Flashcards in Fixed - L1 - Margin & Burs Deck (37)
Conventional diamond burs are made by ...?
...plating small industrial mineral diamond particles on stainless steel shanks by a galvanic process
What are limitations of diamond burs?
1. heterogeneity of grain shapes (irregular)
2. difficulty of automation
3. short lifetime
Why do diamond burs have short lifetimes?
1. repeated sterilization (loss of particles)
2. ultrasonic cleaning solns w/ pH greater than 11 corrodes the nickel matrix (loss of particles)
3. potential smearing of Nickel ions from metallic binder onto the dental substrate
What are the types of bur designs?
3. modified-(round, flat)-end)
4. end cutting
Per ISO standards, the diameter of a rotary instrument is defined as the...?
widest part of the cutting surface
Objective of restorative therapy...?
to protect dentin, pulp, and other structures
Damages during tooth prep could occur to...?
adjacent teeth, soft tissues, and dental pulp
- we are more concerned w/ mechanical dmg to pulp
Increase in frictionally generated heat is influenced by...?
2. duration of applied force (intermittence)
3. condition of burs
4. rotational speed
5. use of coolant!
6. remaining dentin thickness
what is the adequate force for the burs?
1-4oz of force
What condition should the burs be in?
use NEW burs consistently
What should the rotational speed of the HS handpiece be?
What should the remaining dentin thickness be?
2mm ideal, 0.5mm increases risk of toxic injury by 25%
3 - 25% of teeth develop _____ as a result of tooth prep for CCC.
Whenever possible, margin should always be placed _____.
Exceptions to placing margin supragingivally?
1. cervical erosion (sensitivity)
2. subgingival restorations
3. prox. contact extends to the gingiva
4. additional retention & resistance is needed
5. surveyed FDP where undercuts are planned for clasp retention
What are the types of margin designs?
chamfer, shoulder, feather edge beveled shoulder
*we only use the first 2
- last one is most conservative
What is CVD?
Chemical vapor deposition (CVD); technique most modern/urban companies are using to help form a more even and uniform grain shapes in diamond burs.
what happens when you lose the diamond particles on the tip of the bur?
bur will create more heat
what are the 5 variables of bur design?
1. TYPE (shape)
2. LENGTH (total & cutting)
3. SIZE (HEAD/(Ø)
4. GRIT (texture)
which variable of bur design is most important?
what are the most common types of burs for fixed?
parallel and tapered burs
goal of using burs in fixed?
to generate the most type of cuts w/ the lease amt of burs
what does grit depend on?
the size of the diamond particles
Color for the burs & Grit type:
gray - ?
white - ?
green - ?
red - ?
black - ?
yellow - ?
white - ultra fine
yellow - super fine
red - fine
gray - medium
green - coarse
black - super coarse
range of length for bur design? (include total & cutting)
total: 14.5 - 25mm
cutting: 0.08 - 10mm
range of size (head/(Ø)?
0.5 - 8.0mm
range of grit for bur design?
Ultra fine (8μ) to Super Coarse (150μ)
type of handpiece for fixed burs?
FG, Latch, Straight, Stryker
what type of bur makes it easier to avoid J-margins?
modified round-end taper