Structure and properties dental materials 2

Hydrogen bonding is a special case of dipole attraction in highly polar compounds.

Covalent bonding involves the sharing of two valence electrons between adjacent atoms, forming an electrically neutral molecule, such as dental resins.

A smaller indentation indicates a higher hardness number, meaning the material is harder.

Change in length per unit of original length of a material when its temperature is raised by 1 degree.

Thermal conductivity governs heat transfer through materials, with high thermal conductivity materials acting as conductors and low thermal conductivity materials acting as insulators.

Key chemical properties include solubility, toxicity, reactivity, and biodegradation.

Ionic bonding involves the transfer of an electron from one atom to another, forming a stable compound, as seen in gypsum structures and phosphate-based cements.

As the length of the prosthesis increases, the deflection increases.

The elastic limit is the maximum stress a material can withstand before it becomes plastically deformed.

Fracture toughness

How long a restoration lasts and its performance over time.

The more rigid the alloy, the thinner sections can be used without risk of bending.

A process that gives strength and adaptation to amalgams by condensing them for better fit to the walls.

Allotropy, which involves different structural modifications of an element (e.g., diamond and graphite), and polymorphism, which refers to changes in morphology.

Amount of heat needed to raise the temperature of one gram of material by 1 °C.

Compressive stress

Many methods depend on the penetration of a small symmetrically shaped indentor into the surface of the material being tested.

Ductility is measured by % elongation, reduction in cross section, or via the cold bend test.

Dental amalgam has a compressive strength which is nearly six times higher than its tensile strength.

Strain is the relative deformation of an object subjected to stress, defined as the change in length per unit length.

The modulus of elasticity describes the relative stiffness or rigidity of a material, measured by the slope of the elastic region of the stress-strain graph.

Plastic deformation

It is important to prevent thermal mismatch, which can lead to marginal failure and leakage due to different rates of expansion and contraction.

Metals & alloys, polymers, ceramics, and composites.

Advantages include easy manipulation and rigidity due to polymerization; disadvantages include thermal stability issues and potential brittleness.

Some light is reflected, some is refracted, some is absorbed, and some is transmitted, making enamel translucent.

The dominant color of the object, represented by dominant wavelengths present in spectral distribution.

Strength

Amalgams are brittle, and cracks can destroy them.

Shear stress

Plastic deformation is irreversible or permanent; it cannot be recovered when the force is removed.

The amount of light an object can absorb or scatter.

Fatigue is progressive fracture under repeated loading or the stress at which a material fails under repeated loading.

It is important because dental materials are subjected to alternating forces during mastication or while in function.

The base under restoration should be rigid to increase the fracture resistance of the filling.

The range of loads that can be applied is from 1-3000 kg.

It refers to the lightness or darkness of a color, increasing towards the lighter end of the gray scale.

It requires a preload and may have indentations that disappear immediately upon removal of the load.

A phenomenon where viscosity decreases rapidly with increasing shear stress and recovers immediately upon decrease in shear stress.

Temperature-related properties include the coefficient of thermal expansion, thermal conductivity, and thermal diffusivity, which are important to prevent thermal shock and ensure compatibility with dental tissue.

The rigidity of major connectors in partial dentures controls the stability of the whole design.

To prevent crack propagation.

A mixture of different metals.

They must mimic the interaction of light with natural teeth for aesthetic purposes.

By applying an equation relating force to the area or depth of the indentation.

It is used to determine the hardness of dental metallic materials.

The change in the color of an object due to a change in the light source.

The resistance of a liquid to flow, controlled by internal frictional forces within the liquid.

Most materials have a softening temperature far above mouth temperature, which prevents them from creeping in dental applications.

The magnitude of the load and the number of cycles.

Amorphous SiO2 is glass, while crystalline SiO2 is quartz, characterized by a highly ordered arrangement of crystals.

It measures the quantity of heat in calories or joules per second passing through a body of 1cm thickness and 1cm² cross-sectional area when there is a temperature difference of 1 degree.

Hardness is a surface property that refers to the ability to resist scratching in mineralogy and the resistance to indentation or penetration in metallurgy.

Flexibility represents the ease by which the impression can be removed from the mouth.

Dental amalgams consist of three phases and are also considered an alloy.

To compensate for the free mercury that rises to the superficial layer and to ensure adequate adaptation.

Materials used to construct artificial organs, rehabilitation devices, or prostheses and replace natural body tissues; non-viable materials intended to interact with biological systems.

Primary bonds are strong chemical bonds with high melting points, while secondary bonds are weaker, involving dipole forces without electron sharing.

Deformation (∆L)

Thermal conductivity is significant for materials like denture bases and metallic fillings, as it affects how heat is transferred through these materials.

Yield strength is the average level of stress at which a material exhibits a certain degree of plastic deformation.

For brittle materials that exhibit only elastic deformation, stresses at or slightly above the maximal elastic stress result in fracture.

The two types of impact testers available are Charpy and Izod.

The approximate ratio of the diagonals is 7:1.

Many polymers such as waxes, rubber, and plastics can creep considerably at room temperatures.

Temperature cycling, pH fluctuation, saliva viscosity, mechanical forces, and polymerization shrinkages.

Thermal conductivity (K) divided by the product of specific heat (Cp) and density (P).

Maximum flexibility is defined as the strain which occurs when a material is stressed to its proportional limit.

A combination of two or more materials, where each material forms its own phase.

An irregular structure where atoms are in non-repeating units, commonly found in polymeric-based materials.

Impact strength is the total energy absorbed by the material before fracture when struck by a sudden load.

The study of deformation and flow characteristics of matter.

Dental materials should be non-toxic, non-irritant, should not have cariogenic or allergic potential, and must be harmless to pulp if used as filling material.

Tensile stress

The heat of fusion is the amount of heat in calories or joules required to convert 1g of material from solid to liquid at its melting temperature.

Pulp pain caused by electrical current produced when two dissimilar metals contact.

The indentor may be made of steel, tungsten carbide, or diamond and shaped as a sphere, cone, or pyramid.

Brittle materials demonstrate no or very little plastic deformation on application of load and are weak in tension.

It is not suitable for determining the hardness of brittle materials and tends to fracture them.

The proportional limit is the greatest stress that a material will sustain without deviation from the law of proportionality of stress to strain.

Wetting is the ability of a liquid to flow easily over a surface and adhere to it, which is crucial for adhesion to occur.

Analysis of the problem (diagnosis).

The study of composition, structure, and properties of biomaterials used in dentistry and how they interact with the environment.

Destructive environment due to temperature changes, pH fluctuations, saliva, and mechanical forces.

Elastic deformation

It produces a symmetrically shaped indentation that can be measured for depth, area, or width.

The clinical stress of brittle materials is reduced when large flaws are present or if stress concentration areas exist due to improper design.

The degree of saturation of a particular hue.

It is not suitable for materials with elastic recovery.

The contact angle is a measure of wettability; complete wetting occurs at a contact angle of 0 degrees, while no wetting occurs at 180 degrees.

Material changes temperature very fast, leading to quicker heat transfer and potential damage.

Most ceramics fracture before any plastic deformation can occur.

An electrochemical process where a solid, usually metal, is attacked by an environmental agent, leading to partial or complete dissolution.

Isomerism refers to the ability to change the arrangement of atoms/molecules by altering surrounding physical conditions, including allotropy and polymorphism.

Ceramics have a regular arrangement of crystals, while glass has an irregular arrangement of crystals.

Hue, value, and chroma.

They do not have a definite melting temperature and gradually soften with increased temperature.

Elastic strain is reversible, while plastic strain represents a permanent deformation.

A property where a material does not flow until sufficient energy is applied to overcome its yield stress.

Metallic bonding features free valence electrons that create an electron cloud, allowing for high thermal and electrical conductivity, as seen in amalgam.

It is a rapid method for hardness determination and is good for testing viscoelastic materials.

It can be used in materials with varying hardness and allows comparison of the hardness of tooth enamel to other substances.

Static creep is the time-dependent plastic strain of a material in response to a constant or static load that produces stresses below the proportional limit.

Van der Waals forces are weak interatomic forces resulting from unequal sharing of electrons in polar molecules and fluctuating dipoles in non-polar molecules.

It is an important criterion for selecting dental materials.

The success of the material may depend on manipulation and handling when in liquid state, as many materials are mixed as fluid pastes that solidify.

Burnishing of a cast metal margin is a process used to reduce the width gap between the crown margin and the tooth surface.

The appearance of a material on a radiograph, important for detecting secondary caries under restorations.

If the liquid does not wet the surface, adhesion between the liquid and the adherend will be negligible or non-existent.

It is suitable for brittle materials and specifically useful for hardness testing of small areas and very hard materials.

Cements and impression materials.

Absorption, which is the uptake of liquid by solid, and adsorption, which is the concentration of molecules at the surface of a solid or liquid.

Dynamic creep refers to the creep of a material when the load, below the proportional limit, is applied in a cyclic manner.

Creep can cause deformation of restorations and lead to an unacceptable fit of dental prostheses.