification levels up to ×20 has been shown to be a signifi- cant aid to quality treatment. However, learning to use the microscope requires time and effort, and the cost of the devices is significant.
WILL USE OF LOUPES INFLUENCE MY POSTURE WHILE OPERATING?
The focal distance between the operator’s eyes and the oper- ating site is a critical distance that influences posture signifi- cantly. Therefore, the focal length of the loupes should be matched to your preferred oper- ating distance. If you select loupes with a focal length that is too short or too long, you will be uncomfortable while operating, and muscle pain eventually will result. The so-called declination angle depends on many of your physical characteristics. If the declination angle forces you to sit with your head tilted, pain will result. Alignment of binocular loupe optics is critical also. Eyestrain results if they are not aligned properly.
While wearing loupes, clini- cians should be able to sit or stand in a comfortable position with normal posture. This requires proper selection of focal length and declination angle, as well as proper alignment of the binocular loupe optics.2 Selection of loupes with any of the three factors not related to the phys-
For procedures that have a limited operating field, use of a clinical microscope at magnification levels up to x20 has been shown to be a significant aid to quality treatment.
used, protective safety glasses should be in place during all oral procedures.
dFor procedures such as tooth preparations on typical, normal- sized teeth, routine surgical pro- cedures on soft tissue or bone, seating crowns or evaluating dental hygiene patients, I prefer magnification at about ×2.5.
I prefer ×4 or higher magnification for procedures to be accomplished on very small teeth, or for procedures that are extremely delicate and require precision hand movements (such as crown preparations or crown seating on lower anterior teeth, evaluating if a fixed prosthesis is loose, evaluating the fit of a long-span fixed prosthesis, api-
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Copyright ©2003 American Dental Association. All rights reserved.
ical characteristics of the wearer can cause poor posture and
the resultant shoulder, neck
and back pain and physical debilitation.
WHAT ARE THE LIMITATIONS TO HIGHER- POWER MAGNIFICATION?
Many oral procedures require various objects to be parallel to one another or symmetrical with other objects. Examples are cre- ation of a multiabutment fixed prosthesis, placement of several implants or determination of the facial midline for denture setups. A wide field of vision is required for these procedures. In my opinion, for an average-sized clinician, use of magnification of more than about ×2.5 while accomplishing such procedures causes inadvertent errors because of the limited vision field, requires poor posture and slows the procedures signifi- cantly. Higher-power magnifica- tion often influences posture negatively if the focal length of the magnifiers does not allow the clinician to sit in a normal posture. Additionally, if the clin- ician requires vision correction or if safety glasses are being worn when loupes are not in use, there is a continual need to exchange loupes with normal glasses.
SCRATCHING MAGNIFYING LENSES
Dental procedures produce sig- nificant debris, much of which contains very hard particles of tooth structure or metal. Although most magnifying loupes have protective coatings on the lenses, unless extreme care is taken, some lenses soon become scratched, cloudy and difficult to use. When cleaning lenses, the clinician should remove gross debris carefully, using a water lavage if the loupes are water-resistant, fol- lowed by use of microscope- cleaning wipes or lens-cleaning cloths provided by some loupe manufacturers. I recommend purchasing loupes with water- resistant lenses to allow proper cleaning and disinfection. If the loupes are not water-resistant, a moist Kimwipes (Kimberly- Clark, Neenah, Wis.) tissue used with the same manufacturer’s lens cleaning solution should be blotted on the lens to remove the major debris, followed by use of alcohol solution is recom- mended. If the lenses are water- resistant, products such as Lysol Disinfectant Spray (Reckitt Benckiser Professional, Wayne, N.J.) may be sprayed into a gauze sponge and used to wipe the frames and lenses. When- ever possible, the clean, disin- fected loupes should be in posi- tion on the clinician when the clinical procedure is started and left in place until the clinical procedure is completed, and hand contact with the loupes should be avoided during the procedure. At the completion of the clinical procedure, the lenses can be cleaned and the frames and lenses disinfected.
WHAT ARE THE POPULAR BRANDS OF LOUPES?
According to estimates I have gathered from several loupe manufacturers and informal polls I have conducted in my continuing education courses, the most popular high-quality loupes in North America are manufactured by Designs for Vision (Ronkonkoma, N.Y.); Orascoptic/SDS (Middleton, Wis.) and General Scientific/ SurgiTel (Ann Arbor, Mich.).
There are numerous other brands that also are of high quality but are not as well- known as the brands described above: Carl Zeiss (Chester, Va.); Den-Mat (Santa Maria, Calif.); Eagle Optical Products (Bow- mansville, N.Y.); Keeler Instru- ments (Broomall, Pa.); and SheerVision (Rolling Hills Estates, Calif.).
Practitioners interested in loupes should request informa- tion from the respective com- panies in which they have interest, then make the decision regarding which brand seems most acceptable to them. The
Ideally, all areas of the loupe should be disinfected with a high-level disinfectant after each patient.
successive new microscope cleaning wipes to eventually clean the lens, and concluding with disinfection. In some pro- cedures, such as multiple tooth preparations, cleaning the magnifying lenses may be required more than once during the procedure.
Magnifying loupes collect debris from many procedures during a clinical day. Infection control is difficult at best. Ideally, all areas of the loupe should be dis- infected with a high-level disin- fectant after each patient. How- ever, facing the reality that most dentists using loupes have only one set of loupes, and that some loupes will not tolerate constant use of disinfectants, the infec- tion control challenge is obvious.
Disinfecting with high ethyl
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most popular brands have many advocates and offer different alternatives that need your con- sideration. Some of the lesser- known brands cost less.
Some practitioners prefer to use another category of very low-cost single-lens loupes for the procedures that produce the most debris, such as air abra- sion, cutting metal out of teeth and polishing procedures. An example of a company selling low-cost loupes is Almore International (Portland, Ore.). Of course, many of the advan- tages available in more expen- sive loupes are not present in the low-cost versions, and pos- ture will be compromised, but on the other hand, destruction of the loupes by accumulation of debris and scratches is not a major financial loss. Some prac- titioners use high-quality loupes for most procedures and inexpensive loupes when they know the oral debris will be significant.
The treatment of oral disease using a microscope needs fur- ther observation and use by practitioners. There is a good potential for producing higher- quality treatment in some areas of dentistry when a clinical microscope is used. A well- established clinical microscope company is Global Surgical Corporation (St. Louis).