The development and applications of replica techniques for use with scanning electron microscopy
Pameijer, Cornelis H.
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With the introduction of the scanning electron microscope the knowledge on surface characteristics of the microtopography has increased tremendously. The unique features such as the great depth of field, the outstanding contrast and the three dimensional image make ·it possible to explore microstructures which were unknown. Stimulated by the successes of the practical applications in metallurgy, researchers in biology and medicine explored the possibilities of applications in their fields. Although specimen preparation involves less work than required for transmission electron microscopy it would be an understatement to assume that it is trouble free. All biological tissue shrinks when exposed to a high vacuum. This vacuum is one of the requirements during specimen preparation when a metal is evaporated to form a conductive layer on the specimen. Accelerated electrons interacting with the surface of the specimen will be conducted by this metal layer and by means of amplification of the signal produce an image on a cathode ray tube. It is the creation of specimen preparation artefacts which may lead to misinterpretation. Some artefacts induced by the vacuum are obvious as to their arteficial nature; others are subtle changes which may not be recognized as such. In order to determine as to whether artefacts are created during specimen preparation, replica techniques were developed which duplicate the specimens prior to exposure to the high vacuum of the metal evaporator. The original and positive replica were then prepared simultaneously for scanning electron microscope observation. A comparison between originals and replica specimens revealed that 1n observing biological tissues the introduction of artefacts is inevitable. Some artefacts were easily recognizable as such, others could very well be interpreted as being normal and in these cases the replicas provided in a decisive answer. A variety of controversial subjects in dentistry were investigated and the specimens replicated in either applying a hard or a soft replica technique. When hard biological tissues were investigated the hard replica technique was utilized; when no pressure on soft tissues was allowed a pressureless soft replica technique was applied. It can be concluded that the two techniques have a definite application in dental research with further possibilities in other sciences. The feasibility for longitudinal studies is a valuable asset to existing experimental design.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact firstname.lastname@example.org.Thesis (D.Sc.D.)--Boston University, School of Graduate Dentistry, 1973.Includes bibliography (leaves 199-209)
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