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- This topic has 3 replies, 3 voices, and was last updated 26/03/2012 at 4:55 pm by Dr Chetna Bogar. This post has been viewed 219 times
03/10/2011 at 1:00 pm #9991
A microscope is an important instrument used in histopathology laboratory to observe the tissues. The magnification it provides enables us to see the structures otherwise invisible to the naked eye.
Types of microscopes
Microscopes are broadly classified as simple microscopes and compound microscopes.
1) Simple microscope
It has a single lens system through which the upturned image of the object is seen.
2) Compound microscopes
These are again classified into 2 types
• Light microscope
• Electron microscope
They are of the following types
i)Bright field microscope
ii)Dark field microscope
iii)Phase contrast microscope
They are of 2 types
i)Transmission electron microscope(TEM)
ii)Scanning electron microscope(SEM)
03/10/2011 at 6:00 pm #14600
It is universally recognised that what often influences the quality of treatment is the level to which the clinician can see.
The dental microscope is unparalleled in its ability to provide an intensely illuminated, magnified image of the operating site. Despite the fact that Surgical Operating Microscopes [SOM] have been used by medical specialties since the sixties; the SOM has not been so readily accepted into dentistry.
Whilst general dental practitioners have predominantly seen dental microscopes as specialist equipment, typically endodontists have recognised and readily acknowledged the benefits of operating at higher magnification with powerful illumination. More recently however, it is becoming an increasingly held belief that the dental microscope offers considerable advantages over direct visualisation and loupe magnification.
Improved Magnification and Lighting
The higher magnifications achieved with a dental microscope improves the end result by not only enlarging the operating site, but also by providing intense homogenous co-axial lighting. Both these factors allow the clinician to visualise features not otherwise perceptible to the naked eye or even with loupes. Such improved visual acuity improves precision and the range of treatment options available. Microscopic examination methods and microsurgical techniques have transformed the way that the modern clinician operates.
Improved ergonomics and reduced musculoskeletal strain.
Other than the obvious advantage of higher magnification, the microscope offers distinct ergonomic advantages over loupes and the naked eye. Dentists work in conditions that frequently produce musculoskeletal disorders. Physical load, repetitiveness and poor body posture when seeking visual approaches to poorly illuminated areas of the mouth all contribute towards the high risk of developing shoulder, neck and back complaints. The more upright posture of the clinician when using a dental microscope may contribute to less neck and back strain.
Improved Patient Communication and Acceptance of Treatment
One of the great benefits of capturing digital images is improving the patient’s dental awareness and their recognition for the necessity of a particular treatment. In the absence of symptoms, the majority of patients are unaware of the conditions of their mouths. Communication between the clinician and patient is improved infinitely by the clinician being able to demonstrate to the patient the condition of their teeth before, during and after treatment.
With a digital video or stills camera attached via a beam splitter to a surgical microscope, patients are clearly able to observe the enlarged image of their teeth. Cracks, failing restorations, defective crown margins and periodontal pathologies can all be easily identified by the clinician and shown to the patient as a high quality digital image. What is more, the patient can clearly see the improvement in the quality of care they have received by the use of a microscope.
Disadvantages of Dental Microscopes?
Some dental practitioners have concerns that the use of the microscope may unjustifiably slow down treatment; and feel that patient and staff resistance to this new technology may prove to be an insurmountable problem. Whilst it is true that the learning experience for the whole dental team is steep; a new approach to treatment fully integrating the microscope will gradually reduce the longer appointment times initially required.
Support staff will require time to learn the new methods of working, with fourhanded dentistry offering a considerable advantage. Besides, time wasted attempting to locate root canals, or refining crown or cavity margins, will be significantly reduced when compared to using loupes or the naked eye.
“There is no question that the introduction of the microscope into the delivery of dental care is profoundly significant…”
26/03/2012 at 4:55 pm #15333
The stereo or dissecting microscope is an optical microscope variant designed for low magnification observation or a sample using incident light illumination rather than transillumination. It uses two separate optical paths with two objectives and two eyepieces to provide slightly different viewing angles to the left and right eyes. In this way it produces a three-dimensional visualization of the sample being examined. Stereomicroscopy overlaps macrophotography for recording and examining solid samples with complex surface topography, where a three-dimensional view is essential for analysing the detail.
The stereo microscope is often used to study the surfaces of solid specimens or to carry out close work such as dissection, microsurgery, watch-making, circuit board manufacture or inspection, and fracture surfaces as in fractography and forensic engineering. They are thus widely used in large numbers in manufacturing industry, both for manufacture, inspection and quality control. It tends to make them of lower cost compared with conventional microscopes.
The stereo microscope should not be confused with a compound microscope equipped with double eyepieces and a binoviewer. In such a microscope both eyes see the same image, but the binocular eyepieces provide greater viewing comfort. However, the image in such a microscope is no different from that obtained with a single monocular eyepiece.Unlike a compound light microscope, illumination in a stereo microscope most often uses reflected illumination rather than transmitted (diascopic) illumination, that is, light reflected from the surface of an object rather than light transmitted through an object. Use of reflected light from the object allows examination of specimens that would be too thick or otherwise opaque for compound microscopy. Some stereo microscopes are also capable of transmitted light illumination as well, typically by having a bulb or mirror beneath a transparent stage underneath the object, though unlike a compound microscope, transmitted illumination is not focused through a condenser in most systems. Stereoscopes with specially-equipped illuminators can be used for dark field microscopy, using either reflected or transmitted light.
Scientist using a stereo microscope outfitted with a digital imaging pick-up and fibre-optic illumination
Great working distance and depth of field here are important qualities for this type of microscope. Both qualities are inversely correlated with resolution: the higher the resolution (i.e. the shorter the distance at which two adjacent points can be distinguished as separate), the smaller the depth of field and working distance. A stereo microscope has a useful magnification up to 100×, comparable to a 10× objective and 10× eyepiece in a normal compound microscope, and is often much lower. This is around one tenth the useful resolution of a normal compound optical microscope.
The large working distance at low magnification is useful in examining large solid objects such as fracture surfaces, especially using fibre-optic illumination. Such samples can also be manipulated easily so as to determine the points of interest. There are severe limitations on sample size in scanning electron microscopy, as well as ease of manipulation in the specimen chamber.Magnification
There are two major types of magnification systems in stereo microscopes. One is fixed magnification in which primary magnification is achieved by a paired set of objective lenses with a set degree of magnification. The other is zoom or pancratic magnification, which are capable of a continuously variable degree of magnification across a set range. Zoom systems can achieve further magnification through the use of auxiliary objectives that increase total magnification by a set factor. Also, total magnification in both fixed and zoom systems can be varied by changing eyepieces.
Intermediate between fixed magnification and zoom magnification systems is a system attributed to Galileo as the "Galilean optical system" ; here an arrangement of fixed-focus convex lenses is used to provide a fixed magnification, but with the crucial distinction that the same optical components in the same spacing will, if physically inverted, result in a different, though still fixed, magnification. This allows one set of lenses to provide two different magnifications ; two sets of lenses to provide four magnifications on one turret ; three sets of lenses provide six magnifications and will still fit into one turret. Practical experience shows that such Galilean optics systems are as useful as a considerably more expensive zoom system, with the advantage of knowing the magnification in use as a set value without having to read analogue scales. (In remote locations, the robustness of the systems is also a non-trivial advantage.)
Small specimens necessarily require intense illumination, especially at high magnifictions and this is usually provided by a fibre-optic light source. It utilises halogen lamps which provide high light output for a given power input. They are small enough to be fitted easily near the microscope, although often need cooling to ameliorate high temperatures from the bulb. The fibre-optic stalk gives the operator a high degree of freedom in choosing appropriate lighting conditions for the sample. The stalk is encased in a sheath which is easy to move and manipulate to any desired position. It is normally unobtrusive when the lit end is near the specimen, so usually does not interfere with the image in the microscope. Examination of fracture surfaces frequently need oblique lighting so as to highlight surface features during fractography, and fibre-optic lights are ideal for this purpose. Several such light stalks can be used for the same specimen, so increasing the illumination yet further.
Digital display with stereo microscopes
Recently various video dual CCD camera pickups have been fitted to stereo microscopes, allowing the images to be displayed on a high resolution LCD monitor. Software converts the two images to an integrated anaglyph 3D image, for viewing with plastic red/cyan glasses, or to the cross converged process for clear glasses and somewhat better color accuracy. The results are viewable by a group wearing the glasses. More usually a camera attached to one of the eyepieces will record conventional images.
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