Dental Materials

porcelain restorations have
A. great stain resistance
B. no disadvantages
C. low wear resistance
D. easy reparability

porcelain bonds to metal by which one of the following mechanisms
A. shrinks when it is fired and locks itself onto metal
B. penetrates the surface of the metal
C. fuses to oxides on the surface of the metal
D. micromechanical retention such as resin to etched enamel

the main advantage of all ceramic crowns over porcelain bonded to metal crowns is
A. their strength
B. teh ease of taking shades
C. their ease of cementation
D. their superior esthetics

the main drawback of feldspathic porcelain for all porcelain crowns is
A. their tendency to fracture
B. the difficulty involved in making them
C. the shrinkage when fired makes them difficult to fit the prepared tooth
D. their opacity

an in offic CAD/CAM system for cermaic restorations provides all of the following advantages except one:
A. a provisional crown is not needed
B. the procedure can be completed in one visit
C. the restoration does not have to be fabricated in an outside lab
D. local anesthesia is not needed

the basic color of the tooth is called?

all of hte following should be avoided when taking the shade of a tooth except one:
A. lipstick on the pt
B. dirty teeth
C. neutral wall colors in the rooms
D. brightly colored clothing

all of the following materials should be avoided around ceramic restorations except one:
A. acid etchant
B. coarse prophy paste
C. acidulated topical fluoride
D. alginate impression material

the impression for a CAD/CAM crown is
A. done with polyether imprssion material
B. done with alginate
C. done wtih polyvinylsiloxane impression material
D. done by capturing an image of the prepared tooth with an optical scanner

when preparing a procelain fused to metal crown the technician applies feldspathic porcelain in layers to hte metal copin. this initial layer is
A. body porcelain to mimic dentin
B. opaque porcelain to hide the oxidized metal
C. translucent procelain to mimic enamel

occasionally special porcelain stains are used on the surface of porcelain. these stains contain metal oxides and are used to
A. hide flaws created in the porcelain by firing it at high temperatures
B. create a shiny, smooth surface
C. mimic white spots or fine crack lines to resemble adjacent teeth

which one of the follwing statments about porcelain vaneers is false
A. it is difficult to mask a darkly colored tooth with a porcelain veneer
B. porcelain veneers must be handled carefully when one is trying them in because they are very fragile until bonded to the tooth
C. porcelain veneers are usually cemented with zinc phosphate or glass ionomer cement
D. porcelain veneers are more durable than composite veneers

when assisting the dentist with taking the shade of a tooth the dental assistant should
A. dry the teeth thoroughly
B. stare at teh tooth and shade guide intensely for at least 30 seconds to let the eyes adjust to the colors
C. shine the operatory light directly on the teeth
D. cover brightly colored clothing with a pastel neutral colored bib

when one istaking photographs of the teeth to send to the dental laboratory to help convey the correct shade, what is the proper ocation for the shade tab in the photograph?
A. outside the mouth
B. inside the mouth in front of the teeth
C. in the same plane as the tooth being matched
D. non of the above (the shade tabe does not have to be included in the photograph