robbypowell's version from 2016-09-19 03:24


Question Answer
_____ _____ is the reason for the discrepancy between theoretical and actual strengths. Small surface flaws focus stress at the tips of defectsStress concentration
_____ creates a “pulling” force on the surfacetension
Brittle materials (such as ceramics) tend to be weak in _____ and are easily pulled aparttension (tensile strength)
Why don't dislocations in ceramics work the same way as metals (molecular level explanation)ceramics made up of positive and negatively charged crystalline structure, so when like charges are dislocated together, they cannot re-bond
T/F: Surface smoothening is an important strengthening quality of ceramicsTrue (less stress concentrations)
Glasses and ceramics have very high ____ strength and very low _____ strengthhigh compressive, low tensile
Residual compressive strength is often imbued to glasses on the outside by chemically changing some of the surface ____ ions with ____ ionsNa replaced with Potassium
____ _____ mismatch can be used to imbue greater strengths by stacking different layers of different glass/ceramic material because of residual compressive strength caused by differences between diff types of glassThermal Expansion mismatch
what type of line angles are preferable for preparations to be covered by all-ceramic crowns?rounded line angles (less stress concentration)
Glass modifiers affect melting temp how? durability how?lower melting temp; lower durability
which is more preferable for a porcelain crown... self-glaze or applied glaze?self-glaze (greater durability)
what is the Naturally occurring mineral composes of potash, alumina, and silica that is Used in nearly all PFMs.Feldspar
main component of dental porcelainsFeldspar
How are porcelain teeth retained in denture base?Mechanical interlocking (locked in or with pins)
How is porcelain-metal bond formed (in PFM's)Base metals form oxide layer during degassing, this allows for chemical bond to porcelain (without mechanical retention)
Dense packing allows for _____ (more/less) firing shrinkage and ___ (more/less) porosity in the fired porcelainLess; Less
Vacuum is used (about 1/10th of normal atmospheric pressure) during porcelain firing to reduce _____Porosity
_____ reduces translucency of porcelain and is undesirable. it scatters light and make it appear more opaque and possibly affects the strengthPorosity
t/f: polishing may be more effective than glazing, for reducing stress concentration on porcelainTrue

porcelains or types of processing porcelain

Question Answer
One distinguishing feature of ______ is that it Uses net shape processing to produce ceramics with very low processing shrinkage to produce ceramic articles that are the same size and shape as the patterns from which they are madeIn-Ceram
Conventional impressions and gypsum dies with Alumina frameworks used for _____Procera
with _____ Uses optical impressions after a reflective powder is coated on the prepared tooth. Then crown is milled out of a solid block of ceramicCEREC
with _____ Uses a wax pattern and heat pressed ceramic injection into a moldEmpress
with _____ an Optical scan of a conventional die system is used. Coping is then milled and veneered with hand stacked porcelainLava
Porcelain is typically repaired with ____ _____ with a _____ coupling agentResin Composite; Silane (coupling agent)
Degussa developed _____ (low-fusing porcelain) that has a lower melting range than conventional ceramics. Normally this means lower resistance to dissolution in oral fluids but this kind is hydrothermal. NOT designed for application directly to metal but for over metal ceramic porcelainDUCERAM