PCD Spring 2024 Exam 1
Indications of RBC
Caries lesions (small to moderate)
Esthetics (tooth color)
Conservative (outline, shallow, round)
Replacements of composites (questionable)
Advantages of RBC
Esthetics
Conservative
Adhesion to tooth structure
Low thermal conductivity
Elimination of galvanic issues
Alternative to amalgam?
What is necessary in amalgam preps?
90 degree CSM
Reverse curve
Adequate depth
Buccal/lingual convergence
Rounded internal line angles
Retention form
What is necessary in composite preps?
Bonding (needs a dry field)
Maintaining as much tooth structure as possible
What do amalgam preps have that composite preps don't?
Retentive features
Groove extensions
Convergent walls
Dovetail
Reverse curve
Axial wall
The internal wall that runs parallel to the long axis of the tooth
Gingival floor
floor of the prep that is closest to the gingiva
Axial wall height is determined by
Proximal contact
Rubber dam isolation is used to
Isolate/define the operating field by isolating one or more teeth from the oral
environment
Advantages of rubber dam
Moisture control
Access and visibility
Harm prevention
Contamination
,Conditions that may prevent the use of a rubber dam
Teeth that are not erupted enough
Malpositioned teeth
3rd molars
Pts that cannot breathe through nose
Psychological reactions
Properties of ceramics
Esthetics ++
Brittle
Properties of metals
Not esthetic
Strong
Properties of polymers
Esthetics +
Versatile
What is polymethyl methacrylate and what is it used for?
A polymer
Denture bases
Temp crowns
What is polyvinylsiloxane used for?
Impression materials
What things are resin with ceramic filler?
Resin composite restoratives
Adhesives
Cements
Type of bonds in polymers
Covalent bonding
Covalent bonding
Sharing of electrons
Equal tendencies to donate or accept electrons
What elements are involved in covalent bonding?
Carbon and silicon
What are the primary bonds in polymers?
Covalent
+ crosslinking
What are the secondary bonds in polymers?
Van der waal
Hydrogen bonds
Thermoplastic
a material that softens when heated and hardens again when cooled
Thermoset
when exposed to high temperatures, bonds are set, can't be unlocked
Resistant to change in shape with heating
Example of thermoplastic polymer material
The plastic material used to make bleaching trays/athletic mouthguards
Polymethyl methacrylate (PMMA) is an...
, Acrylic resin
Is PMMA thermoset or thermoplastic?
Thermoset
Heat curing mode activator and initiator
No activator
Initiator: benzoyl peroxide
Chemical curing mode activator and initiator
Activator: amine
Initiator: benzoyl peroxide
Light curing mode activator and initiator
Activator: camphoroquinone
Initiator: DMAEMA (amine)
Steps in polymerization
Initiation
Propagation
Termination
Why can't we use PMMA as a restorative material?
It is not easy to handle
It can't handle light (not esthetic)
It absorbs water, coffee, tea, etc.
Shrinkage
Mechanical properties
Composite
A compound of two or more distinctly different materials with properties that are superior
or intermediate to those of the individual constituents
Composite structure has what two phases?
Dispersed phase
Matrix phase
Dispersed phase=
Glass fiber
Matrix phase=
Epoxy resin
Three components of dental resin composite
Dispersed phase
Matrix phase
Coupling agent
Coupling agent=
Silane
Filler loading
The volume percent of filler particles vs resin matrix in the composite material
The mechanical properties and clinical characteristics of dental resin composite
materials are primarily determined by the
Volume percent of filler loading
As the % filler vs resin increases...
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