Week 5 Flashcards
How is surface roughness quantified?
by deviations in the direction of the normal vector of a real surface from it’s ideal form
If deviations are large, the surface is (smooth/rough). In contrast, if deviations are small, the surface is (smooth/rough).
rough
smooth
What is the relevance of roughness?
determines how a real object will interact with its environment
- rough surfaces = weaker
- irregularities = sites for failure
- may promote adhesion with water, microbes and cells
- may influence wettability
What are the roughness parameters?
most common
Rz = distance between highest peak and lowest peak
Ra = average roughness
What are three measures used to determine roughness?
- stylus profilometer
- needle that moves up and down and creates a graph - optical methods
- microscope with layers - AFM (nano-scale)
- similar to stylus but displacement of tip is measured by lasers
How do you modify roughness?
polishing
General processes by which a material’s structure and properties are probed and measured
biomaterials characterization
How are biomaterials characterized?
What are the four considerations for biomaterial characterization?
- length scales (hierarchy)
nano-, micro-, macro- scale - location dependence
which region? - surface only vs. bulk
- environmental effects
highly used to test bonding strength of dental materials
micro-tensile testing
What is micro-indentation?
What is nano-identation?
gained popularity after developing machines that can record small loads and displacements
Compare micro- and nano- indentation
What kind of tools are available?
uses visible light and a system of lenses to magnify images of small objects
light microscope
an optical microscope that uses fluorescence and phosphorescence instead of, or in addition to, reflection and absorption to study properties of organic and inorganic substances
fluorescence microscope
True or false: Fluorescent microscopes only use fluorescent samples in their natural forms.
False.
Samples can be in their natural form or treated with fluorescing molecules
allows us to identify cells and cellular components with a high degree of specificity
fluoresence micoscope
What are the three characteristics of fluorescence?
- identify components with specificity and monitor chemical/biological processes
- degradation of samples by high energy light sources
- improve resolution of an optical microscope
an optical imaging technique for increasing optical resolution and contrast of a microscope image by using a spatial pinhole placed at the confocal plane of the lens to eliminate out-of-foucs light
confocal microscope
What are the two benefits of confocal microscope?
- higher resolution
- 3D reconstruction or images
What are the 4 characteristics of a confocal microscope?
- high resolution images taken from focal plane
- 3D images by stacking 2D images
- slower than conventional microscope imaging
- expensive equipment
The ability of a biomaterial to perform its desired function with respect to a medical (dental) therapy, without eliciting any undesirable local or systemic effects in the recipient of that therapy, but generating the most appropriate beneficial cellular or tissue response in that specific situation, and optimizing the clinically relevant performance of that therapy
biocompatibility
The ability of a material to perform with an appropriate host response in a specific application
biocompatibility
Why is biocompatibility important to dentists?
What are the 5 biocompatibility requirements?
SHOULD NOT
1. sensitize and produce allergic reactions
2. undergo unwanted biodegredation
3. be carcinogenic
4. contain toxic diffusible substances which can enter the circulatory system
5. be harmful to soft and hard tissues
True or false: Biocompatibility is a property of how a material reacts with its local environment
True
What are three ways we can assess the biocompatibility of biomaterials?
- in-vitro tests
- direct tests
- indirect tests (with barriers) - animal tests
- usage tests
studies performed with microorganisms, cells, or biological molecules outside their normal biological context
in-vitro tests
What is an example of an in vitro test?
placing a material in contact with a cell, enzyme, or some isolated biological system
What is the ISO standard for biological evaluation of medical devices?
- Surface devices on the skin, mucosal membranes,
breached or compromised surfaces - External communicating devices with blood, tissue, bone, dentin
- Implantable devices
What is the ISO standard for dentistry - evaluation of biocompatibility of medical devices used in dentistry?
- Test methods for the evaluation of biological effects of medical devices used in dentistry.
- It includes testing of pharmacological agents
What are the two types of cells for in-vitro tests?
How do you measure cytotoxicity?
When using fluorescent microscopy to count cells, how can you tell which cells are alive and which are dead?
red = dead
green = alive
How is cell metabolism measured?
What are the 4 advantages of in-vitro tests?
- reasonable cost
- capital investments in facilities and equipment
- fast processing
- controllability
What is the main disadvantage of in-vitro tests?
cannot entirely predict overall biocompatibility of material
Describe in vivo tests using animals
mammals
- mice, rats, hamsters, sheeps, guinea pigs
- allows for the complex interactions between the material and a functioning, complete biological system to occur
What are the 4 disadvantages of in vivo testing in animals?
- difficult to interpret and control
- expensive
- time consuming
- ethical concerns/oversight
True or false: More than 100 million mice and rats are killed in US laboratories every year.
True
During this test, material causes inflammation to mucous membrane
mucous membrane irritation test
During this test, materials are injected intra-dermally to test for the development of skin hypersensitivity reactions
skin sensitization test
During this test, materials that will contact subcutaneous tissue or bone are evaluated. This is also known as the calvarial model.
implantation test
What are the two advantages of in-vivo tests?
- allows complex systematic reactions
- response more comprehensive than in-vitro tests
What are 4 disadvantages of in vivo tests?
- questionable final in-vivo usage
- expensive
- time consuming
- difficult to control
What are usage tests?
- animals or humans (clinical trial)
- biomaterial placed identical to the clinical use
- gold standard
In dentistry, the 3 main targets for usage tests are
- dental pulp
- periodotium
- gingival tissue
What are the 2 advantages of usage tests?
- high fidelity
- real simulation of situation
What are the 5 disadvantages of usage tests?
- very expensive
- very time consuming
- major legal/ethical issues
- difficult to control
- difficult to interpret and quantify
