Fixed Q4 Flashcards
What is worse, an open margin or an over-contoured crown?
Over contoured
plaque trapped underneath
What is the most critical and neglected aspect of occlusion?
Lateral excursive movements
Most errors in crown contours are found where?
Embrasure spaces
If crown is deficient, how would you add matl IP or occlusally?
Ceramic - stack low fusing porcelain
Metal - solder
What type of luting material needs anesthesia?
What type strengthens restorative material?
Bonded Resins
for both
What is the advantage to a Luted crown?
What is the disadvantage of a Bonded crown?
sectioned and removed easily
prepped off
What type of cement will increase the flexural strength of glass ceramic crowns?
Adhesively bonded resin
T/F
You can bond zirconia and metal
False
*crystal/metal won’t adhere to bonding agent
For emax, would you lute or bond if you lacked resistance form?
bond
For emax, if you can’t isolate, would you lute or bond?
lute
*adhesive cement very difficult if can’t isolate
T/F
Bonding strengthens, holds over time better but if you have retention/resistance you often don’t need it
True
T/F
Bonding is very difficult to remove and more technical to apply
True
Name 3 advantages to luting with RMGI:
postcementation sensitivity minimal
higher strength than normal GI
strength similar to resin luting agents (but not really)
Zinc Phosphate has a film thickness of ___ um, is easy to clean, and has a long track record of success
25
What has better biocompatibility than Zinc Phosphate b/c polyacrylic acid molecule is large and does not penetrate into the dentinal tubules?
Zinc Polycarboxylate
What luting agent is superior to Zinc Phosphate and Zinc Plycarboxylate and is susceptible to moisture?
GI
What luting agent is extremely biocompatible but has mechanical properties inferior to other cements?
Zinc Oxide Eugenol
Why are resin cements susceptible to incomplete seating?
High film thickness
2 goals of provisional cements?
seal margin
prevent leakage/pulpal irritation
What type of provisional cement does ASDOH use?
tempbond NE - zinc oxide bases cement
*NE stands for Non-Eugenol
Why is Eugenol bad in resins?
free radical scavenger that can inhibit resin setting
Normal Provisional cement we use is tempbond NE, what is the stronger one we use?
What type of cement is it?
Durelon
Polycarboxylate
Sequence of check when seating a crown:
IP
Margins
Occlusal
Contour
Esthetics
If crown isn’t seated all the way and you adjust the occlusal contacts, you will be in…
Hypo-occlusion
Check IP contact with…
accufilm
A removeable die system is set in Type ___ gypsum, and it can abrade the IP contacts so adjustments are made on another poured up non-removeable system
IV
You can’t get an explorer in all IP contacts, so what to do?
If you don’t have adjacent teeth, do you still need to take a radiograph?
Radiograph
NO - not if detectable with an explorer
How thick is accufilm?
21 microns - fold over technique to see how much to grind (by measuring adjacent teeth to the one in hyperocclusion)
Sequence to bond a veneer:
Veneer
HF
Silane
Bonding (No primer)
luting
Bonding (w/ primer)
HPO4
Veneer prep
What is the purpose of a primer?
Why don’t use on veneer?
Hydrophilic to hydrophobic
no dentin - no need
We can’t use adhesive bonding if the Intaglio is…
Metal or Crystal
*so no zirconia, no PFM
Would we lute or bond empress?
Bond
-will increase strength
Would we lute or bond emax?
Either
- if min. occlusal thickness bond
- if good retention/resistance lute
Why do we add grooves and boxes to a gold crown prep?
Irregularities help luting agent - and prevents leakage
Brand name of the RMGI we use to lute in clinic:
FujiCEM
- increases strength, lowers solubility
- RMGI is still considered luting
In an endo tooth - If 3 or more walls have a 1mm thickness following crown prep, do what?
Chamber retained core buildup
When should a post be used in an endo tooth?
Retention inadequate
*two walls or less
To put Amalgam in a core buildup, how thick should the wall be after a prep is made?
1 mm
What type of build up is used for multi-rooted teeth that have gone through endo?
Chamber retained core build up
*has dentin thickness and pulp chamber adequate
The height of a core build up has to be at least what?
4 mm
*either height of pulp chamber or into root canal
As a core material composite has a _____ CTE
____ modulus of elasticity
Bonding to denting that is _____
high
low
not strong
What is the disadvantage of GI as a core material?
Strength
*also moisture sensitive and low tensile strength
What is the purpose of a Post?
What does it NOT do?
retain core build up
reinforce tooth
A post should only be considered to retain core build up when?
all other forms of retention are inadequate
*only two walls
A post is ideally ____ the length of the root
An apical seal of at least ___mm of GP is to remain
2/3
4mm
What is more important, 4mm of GP remaining when placing post or it being 2/3 of the length of root?
4mm
Post diameter should be limited to ____ the root diameter
1/3
T/F
Strength of an endo treated tooth is directly related to bulk of dentin structure
True
What type of post leads to higher fracture rates?
Active
*screwed in
What type of Post has enhanced esthetics, excellent biocompatibility, mechanical properties similar to dentin, easy to use/remove, firm retention with adhesive, and lower radiopacity than a metal post?
Fiber reinforced
Two types of Posts:
Fiber and Metal
How is a Metal post placed?
Fiber?
Luted
Bonded
What type of Post is one piece, high cost, and technique sensitive?
Cast
How big should a ferrule be?
2-3mm
What is the function of a ferrule?
reduces tooth fracture
Mechanical loading will produce cracks that progress in what direction?
Coronal to Apical
Fatigue failure is more catastrophic in what type of tooth?
Nonvital
*complete root fracture may occur
Libman Nichols found that Ferrule length worked better at 1.5mm than 2mm - why?
2mm had to cut tooth structure down, lowering C/R ratio
Ideal Crown to Root ratio:
Minimum:
2: 3
1: 1
If we have less than 1:1 Crown to Root ratio, what type of occlusal trauma will ensue?
Secondary - reduced peridontium
In upper anterior teeth, what wall is the most critical in reducing load fracture?
Palatal
We want how many mm of Ferrule above the margin?
2mm
T/F
Ferrule effect is for resistance/retention
False
*designed to prevent tooth splitting
2 techniques to gain adequate tooth structure:
Crown lengthening
Orthodontic extrusion
Crown to Root ratio better with extrusion and crown lengtheing
Yes?
Junctional Epithelium + Connective Tissue
Biologic Width
On average we want __ mm from the bone to where the core material starts
5
*2 bio width +1 sulcus +2 Ferrule
One article concluded that a post doesn’t strengthen a tooth, but weakens it
True
Do you have to crown a tooth that has been endo treated?
No
Endo Tx teeth last how long?
1-25 years
Sorensen et al concluded that _____ didn’t significantly improve that rate of clinical success for Mx and Mb teeth
Coronal coverage of anterior teeth
Sorenson et al concluded that intracoronal reinforcement (a post) didn’t do what?
increase resistance to fracture
The purpose of a post:
Retain core build up
Bridge, aka
FPD - fixed partial denture
FPD, dummy tooth:
Crowns:
Crown prep:
between dummy tooth and crowns:
Pontic
Retainer
Abutment
connector
Ante said that the combined pericemental area (root structure) should be greater than or equal to the area of the teeth being replaced
True
*all root area
Does an FPD have to fulfill Ante’s Law?
No
- most don’t and are fine
- now it’s more like Ante’s Guideline
an FPD only one side of which is attached to a retainer
Cantilever
Why is a Cantilever not ideal?
Doesn’t direct forces along long axis of the tooth
*why generally don’t do and recommend implants instead
Greatest failure rate in Sorensen study was pulpless (endo Tx) teeth with?
No crown
3 reasons a tooth needs a crown:
Tooth structure
Improve esthetics
change contours
A crown that supports a removable partial denture (RPD)
Survey Crown
RPD abutments fail 2x as often as FPD
True
A Post will decrease the success rate of an FPD
True
What tooth should be prepped 1st in FPD?
Smaller
premolar rather than molar - errors can be corrected w/ greater tooth structure
What instrument can detect undercuts when prepping an FPD?
Surveyor Instrument
*also CEREC
