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