Dental Materials Test 1 Flashcards
Amount of force applied to a specific area
Stress=force/area
What base is still used: stimulate dentin formation and ph raises as it dissolves
calcium hydroxide
Internal rearrangement of atoms to adjust to the stress-deformation results
Strain=deformation/length
Forces on object directed away from each other - stretched or elongated…ability of an object to resist pulling
Tensile
Resistance in the material to the external force - ability to resist pushing
Compressive
Ability to resist tearing - forces directed parallel to each other. Occurs when one portion of a structure is forced to slide by another portion (i.e.. scissors)
Shear
Stiffness of material, maximum stress w/o permanent deformation. Material can’t regain its size and/or shape
Elastic limit - proportional limit
Point just before fracture
Ultimate strength
Ability of material to be drawn into a wire
Ductility = elongation
Low ductility = brittleness
Ability to be hammered or rolled into thin sheets without fracture- compression
Malleability
Energy necessary to cause permanent deformation
Resilience
Ability of material to resist fracture
Toughness
Gradual permanent change in dimension that occurs in an object due to constant loading
Flow after set (amalgam)
Creep
Resistance of material to flow
Viscosity
Some materials have a high viscosity but change w/pressure (mixing)…impression materials change thru manipulation
Thixotropic
Depth of an indentation made with a steel ball- composites ↕️
Rockwell (RHN) hardness
Measuring the length of a diagonal made with a diamond indenter- metals and porcelain ↔️
Knoop (KHN) hardness
The repeated application of stress to an object causing tiny cracks to be generated within the structure until failure occurs
Fatigue
Pt ed. for 12 year old who is going to play field hockey….
Mouthguard
How do cements look on an X-ray?
Opaque
Dental cement can be used as a base…
- Can it protect pulp?
- Adequate compressive strength?
- Is it a poor conductor of temp
Yes all of above
Most conservative tx for 43 yr old with extensive internal stains- finances not an issue
Veneers
New material should have hardened when light passed, but didn’t… you would say material did not what?
Cure
Which type of composite has the lowest viscosity
Flowable
Filler size and polishability, easier to polish what?
Microfilled
What releases Fluoride?
Glass ionomer
What function does kaolin perform in porcelain
Causes parameters to be cohesive when wet and it adds pigment
Bases help to do what with thermal conductivity?
Limit/eliminate
What do varnishes do?
Seal dentin tubules
What is the best base to use in a deep cavity prep
calcium hydroxide
Don’t use ZOE under a material that you want to what? (i.e. composite)
polymerize
Copalite is to what?
Seal dentinal tubules
What is created with high speed, debris of enamel and dentin
Smear layer
Pt with history of sensitive teeth, requires amalgam restoration of max molar which base material may be the best choice
glass ionomer
Base metal alloys are utilized to make what?
Crowns, bridges, PFM
Can glass ionomers be utilized as cements and restorations and bases?
Yes
Which are characteristics of glass ionomers?
release fluoride, bond to composite, enamel and dentin
Which element is most responsible for reacting with mercury causing amalgam to set up?
Silver
Pt. comes in with amalgam of equivalent age in 2 first molars, amalgam in #19 shows more marginal breakdown than the one in #30?
Both of these answers are correct
- amalgam in 19 is less corrosion resistant than 30
- amalgam in tooth 19 has higher creep than 30
Advantage of amalgam…
Easy to insert, manipulate, resists fracture
Corrosion effects the Cavo surface margin
True..(where amalgam and tooth meets)
What percent of gold is in 18 k gold?
75%
Compared to pure gold, dental gold alloys are:
Harder
Which type of porcelain is used in a porcelain fused to metal crown?
Low fusing (if it were high fusing it would melt the metal that has already been built on the prep. Tooth)
As a metal restoration ages micro-leakage does what?
Decreases because of the process corrosion (self seals)
Pt presents with well defined very red scalloped area along gingival margin, adjacent to base metal crown which of the following is not a cause…
-sub gingival crown margin
-nickel allergy
-galvanic reaction
Galvanic reaction
What restorations can be placed to provide healing time
ZOE
How can mercury enter body?
Inhaling, ingestion, across skin
Which setting phase of amalgam adds strength
gamma 1
Which phase is most detrimental
gamma 2
Similar to a filling, but indirect, contained within cusps, cemented
Inlay
Indirect restoration on the occlusal surface, includes a cusp, cemented or bonded
Onlay
Considered color name
Hue
Lightness or darkness of a color (hue)
Value
Vividness or strength of a color or hue (difference between 1 or 2 coast of paint)
Chroma
The way the light is affected when entering a substance
Translucency
Components of porcelain
Combo of Kaolin, feldspar, and quartz…porcelain is fired whereas ceramic is machine milled.
