Date post: | 11-Apr-2017 |
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Topographic analysis and physical testing of dental materials
By Mohamed Mahmoud Abdul-Monem
Assistant lecturer Dental Biomaterials Department
Faculty of dentistryAlexandria University
Egypt
Topographic analysis of materials
• Surface topography is the local deviations of a surface from a perfectly flat plane.
• The topography of a surface is known to substantially affect the bulk properties of a material.
• Surface topography may be measured in two ways:
1. Contact methods: Involve dragging a measurement stylus (profilometer) across the surface.
2. Non-contact methods :1. Confocal microscopy2. Focus variation3. Structured light4. Electron microscopy5. Photogrammetry
Topographic analysis
• Profilometer• Stereo microscope• Scanning electron microscope (SEM)• Environmental SEM• Scanning transmission electron microscope• Atomic force microscopy• Confcal microscopy• Fluorescence microscopy
Profilometer
Stereo microscope• A low powered
microscope which provides a stereoscopic view of the sample, commonly used for dissection.
• Typically using light reflected from the surface of an object rather than transmitted through it.
SEM
• A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons.
• The electrons interact with atoms in the sample, producing various signals that contain information about the sample's surface topography and composition.
Environmental SEM• Samples are observed in low-
pressure gaseous environments and high relative humidity (up to 100%)
• ESEM is especially useful for non-metallic and biological materials because coating with carbon or gold is unnecessary.
• Uncoated Plastics and Elastomers can be routinely examined, as can uncoated biological samples.
Scanning transmission electron microscope (STEM)
• The SEM can also be used in transmission mode by simply incorporating an appropriate detector below a thin specimen section .
Atomic Force Microscope(scanning force microscope)
• Is a very-high-resolution type of scanning probe microscopy(SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit.
• The information is gathered by "feeling" or "touching" the surface with a mechanical probe.
• Compared to competitive technologies such as optical microscopy and electron microscopy, the major difference between these and the atomic-force microscope is that the latter does not use lenses or beam irradiation.
• Applications in the field of solid state physics include:(a) the identification of atoms at a surface, (b) the evaluation of interactions between a specific atom and
its neighboring atoms, and (c) the study of changes in physical properties arising from
changes in an atomic arrangement through atomic manipulation.
Confocal laser scanning microscope
• Confocal : denoting or using a microscope whose imaging system only collects light from a small spot on the specimen, giving greater resolution.
• An optical imaging technique for increasing optical resolution and contrast of a micrograph by means of adding a spatial pinhole placed at the confocal plane of the lens to eliminate out-of-focus light.
• It enables the reconstruction of three-dimensional structures from the obtained images by collecting sets of images at different depths (a process known as optical sectioning) within a thick object.
• The Confocal Laser Scanning Microscope (CLSM) is an optical microscope that includes a laser light as a light source and an electronic system which helps on image processing.
• It obtains high-resolution and extremely thin optical image sections, removing the interference caused by the light arriving from the different optical fields across the thickness of the sample, and focusing on a single plane (confocal).
Fluorescence microscopy
• Optical microscope that uses fluorescence in addition to, reflection and absorption to study properties of organic or inorganic substances.
• The specimen is illuminated with light of a specific wavelength (or wavelengths) which is absorbed by the fluorophores, causing them to emit light of longer wavelengths (i.e., of a different color than the absorbed light).
• Biological fluorescent stains• Immunofluorescent stains• Fluorescent proteins
Physical testing of materials
Physical testing of materials
• Rheometer• Colorimeter • XRD• Differential scanning calorimeter• Pycnometry• Particle size analyzer• Mercury dilatometer• Optical tensiometer
Rheometer
• is a laboratory device used to measure the way in which a liquid, suspension or slurry flows in response to applied forces.
colorimeter
XRD
• is a measuring instrument for analyzing the structure of a material from the scattering pattern produced when a beam of radiation or particles (such as X-rays or neutrons) interacts with it.
Differential scanning calorimeter
• Differential scanning calorimetry (DSC) is a tool to determine a series of temperature transitions in materials, such as the Tg and melting temperature.
Pycnometry • Pycnometry is a technique
used to determine material densities.
• It is also possible to calculate volumetric shrinkage in polymerizations, by equating the densities of the material in the monomeric and polymeric states.
Particle size analyzer
• Particle size analysis, is the technical procedure which determines the size range, and/or the mean size of the particles in a powder or liquid sample.
Mercury dilatometer
• The mercury dilatometer method uses the variation in height of a mercury column caused by composite shrinkage to calculate total volumetric shrinkage.
Optical tensiometer• Optical tensiometers are used in
research, quality control and process control to study:
• wettability ·• spreading · • absorption · • adsorption · • cleanliness · • surface tension ·• interfacial tension ·• contact angles ·• surface heterogeneity · • interfacial rheology ·• surface free energy
Porosimetry• Porosimetry is an analytical technique used to determine
various quantifiable aspects of a material's porous nature, such as pore diameter and total pore volume
• The technique involves the intrusion of a non-wetting liquid (often mercury) at high pressure into a material through the use of a porosimeter.
• The pore size can be determined based on the external pressure needed to force the liquid into a pore against the opposing force of the liquid's surface tension.
References
1. Philips’ science of dental materials.12th edition2. Craig’s restorative dental materials.13th edition3. H Assender et al.How Surface Topography Relates to
Materials' Properties.Science Mag .2002;2974. https://en.wikipedia.org/wiki/Scanning_electron_mic
roscope5. M Vilotic et al.Atomic force microscopy in metal
forming and dental materials characterization.Journal for technology of plasticity .2012;37:173-186
6. https://en.wikipedia.org/wiki/Confocal_microscopy
Thank You