materials placed in the oral cavity must be what 5 things?
biocompatible
durable
nonreactive in acid or alkiline conditions
compatible with other materials
esthetically acceptable
What are 5 environmental factors that affect the compatibility or materials?
moisture
stresses
termperatures
acid levels
time/how long materials are expected to be used
Therapeutic agents are generally used for _______ periods of time, where as restorative agents are expected to remain in contact with tissues for ________ lengths of time
short
indefinite
What is an example of a material that is therapeutic in small quantities but may be irritating or toxic with longer or larger doses?
topical fluoride
true or false. All materials contain potentially irritating ingredients
true
Dentists must consider the performance of a material on the basis of knowledge of its ________ and the intended ________ of the material
properties
application
Much as an engineer would do, a dentist must design a bridge while taking into consideration what 3 structures?
load
span
supporting
What are 3 different types of forces that materials must be able to withstand in varying degrees of force or load?
mastication (cushioned by food)
bruxing
clenching
Normal masticatory forces on the occlusal furfaces of molar teeth average ____ to ______ pounds; and can increase to as much as ______ pounds per square inch on a cusp tip
90
100
28,000
Masticatory forces are ________ in incisor areas
decreased
each tooth is ideally suited for specific types of _________
force
That are the 3 basic types of masticatory force?
compressive
tensile
shearing
force applied to compress an object. Posterior teeth are ideally suited for this type of force.
compressive
Why are posterior teeth ideal for compressive force?
because of the large occlusal surface and the multi-rooted base; it will resist a crushing force
force applied in opposite directions to stretch an object, when biting forces are used to stretch a material the tooth is exerting this type of force
tensile
force applied when two surfaces slide against eachother or in a twisting or rotating motion. An incisor used for cutting is an example of this
shearing force
When a force is exerted on a tooth, the tooth or material creates resistance to couteract the force. This INTERNAL force, which resists the applied force is called what?
stress
amount of change or deformation the force prodecued, ie. distortion or deformation
strain
true or false. teeth have flexure and implants don't.
true
______ and _______ _______ more closelly replicated enamel in compressive strength, but _________ falls short.
amalgam
composite resins
porcelain
a metal wire bent repeatedly will eventually break, this is an example of what?
fatigue failure
true or false. humidity, temperature, and pH fluctuations may increase fatigue failure.
true
What is the normal resting pH of saliva?
6.2-7.0 neutral
the breakdown of most restorative materials is directly related to the effects of ________, __________, and ___________
moisture
acid
stress
Why are gold and porcelain retained in the oral environment for many years?
because of their insoluble nature
What are 4 examples of acid or alkiline that the oral cavity is continually in contact with?
food
beverages
medicines
plaque bacteria
desireable materials to use have what 2 qualities that have to do with moisture and acid levels?
low solubility
low water sorption
Staining of resins and acrylics from repeated exposure to coffee, tea, and other dyed beverages is due to what?
water sorption
What factors make electrical current possible in galvanism? (3)
moisture
acidity
dissimilar metals
the phenomenon of transmission of electrical current between 2 dissimilar metals
galvanism
Pulpal stimulation from the electric current in galvanism
