Identify three national and two international organizations that develop or regulate criteria for materials used in dentistry and explain their roles.

National

      1).  American Dental Association’s council on Dental Materials, and ADA Specification and Acceptance Program

      2). National Institute of Standards and Technology (Bureau of Standards)

            3). Food and Drug Administration -On May 28, 1976, legislation was signed into law that gave the U.S. Food and Drug Administration (FDA) the regulatory authority to protect the public from hazardous or ineffective medical (and dental) devices.

      4). Occupational Safety and Health Agency

      5). Center for Disease Control

      International

            1). Federation Dentaire Internationale (FDI) - the FDI initiated and actively supported a program for the formulation of international specifications for dental materials. As a result of that activity, several specifications for dental materials and devices have been adopted.

            2). International Standards Organization (ISO) - The ISO is an international, nongovernmental organization whose objective is the development of international standards. This body is composed of national standards organizations from more than 80 countries. 

List several factors that limit the choices of materials that can be selected by dentist for clinical laboratory use. (name at least 8)

1). Strength comparable to natural teeth

      2). Affordability

      3). Biocompatibility

      4). Ease of Use

      5). Stable in the oral environment

      6). Esthetics

      7). Non toxic

      8). Durable

Characterize the three basic materials used in restoring and rehabilitating the oral cavity in terms of their physical and mechanical properties.

1). Ceramics – inorganic salts, crystalline ceramics, glasses

      2). Metals – alloys and intermetallic compounds

      3). Polymers – rigid polymers, waxes, elastomers

*4) Composites

Explain the differences between amorphous and crystalline structures and give examples of each?

Amorphous materials such as waxes and resins appear solid but actually are supercooled liquids that can flow plastically (irreversibly) under sustained loading or deform elastically (reversibly) under small stresses.

            Atoms are bonded to each other by either primary or secondary forces. In the solid state, they combine in a manner that ensures minimal internal energy. For example, sodium and chlorine share one electron, as previously described. In the solid state, however, the atoms do not simply form only pairs; in fact, all of the positively charged sodium ions attract all of the negatively charged chlorine ions. The result is that they form a regularly spaced configuration known as a space lattice or crystal. A space lattice can be defined as any arrangement of atoms in space in which every atom is situated similarly to every other atom. Space lattices may be the result of primary or secondary bonds.There are 14 possible lattice types or forms, but many of the metals used in dentistry belong to the cubic system; that is, the atoms crystallize in cubic arrangements. The simplest cubic space lattice is shown in Figure 2-10, with the spheres representing the positions of the atoms. Their positions are located at the points of intersection of three sets of parallel planes, each set being perpendicular to the other two sets of planes. These planes are often referred to as crystal planes. All dental amalgams, cast alloys, wrought metals, gold foil, and dental amalgam are crystalline. 

Explain stress and its relationship to strain?

[image]Restorative Dental Materials:  materials used to restore or repair tooth structure.  There are direct (manipulated intra-orally and given to the patient immediately) and indirect (materials that are used extra-orally to replace or repair tooth structure and are either fabricated in the office, but outside the mouth, or in the laboratory) restorative materials.

Preventive Dental Materials:  materials used to seal pits and fissures in teeth so as to prevent the formation of caries, or materials that give off a therapeutic agent such as fluoride or chlorohexidine which help to prevent the demineralization of tooth structure.

[image][image][image]Biocompatible

[image][image][image][image]Initiates tissue/tooth re-growth and repair

[image][image][image]Bonds completely to existing structures

Matches the natural structures

Exhibits similar properties to natural tissues (enamel, dentin, cementum, other oral tissue)

Esthetics

Non-toxic

Durability

Biocompatibility

Affordability

Strength

Ease of use

Stability in the oral cavity