The goal of the dentistry is to maintain or improve the quality of life of the dental patients. This goal can be accomplished by preventing disease, relieving pain, improving mastication efficiency, enhancing speech and improving appearance.
The four groups of materials used in dentistry today are metals, ceramics, polymers and composites.
An ideal restorative material would be
It is a process of roughening a solid surface by exposing it to an acid and thoroughly rinsing the residue to promote micromechanical bonding of an adhesive to the surface
When two substances are brought i9nto intimate contact each other, the molecules of one substance adhere or attracted to, molecules of the other substance. This force is called as adhesion. Adhesion may occur as a chemical or physical or a combination of both types
Force of molecular attraction between molecules or atoms of the same species.
It is defined as the change in length per unit of the original length of a material when its temperature is raised 1 degree kelvin
Stress is defined as an internal force opposing an applied load.
Compressive stress:- internal resistance to a load that tends to compress or shorten a body
Tensile stress:– internal resistance to a load that tends to stretch or elongate a body
Shear stress:- a stress that tends to resist a twisting motion, or a sliding of one portion of a body over another is a shear or shearing stress
Strain is defined as a deformation resulting from an applied load. Strain has no units to measure
It is defined as the maximum stress that can be induced without permanent deformation
Stress/strain ratio within the proportional limit is called elastic modulus or young’s modulus. It measures the relative rigidity or stiffness of material
Macro hardness tests:- Brinnel and Rockwell tests are classified as macro hardness tests and they are not suitable for brittle materials
Micro hardness tests:– the Knoop and Vickers tests are classified as micro hardness tests. Both of these tests employ loads less than 9.8 N
The SHORE and the BARCOL tests are used for measuring the hardness of rubbers and plastics
After the dentist has completed a tooth preparation for a filling, tenacious microscopic debris covers the enamel and dentin surfaces. This surface contamination, called the smear layer.
Time-dependent plastic strain of a material under a static load or constant stress
Flow is the deformation under a small static load even that associated with its own mass. Flow describes the behavior of amorphous material such as waxes.
Dominant color of an object
Relative lightness of darkness of a color
Degree of saturation of a particular hue
The ability of a material to resist abrasion or wear
Relative ability of a material to deform plastically under a tensile stress before it fractures
It is the ratio of elastic stress to elastic strain
Deformation that is not recoverable when the externally applied force is removed
Chemical or electrochemical process in which a solid; usually a metal, is attacked by an environmental agent, resulting in partial or complete dissolution.
Surface discoloration on a metal, or as a slight loss or alteration of the surface finish or luster
Resistance of a fluid to flow