Exam 1 Flashcards
What is an abutment?
- part of a structure that directly receives thrust or pressure
- a tooth/portion of a tooth or that partion of a dental implant that serves to support and/or retain a prosthesis
What is a retainer?
-any type of device used for the stabilization or retention of a prosthesis
What is a pontic?
-an artificial tooth on a fixed dental prosthesis that replaces a missing natural tooth, restores its function, and usually fills the space previously occupied by the clinical crown
What are the main biologic considerations for an FDP?
- prevention of adjacent tooth damage, soft tissue damage or pulpal injury
- conservation of tooth structure
- future dental health
What are the mechanical considerations for an FDP
- retention
- resistance
- preventing deformation of the restoration
What are the esthetic considerations for an FDP?
- all ceramic
- metal ceramic
- material considerations
What are some of the main ways to conserve tooth structure?
- partial coverage crowns
- minimum practical convergence angle
- follow anatomic planes to give uniform thickness
- selection of conservative margin geometry
- avoid unnecessary apical extension of the preparation
Porcelain margins can be finished to what closeness of cement?
-50 micrometers
What issues are created by irregular/rough margins?q
-reduction of adaptation accuracy of restoration
What are the benefits of supragingival margin placement?
- no soft tissue trauma
- easy to clean
- easier impression
- easy to evaluate
What are conditions requiring a subgingival margin?
- dental caries, cervical erosion, or esthetic zone
- proximal contact extends to gingival crest
- additional retention/resistance needed
- root sensitivity
- associated with RPD
What are the advantages of diagnostic casts?
- for fixed restorations
- fabrication of provisionals
- fabrication of custom trays
Mounted diagnostic casts are used for what?
- evaluation of occlusal plane
- interarch clearance
- treatment position
- change in VDO
- occlusal analysis
- esthetic analysis
What are the three components of retention?
- taper
- length
- surface area
What is total axial convergence?
-sum of the taper of two opposing preparation walls
What is the sloped shoulder margin design used for?
- PFM crowns FPD
- no metal collar
- improved esthetics
- less intrusion into gingival crevice
- simple laboratory construction
What are the disadvantages of a sloped shoulder?
- more difficult preparation
- greater marginal creep
- rough marginal area
- potential gray line
- lab tends to overcontour
- higher lab cost
What are the absolute indications of the porcelain butt margin?
- minimal sulcus depth of 1mm or less
- thin labial tissue
- high smile line
What are the real indications of the porcelain butt margin?
- margins in the esthetic zone
- which is where the patient says it is
What is ante’s law?
- in order to maintain a stable FPD, there are several considerations
- the total periodontal membrane area of the abutment teeth must equal or exceed that of the teeth to be replaced
- extensions of the primary abutment must correspond to the distance of the lever arm that the pontics exert
For extended restorations, what are some options in order to not have an FPD fail?
- non-rigid connectors
- cantilever pontic
What are ceramics?
-products made from a non-metallic inorganic material processed by firing at high temp to achieve desirable properties
First porcelain jacket crown by Pierre Fauchard was made when?
-1800
First ceramic crown was introduced by charles lind when?
-1903
Which fusion groups of dental ceramics are used for denture teeth and porcelain jacket crowns?
-High and medium fusion 1090-1370*C
Which fusion groups of dental ceramics are used for metal ceramic crowns?
-Low and ultra-low fusion <1070*C
What is feldspar?
- naturally occurring glass that contains silica, fluxes and alumina all neatly bound together
- fused @ high temp
What is a frit?
-small fragments generated by the fracture of dental porcelain when Feldspar, quartz and other oxides are heated @ high temp
How thick does the metal for the FDP have to be?
-0.5mm
Metal surfaces are prepared to receive porcelain with what grinding stone?
-pink
How are metal crowns oxidiized?
-fired in air in oven 1200-1900*F
What are the 3 types of porcelain particles used in MCCs?
- opaque- containing opacifying oxides
- body/dentin porcelain- translucent and contains metal oxides that give base color selected
- incisal/enamel- more translucent than body porcelain
What is the process of opaque application?
- mix paste, apply with paintbrush and bake
- bake @ 1800*F 1min under vacuum
What burs are safe for the adjustment of metal ceramic and ACC?
-low speed handpiece with stones or diamond burs designed for porcelain
What do you have to do before the 2nd bake?
-clean crown in ultrasonic and add porcelain to deficient areas
What are the advantages to the porcelain labial margin?
- improve esthetics
- less plaque retention
What are the disadvantages to the porcelain labial margin?
- inferior marginal adaptation compared to cast metal
- decreased strength
- more time consuming/difficult
- more expensive
What are the advantages of the direct lift technique?
-least time consuming
What are the disadvantages of the direct lift technique?
- shoulder porcelain needed
- slightly rough margins
What is a lucia jig?
used to maintain VDO in CR
like an incisal guide table
What is the main reason for FPD failure?
-Caries
What are the main considerations for success of the FPD?
- minimize sliding contacts
- establish anterior guidance
- have opposing contacts in same material
- control parafunction
What is the distance from the junction between two materials that occlusal contacts have to be?
-1.5 mm
What is the mechanism for glass-to-metal bonding?
- glass will adhere to clean, gas-free metal if covered with adherent oxide and temperature raised where oxide is partially dissolved into glass
- strain free if coefficients of thermal expansion are the same over the entire temperature range
What is adhesive failure @ the porcelain metal interface of an MCC?
-happens @ porcelain metal interface due to missing oxide layer (lab problem)
What is adhesive failure @ metal-oxide - metal interface due to?
-contaminated metal (lab problem)
What is adhesive failure at the porcelain - metal-oxide interface due to ?
-contaminate metal oxide (lab problem)
What is cohesive failure in the porcelain due to?
-maximum strength reached (patient problem)
What is cohesive failure in metal oxide due to?
-excessive oxidation (lab problem)
What are the key characteristics of framework design?
- even porcelain thickness (established by waxing)
- rounded internal angles
- 90* metal/porcelain junction
- Porcelain wrap around
- metal thickness at least 0.3 mm
