CHAPTER 43 Flashcards
must withstand biting and chewing forces
mechanical
any push or pull on matter is called
force
types of stress and strains
tensile
compressive
shear
pulls and stretches material. two forces applied in different difrections
tensile stress
two forces applied in the same direction (ex: chewing is a type of this stress)
compressive stress
two forces of material parallel to each other sliding in opposite directions. ex: clenching teeth, bruxism
shear stress
the measure of the capacity of a metal to be stretched or drawn out by a pulling or tensile force without fracturing
ductility
the most malleable metal
gold
change in temp in the oral cavity resulting from ingesting hot or cold products leads in size changes in the material. Will result in expansion and contraction.
thermal changes
happens when there are two different kind of metals inside the patients mouth
electrical properties / galvanic shock
the mechanical property of a dental material. A permanent restoration must have enough _______ to resist indentation, scratching, or abrasion
hardness
the reaction that occurs within a metal when it is exposed to corrosive factors such as temperature, humidity, and saline.
corrosion
the degree to which a substance will dissolve in a given amount of another substance
solubility
measure of the capacity of a metal to be stretched or drawn out by a pulling or tensile force without fracturing
ductility
measure of the capacity of a metal to be extended in all directions by a compressive force, such as rolling or hammering.
malleability
thermal changes are of major concern for two reasons
- contraction and expansion
2. need to protect pulp from thermal shock from extreme differences in temp.
It is essential that the tooth structure and the restorative material have, as nearly as possible, the same ____ of contraction and expansion.
rate
conditions that cause galvanic shock
two different metal composition in the mouth
saliva = good electricty conductor
The surface discoloration that we see in older amalgam restorations in the mouth is referred to as
tarnish
For a dental material to have specific mechanical properties, steps must occur in the application of the dental material. Techniques used in the placement help create the following effects.
flow
adhesion
retention
curing
the ability of two unlike materials to
adhere to each other.
adhesion
Characteristics of a dental material that will affect the adhesion process
wetting,
viscosity,
surface characteristic
film thickness
the ability of a liquid to come into contact with a solid surface, and the small irregularities that may be present.
wetting
is the property of a liquid that causes it not to flow easily.
viscosity
is the ability to hold two things firmly together when they will not adhere to each other naturally.
retention
a setting process of a dental material that is initiated by a chemical reaction or by a light in a blue wave spectrum
curing