Ch 43 Flashcards
Restorative
the ability to remove decay or disease and bring proper function back to the tooth
Esthetic
the recreating the tooth or teeth with an artistically pleasing appearance
Criteria for a new dental material
It must not be poisonous or harmful to the body
It must not be harmful or irritating to the tissues of the oral cavity
criteria for new dental material
It must help protect the tooth and oral tissues of the oral cavity
It must resemble the natural dentition as closely as possible so as to be esthetically pleasing.
criteria for new dental material
It must be easily formed and placed in the mouth
It must conform to function
The Council on Dental Materials, Instruments and Equipment, a subcommittee of the American Dental Association,
works with federal agencies to ensure that strict specifications are followed by manufacturers in the development of new dental materials.
The following characteristics enhance the ability of dental materials to withstand the oral environment and allow for easy application….
Mechanical properties
Thermal changes
Electrical properties
Corrosive properties
Solubility
Application properties
electrical and corrosive properties are…
important with metallic restorations
thermal insulation is desirable for example…
under an extensive restoration and under a denture base we would like thermal transfer.
mechanical properties
Materials must be able to withstand the biting and chewing force in the posterior area of the mouth.
force
any push or pull on matter
stress
the reaction within the material that can cause distortion
strain
the change produced within the material that occurs as the result of stress
A restoration will eventually reach a breaking point…
causing permanent deformation (change) after a certain amount of both stress and strain is applied over a certain amount of time.
Mechanical properties of a material placed in the anterior area should also withstand various forces caused by factors,
including occlusion and a patient’s habits.
Remember that different materials have different properties
under different types of force
tensile stress
pull and stretches the material
compressive stress
pushes the material together
shear stress
breakdown of the material as the result of something sliding over 2 areas
a patient enjoys eating sticky candy
tensile stress
a patient reports clenching his teeth when he is concentrating hard at work
compressive stress
a patient has a habit of grinding her teeth at night or nocturnal bruxism
shear stress
ductility
the measure of the capacity of a metal to be stretched or drawn by pulling or tensile force w/o fracturing
malleability
the measure of the capacity of a metal to be extended in all directions by a compressive force, such as rolling or hammering
thermal changes
A change in temperature in the oral cavity resulting from a hot or cold product.
These thermal changes are of major concern because of
Contraction and expansion
The need to protect the pulp from thermal shock from extreme differences in temperature
When the restorative material and surrounding tooth structure have different rates of contraction and expansion, ______ may occur
microleakage
Space between the tooth and the restoration allows _____or_______ to enter, causing sensitivity and/or breakdown of that interface and ultimately destroying the restoration and permitting decay in the tooth.
saliva or bacteria
Space between the tooth and the restoration allows saliva or bacteria to enter, causing _________ of that interface and ultimately destroying the restoration and permitting decay in the tooth.
sensitivity and/or breakdown
Space between the tooth and the restoration allows saliva or bacteria to enter, causing sensitivity and/or breakdown of that interface and ________________
ultimately destroying the restoration and permitting decay in the tooth.
what does galvanic shock feel like ?
an undesirable tingling sensation
Conditions that allow these electrical currents include:
Saliva contains salt, a good conductor
Two metallic components of different composition can act as a battery
Galvanic action, or shock,
Galvanic action, or shock…
is the coming together of all these conditions
An electrical current, or galvanic action, in the oral cavity can take place ….
when there are two different or dissimilar metals present.
One patient who may report such a feeling is someone who has teeth on opposing arches that contact each other in function….
The teeth contain restorations composed of different metals (e.g., a full gold crown opposing a large amalgam).
Corrosive properties
The reaction of metals that occurs within a metal when it is exposed to corrosive products such as temperature, humidity and saline
Most corrosion involves surface discoloration and can be removed easily with the use of
polishing agents
What common drinks or foods have corrosive properties?
Soft drinks, concentrated lemonade, and other products that create a highly acidic oral environment.)
Plaque that remains for an extended period on the margin between an amalgam and the tooth may also produce…
a more acidic environment locally
An acidic environment (lactic acid under dental plaque)
drastically changes the solubility of tooth structure, such as enamel.
Because enamel is the hardest substance in the body,
the plaque must have been present for a considerable amount of time for a cavity to occur
solubility
The degree to which a substance will dissolve in a given amount of another substance
sand has low solubility bc..
it does not dissolve easily
sugar has high solubility bc…
it does dissolve easily
The mouth is exposed to many kinds of acids,
which can dissolve materials
many sodas and sports drink have a very _____ pH
acidic
Citric acid is added to many food to give them….
a tart taste
For a dental material to have specific mechanical properties, steps must occur in the
application of the dental material
What are the different properties of dental materials that may affect the application properties?
(Flow, adhesion which includes wetting and viscosity, retention, and curing.)
flow
dental materials are designed to have a certain amount of flow for placement
this allows the material to fill in the preparation of the tooth
flow
When ______ that help prevent decay are placed on newly erupted permanent molars that are deeply fissured,
sealants
the sealant material ___________ to plug up and protect areas that are not easily cleaned.
must flow well
adhesion
the strength that causes unlike materials to adhere to each other
without proper adhesion,
micro leakage can occur and restoration could come out
Characteristics of dental materials that can affect the adhesion process are:
wetting, viscosity, surface characteristics, film thickness
wetting
ability to flow over a surface
viscosity
property of a liquid that causes it not to flow easily
surface characteristics
influence the wetting ability
film thickness
thinner means stronger adhesive junction
adhesion may be thought of as placing….
tape on paper
hydrophilic
water loving
hydrophobic
water hating
a hydrophilic surface would not wet well by a…
hydrophobic liquid
A consideration in wetting is whether two materials are ……
hydrophilic (water loving) or hydrophobic (water hater)
example of ideal film thickness
think of piecing together a broken china ornament using Krazy Glue rather than the thicker glue used in grade school craft projects.
retention
The ability of holding two things firmly together when they will not adhere to each other naturally
Even though retention holds the material in place,
it does not completely seal the two structures together.
_________ can occur if an additional material such as a bonding material is not placed to create a seal.
microleakage
Microleakage can occur if an additional material such as a ___________ is not placed to create a seal.
bonding material
________ is very important in the preparation of teeth that are to receive amalgam fillings.
retention
Retention is very important in the preparation of teeth that are to ____________________
receive amalgam fillings.
One of the ways in which retention is achieved is preparing ….
the opposing inside walls of the tooth to slant slightly inward
One of the ways in which retention is achieved is preparing the opposing inside walls of the tooth to slant slightly inward so
that when amalgam is placed and set it will not slide out.
there are 2 types of retention….
mechanical and chemical
The application of sealant is an example of …..
mechanical retention
The _______ increases the surface area for retention and the sealant material flows into all the nooks and crannies on the surface of the tooth.
etchant
curing
A setting process of a dental material that is initiated by a chemical reaction or by light in a blue wave spectrum
auto cured
material hardens as a result of a chemical reaction of the materials once mixed together.
light cured
material does not harden until it has been exposed to a curing light.
dual cured
material, some curing takes place as the material is mixed. The final cure does not occur until the material has been exposed to a curing light.
Bonded materials are set (hardened) by various means, including exposure to light of a particular ______. chemical reaction (auto), or a combination of the two.
wavelength
Bonded materials are set (hardened) by various means, including exposure to light of a particular wavelength, _____________ , or a combination of the two.
chemical reaction
Bonded materials are set (hardened) by various means, including exposure to light of a particular wavelength, chemical reaction (auto), or _______________
a combination of the 2
What is an example of a dental material that has been the subject of a lot of public discussion about its safety?
amalgam, due to the mercury content, and other alloys
