Lesson 2: Dental Materials - Physical and Chemical Properties of Solids

This set of vocabulary flashcards covers the physical, chemical, rheological, optical, thermal, and electrochemical properties of dental materials as presented in Lesson 2.

Physical Properties

Properties based on the laws of mechanics, acoustics, optics, thermodynamics, electricity, magnetism, radiation, atomic structure, and nuclear phenomena.

Chemical Properties

Properties based on the ways in which substances interact, combine, and change, as governed by their outer orbital electrons.

Rheology

The study of the deformation and flow characteristics of matter, whether liquid or solid.

Viscosity

The resistance of a fluid to flow.

Dilatant

Fluid behavior where resistance to flow increases as the rate of deformation (shear strain rate) increases.

Pseudoplastic

Viscous character in which the rate of flow decreases with increasing strain rate until it reaches a nearly constant value; also known as shear thinning.

Thixotropic

A property of gels and other fluids to become less viscous and flow when subjected to steady shear forces, returning to original viscosity when the force is removed.

Creep

The time-dependent plastic strain of a material under a static load or constant stress.

Flow

The term generally used in dentistry to describe the rheology of amorphous materials such as waxes.

Esthetics

The color and appearance of natural dentition.

Reflection

Electromagnetic radiation in the visible region interacts with an object through…

Hue

The dimension of color that refers to the color itself (e.g., Red, Yellow, Green).

Value

The dimension of color describing lightness or darkness.

Chroma

The dimension of color referring to saturation.

Metamerism

A phenomenon where objects that appear to be color matched under one type of light appear different under another type.

Daylight, incandescent, and fluorescent lamps

common sources of light in the dental operatory or laboratory, and each of these has a different spectral distribution

Shade Guide Group A

A group of shade tabs categorized by the hue of red-brown.

Shade Guide Group B

A group of shade tabs categorized by the hue of red-yellow.

Shade Guide Group C

A group of shade tabs categorized by the hue of gray.

Shade Guide Group D

A group of shade tabs categorized by the hue of red-gray.

Cones

Receptors in the human eye sensitive to red, blue, and green that send color signals to the brain.

Rods

Receptors in the eye that dominate at low light levels, causing color perception to be lost.

Bezold-Brücke effect

The effect where colors appear to change at highly intense brightness levels.

General Factors (extreme light, receptor fatigue, sex, age), The Dental Exception, Color Blindness

Factors Influencing Perception:

General factor of influencing perception

True color perception can be interfered with by extreme light levels, receptor fatigue, sex, age, memory, and cultural background.

The Dental Exception

Contrary to general factors, a 1995 study (Anusavice and Barrett) found that age, gender, and clinical experience do not affect the accuracy of dental shade matching.

Color Blindness

An optical deficiency occurring in approximately $8\%$ of men and $0.5\%$ of women, most commonly involving difficulty distinguishing red from green.

Thermal conductivity ($\kappa$)

The physical property that governs heat transfer through a material by conductive flow.

conductors

Materials that have a high thermal conductivity

insulators

materials of low thermal conductivity

Thermal diffusivity

A measure of the speed with which a temperature change will spread through an object when one surface is heated.

Coefficient of Thermal Expansion ($\alpha$)

The change in length per unit of the original length of a material when its temperature is raised $1\,^{\circ}\text{C}$ ($1\,K$).

Corrosion

An electrochemical process dependent on the ability to conduct electrical current via free electrons in metals or ions in solution (on the core)

Tarnish

A surface discoloration on a metal or a slight loss or alteration of the surface finish or luster. (On top only

Chemical corrosion

The direct combination of metallic and nonmetallic elements to yield a chemical compound through oxidation reactions.

Electrochemical corrosion

Also known as galvanic or wet corrosion, it requires a fluid electrolyte and a pathway for the transport of electrons.

also referred to as wet corrosion, since it requires a fluid electrolyte.

Galvanic shock

A sharp pain resulting from a sudden short-circuit when two restorations of dissimilar metals are brought into contact.