Burs - Background Info Flashcards
rotary cutting instruments consist of a ____ and the _____/_____
handpiece
Bur/abrasive
The handpiece provides the ___
rotational energy
The bur/abrasive makes contact with and____ or ____ the tooth
Cuts
Abrades
Straight handpiece
Long axis of bur = long axis of handpiece Always low speed Long burs - HP Friction grip chuck Rarely used intraorally
HA burs
Long friction grip burs for use in the straight handpiece
Contra-angle handpiece
Long axis of bur about 115 degrees from long axis of handpiece by two bends in the rotational shaft
Low speed handpieces operate up to _____ rpm
8k-35k rpm
High speed handpieces operate up to ____ rpm
160k - 500k rpm
Why do high speed handpieces require water coolant spray?
Produces a lot of heat that can damage tooth tissue and pulp
High speed handpieces are used for…
gross reduction
High speed handpieces are involved in ___% of the cavity prep
90%
Low speed handpieces are used for…
Cavity refinement and restoration finishing and polishing
Bc they provide greater tactile feedback to DDS
Slow speed contra-angle handpiece
friction grip or latch head
LA/RA - latch burs - wider shank
FG - friction grip burs
LA/RA burs
latch burs to be used in the slow speed contra-angle handpiece
wider shank diameter than friction grip burs
FG burs
friction grip burs to be used in the slow speed contra-angle handpiece
High speed handpieces are always ______ and have _______ chucks
contra-angled
friction grip
Carbide burs
Head made of tungsten carbide - very hard, still sharp at high temps
Neck/shank - nickel plated steel
Round burs
We have 4 carbide FG round burs
Used for various aspects of cavity prep
Low or high speed
“Caries removal burs”
WE DON’T HAVE THESE
LA round burs
Used for removing soft, leathery dentin in caries lesion
Fissure burs
6 bladed carbide FG burs
Long, slender profile
Used for extending prep into occlusal pits and fissures
Straight or Tapered
Plain straight fissure bur
creates sharp internal line angles
Plain rounded fissure burs
Creates internal anatomy with rounded line angles
Crosscut burs
Additional set of cuts across each blade Increase cutting efficiency Comb-like appearance More agressive Less chatter
At high speeds there is _____ difference between burs with and without crosscuts
little
Tapered fissure burs
Sides are convergent
Sides tapered 2-4 degrees off vertical axis
Used for cast gold preps where cavity wall taper is desireable
Finishing burs
12 bladed FB burs
Less aggressive at cutting than the 6 bladed carbides but have smoother finish
Low speed - finishing restorations
Abrasives designed for use with rotary instrumentation are generally designed for use with the ______ handpiece
Low speed
Mounted stones
WE HAVE 3
Green carrot stone - coarse
Green sphere stone - coarse
White carrot stone (Arkansas stone) - medium
Used for early stages of finishing metallic restorations
FG or LA
Mounted stones should NEVER be used on…
composite resin restorations
Impregnated rubber points
Carrot shaped FG shanks Brownie - coarser Greenie - less abrasive Used for fine finishing and polishing of metallic restorations
Impregnated rubber points shoud NEVER be used on _____
composite resin restorations
Light colored LA rubber abrasives
Enhance - fine
PoGo - superfine
Used for composite resin finishing and polishing
Various shapes
What are the 2 styles of mandrel
- Moore’s - snap - square hole
2. Soflex/pop-on - round hole
a dull bur results in a ______ prep
oversized
This is due to the DDS needing to use extra force to get bur to cut
Control and tactile feedback greatly diminished
A dull bur can damage the underlying pulp through ____
generation of excessive heat
How can you identify a dull bur?
Visual inspection doesn’t work
Behavior under function
Signs that a bur might be dull:
- Burns, chars, darkens tooth
- Chatters/vibrates rapidly
- Requires pushing to get it to ‘bite’ into tooth
- Anytime bur seems sluggish/reluctant to cut, it may be dull
When evaluating if a bur is dull, is it critical that the handpiece is functioning at _____ and _______
optimum speed
in the forward direction of rotation
