readings Flashcards
is the MCC considered to be conservative
No
what was an inital problem with MCC
Finding a way to bond metal and ceramic
what are the charcteristics of the metal in a MCC
higher fusing range
Lower thermal expansion
Indications for MCC
need complete coverative esthetics
need for use in fixed dental prosthetics
similar to cast metal crowns
why can MCC be used in fixed dental prosthetics
because it can be a retainer due to its metal substrat to be cast or solfered connected
similar to cast metal crowns
MCC contraindications
active caries
untreat perio disease
large pulp cambers
when a more conservative restoration is better
can an MCC have a brittle fracture
Yes, because of ceramics
is the MCC expensive
yes
what is important for an impression to get
- sufficient unpreparaed tooth structure immediately adjacent to the margin for the dentist and lab to identify contour of the tooth and all prepared surface
- need to know contour
- all teeth in arch
- immediate soft tissue surrounding the prep
- lingual surface of anterior teeth (lingual guidance)
why is it hard to get a good impression
wet (gives voids)
are elastomeric impression hyrophilic or phobic
Phobic except for polyethrers
what must be done if you go subgingivally
move gingiva using mech, chem, and surgical means without jeopardizing perio health
what can lead to permanent soft tissue damage
improper manipulation of impression
poor tissue displacement technique
probem with bad interums( bad contour, polished poorly, bad margin, plaque retention)
if you injury soft tissue, it won’t be able to heal properly
- inflammation
can you do fixed with perio disease
No, perio should be solved first
what do you do if the fixed restoration is done before you and causes perio problems
Place an interum, fix perio, then new crown
how to control saliva in the maxillary arch
cotton roll in vestibule buccal to prep
saliva evacuator on the lingual
what happens when part of the cotton roll is saturated
Entire roll must be replaced
how do you control the tongue on the mandible
flange type evacuator using cotton rolls to minimize discomfort between the mylohyoid ridge of the alvelar prosses
anesthetics effect on saliva
slows saliva cuz pdl nerve impulses lead to saliva flow
drugs to control saliva
Anti-cholinergics (rarely used
what is used for mechanical displacement of gingiva
chord
also paste system in conjucntion with directed pressure
chem (aluminum sulfate and epinephrine) shrink the tissue)
cutting sergically
what type of cord is used to displace gingiva
Non-impregnated cord
what does the cord do
stretches the circumferential PDF
Shrinkage of gingival tissue
Ischemia
why would cord have metal filaments
maintain intrasulcular position
how fast does the sulcus close after cord removal
30 seconds (fast)
what to avoid when using astringent
low pH can affect the preped tooth a lot (smear layer and demineralization)
what do you do if you place the cord in dry
GEt it wet to avoid tearing when it is removed
where is the best place to first place the cord
In the interproximal areas
why might it be hard to place cord
Ginvial inflammation (bleeds easy, swollen)
How do you know you have the correct amount of cord
See the margin circumferentially
uninterrupted cord with no soft tisssue folded over it
sizes of cords for the double cord technique
1st in is small and left in for the impression
2nd in is larger and removed for impression
how to control minor hemorghaging
Astrigent
infiltrating with local anesthetic to adjacent gingival papillae
what is the paste made of
Aluminum chloride
how is the paste placed
Injected into the dry sulcus with a special gun
pros and cons of paste
Pro: less disscomfort and good hemostasis
con: less tissue displacment, die trimming more difficult
what is electrosurgery
Removing the inner epithelail lininig of the gingival sulcus
uses high current to cause cell death, and ultimitely cuts the gingiva
can you use irreveresible hydrocolloid for cast restorations
No, not sufficiently accurate
benifit of Polyethers and addition silcones
Sufficient long term dimensional stability
what can not be poured in reversible hydrocolloid
epoxy or electroplated
need to be poured emiadly
Pros of reversible hydrcolloid
excellend dimenstional accuracy acceptable surface detail hydrophilic ( good for moisture problems) long working time good cost no custom tray
cons of reversible hydrocolloid
pour immediately
changes from gel to sol at high temp
low tear resitsance
lack dimenstional stabilisy
what is needed to do a reversible hydrocolloid impression
water cooled impression trays
types of reversible hydrocolloids
heavy body tray
viscous syringe material
how to help with dimensional changes in reversible hydrocolloids
thick as possible to increase volume to surface area
Pros of polysulfides
high tear strength
easier to pour that others
cons of polysulfides
messy
unpleasant odor
long setting time
stains clothes brown due to lead
when should polysulfides be poured
right after impression despite better dimensional stability
what tray is used with polysulfides and why
Custom to minimize bulk therefore reducing contraction
pros of condension silicone
pleasant to use
short setting
cons of condension silicone
hydrophobic
Poor wetting
low stability
what was deveoped to overcome polysulfide disadvantages
Condensation silicone
do patients prefer condensation silicone or polysulfides
Condensastion silicone due to its short time
how to take a condesation silicone impression
heavy filled putted material to customize stock impression try
thin wash of light bodied is squirted in to make impresssion
pros of polyethers
dimension stability (no volitle product produced Accuracy automix available lasts a long time
cons of polysethers
set material very stiff- can break casts
imbition
short working time
allergies
how does polyether set
Using a polymerization reaction
pros of Addition silicone
Dimensional stability Pleasantto use Short setting time Automix Avaible less ridged thanpolyether and stiffer than polysulfide
Cons of Addition silicone
Hydrophobic
Poor setting
some materials release H2
Hydrophilic formulation imbibe moisture
other name for addiition silicone
Poly(vinyl Siloxane)
benifit of adidition silicone over condensation silicone
Much better dimensional stability
when not to use spray on adhesoin for trays
Polyvinylsilozane
benfit of a custom tray
good for elastomeric impresion by limiting volume of material
- reduce stress during removal and thermal contract
why don’t use a custom tray in hydrocoloids
dimensional change by water loss so you want bulk
how thick should custom trays be to get ridigd
2-3 mm
what do you need for doing elastomeric material impressions
Assistant or auto mix technique
what to do with displacment cord when doing an impression
remove right before placing th etray
what todo with light body
squirt it all over the prep at the distal but keep as thin as possible cuz it shrinks more than heavy body
what is the automix tequire
the squirter thing we use in class
when is a triple tray used
popular for making impressions for single unit and less expensive restorations made to conform to the existing occlusion
what is done to make a tripple tray
maximum intercuspation
high viscosity polyether or polyvinvylsiloxane supported by a thin mesh frame
what is the definitive cast
the master or working cast that is the replica of the preped teeth, ridge areas, and other parts of the dental arch
what is the die
positive reprodcution of the preped tooth of suitable hard substance with correct accuracy
can a cast and die contain more info than the impression
No
what are two important qualties of cast and die materials
dimensional accuracy and reistance to abrasion while wax pattern is formed
what makes different kinds of dental stone different
Different levels of calcification
what should you do if you need to soak gypsum
soak in water saturated with gypsum as to not dimminish surface detail
why use resin to make a die
To increase the low strength and abrasion resistance of die stone
how does electroplatting work
Coat of pure silver or copper on impression then filled with stone
why use flexible die materials
Interum restorations
what are the 2 pours for a die
1 to form the tooth
2nd to form the base
how are diagnostic casts best mounted
In cr
how should definitive casts be made
At Maximum intercuspation of unpreped teeth
why do reorganize occlusion
If there is some pathological problem with occlusion to begin with and will the patient benifit
why do Conformative occlusion
To maintain current occlusion patterns even if it is not the correct occlusion pattern
when to do conformative occlusion
when patient has only 1 or 2 crowns
how should the intended metal-ceramic junction look
should be as definite(90 degrees) as possible and smooth
how to remove investment for a MCC
using an airborn particle abrasion or steam
how to remove the oxide layer from MCC
acid or air abraishioin
why thin the margin to a knife edge
make sure margin isn’t visible
what is made on the metal layer for creating the bond between metal and porcelain
oxide layer for the chemical bond by using a firing tray
what is dental porcelain made from
Quartz
Feldspar
other oxides
what does body porcelain do
Translucency and oxides that aid in shade matching
