Biomaterials 1 Flashcards
There is a challenge for end users to critically evaluate the claims made on the reported _________ and to relate these claims carefully to well- established physical properties for the specific classes of materials.
performance of dental materials
The dentist needs to understand the fundamental principles of dental materials to be able to properly and critically evaluate ________.
Advances in dental materials
Dentists need to be able to critically evaluate ________, and a large body of dental literature is related to dental materials.
scientific literature
Materials used in the construction of a dental prosthesis but that do not become a part of the structure. These include acid-etching solutions, impression materials, casting investments, gypsum cast and model materials, dental waxes, acrylic resins for impression and bleaching trays, acrylic resins for mouth guards and occlusion aids, and finishing and polishing abrasives.
Auxiliary Dental Materials
Metallic, ceramic, metal-ceramic, or resin-based materials used to replace, repair, or rebuild teeth and/or to enhance esthetics. The ideal restorative material would be biocompatible, bond permanently to tooth structure or bone, match the natural appearance of tooth structure and other visible tissues, exhibit properties similar to those of tooth enamel, dentin, and other tissues, and/or be capable of initiating tissue repair or the generation of missing or damaged tissues.
Restorative Materials
Cements, metals or resin-based composites that are placed and formed intraorally to restore teeth and/or to enhance esthetics. A composite is when a monomer resin contains inorganic or polymeric filler particles that are bonded to the matrix resin by means of an organosilane coupling agent.
Direct Restorative Materials
Ceramics, metals, metal-ceramics, or resin-based composites used extraorally to produce prostheses that replace missing teeth, restore damaged teeth, and/or enhance esthetics.
Indirect Restorative Materials
Cement- or resin-based composites used for a period of a few days to several months to restore or replace missing teeth or tooth structure until a more long-lasting prosthesis or restoration can be placed.
Temporary Restorative Materials
Cements, coatings, or restorative materials that either seal pits and fissures or release therapeutic agents such as fluoride and/or other mineralizing ions to prevent or arrest the demineralization of tooth structure.
Preventive Dental Materials
Name the property: Esthetics is critical in dental restorative materials, especially with the increased use of bleaching and whitening technologies. Thus, the interaction of light with the restorative materials must mimic the interaction of light with the natural tooth, and the knowledge of the underlying scientific principles of color and other optical effects is essential.
Optical
Name the property: Materials differ markedly in their ability to conduct electric current. The current may be carried either by free electrons (in metals) or by ions in solution. This effect is pronounced in metals that are widely used in dentistry. Thus, electrical properties, especially the electrical conductivity or resistivity, are important to understand because the pulp is sensitive to microcurrents. Electrical properties are also important because the electrochemical properties of a material govern how corrosive a material may be in the oral environment.
Electrical and Electrochemical
Name which property includes
Reflection Refraction Absorbance Transmittance Translucence Opacity Color Fluorescence
Optical
Name which property includes Electrical Resistivity Electrode Potential Electromotive Series Corrosion
Nobility Passivation
Electrical and Electrochemical
______ plays a role in economic considerations. E.g., gold alloys are twice as dense as non-noble (base metal) alloys used for the same restorative purposes. Since the same volume of alloy is used to cast a restoration, the actual cost difference is not just the difference of the cost of alloys per unit weight. _____ also may play a role in function, e.g., the retention of upper dentures.
Density
Name the property: If a restorative placed in a deep cavity transmits too much heat to the dental pulp, it can cause thermal shock and trauma. If it thermally expands and contracts much more than the tooth it is placed in, marginal failure and leakage can result. Yet denture bases need to be able to transfer some heat to convey the sensations of heat and cold from food and beverages
Thermal
This is the ability of a material to conduct heat. Another way of saying it is how MUCH heat will flow through the material, and is defined as the rate of heat (cal/sec) passing through a material 1 cm thick with a cross section of 1 cm2 having a temperature difference of 1 K (or ̊C). In general, _______ increase in the following order: polymers < ceramics < metals.
Thermal Conductivity
With restorative materials, we are most concerned with responses to transient temperature changes (e.g., when a hot or cold food or beverage is ingested), and the material experiences a change in the environmental temperature. In these instances, the temperature is not constant but changes, depending on how well the heat is conducted and how much heat is absorbed by the material in raising the temperature of the material. This is where _______ plays a part. ________ is the measure of how quickly the material or tooth reaches equilibrium temperature. It takes into account how much energy the material itself needs to heat up. Here, Cp is the specific heat (the number of calories required to raise the temperature one degree) and ρ is the density in grams per cm3. Thus, a material with low specific heat and high thermal conductivity has high diffusivity (Δ) and temperature easily passes through the material. Gold has about one tenth the specific heat of dentin and about 500 times the thermal conductivity. A pure gold filling would thus protect the tooth pulp very poorly from a thermal transient compared to natural dentin.
Thermal Diffusivity
When materials undergo a temperature increase, the vibrational motion of atoms and the mean interatomic (bond) distances increase resulting in an increase in volume. The increase is described by the coefficient of ________. Here L is the original length, ΔL is the change in length and ΔT is the temperature change. This parameter is extremely important in applications as broad-ranging as producing cast restorations that fit, and maintaining the seal at a restoration margin.
thermal expansion
Thermal energy required to covert a liquid to a vapor
Heat of Vaporization
Thermal energy required to convert a solid to a liquid
Heat of Fusion
Name the property which includes Melting Point
Fusion Temperature
Solidus Temperature
Softening Point Eutectic Temperature Glass Transition Temperature Liquidus Temperature Specific Heat
Thermal
Unlike atoms in the interior of a material that are surrounded by other atoms that are equally attracted to each other, atoms on the surface are not surrounded by other atoms that are equally attracted to each other, leading to an increase in energy that is needed to form a surface. This energy is called the _______. These _______ per unit area are known as surface tension for liquids or surface free energy for solids. All systems attempt to minimize this energy. Liquids do so by assuming spherical shapes in the absence of other forces and minimizing the exposed surface area. Among solids, metals have high ________ while hydrocarbon polymers tend to have low ________.
surface energy
One way for a system to decrease surface energy is for a low surface tension liquid to wet and spread on a high surface energy solid. The net energy of the system is reduced by the elimination of the solid-air high-energy interface. ______ occurs most readily when the solid has a high surface free energy or when the liquid has a low surface tension.
Wetting
A third free energy, the interfacial energy between the solid and liquid, is also important in quantifying the degree of wetting, which is measured by the angle formed between a drop of liquid and a solid surface (Figure 1). This _______ decreases with improved wetting.
contact angle
Much of the _______ in dentistry depends directly on wetting. In fact, a general definition of an adhesive is a liquid that wets the substrate (adherend) of a different material well and then transforms to a solid. ______ is when this happens in two materials of the same species.
- adhesion
- cohesion
That action that produces or tends to produce motion in a body, or which changes motion in a moving body. Force is a vector quantity having both magnitude and direction.
Force
