Operative and endo Flashcards
What is a crown?
A restoration that encompasses coronal tooth tissue, covering remaining tooth substance and restorations
Why do we place crowns?
What pressure is exerted when cutting at low speed?
2-5 lb
n.b. speed is inversely proportional to the pressure
What pressur eis exerted when cutting at higher speed?
1 lb
n.b. speed is inversely proportional to the pressure
What pressure is exerted when cutting at ultra high speed?
1-4 oz
What increases heat production of a treatment?
RPM of instrument
Amount of pressure applied by operator
Area of tooth in contact with the tool
What happens to the pulp at 113 degrees F?
Inflammatory respinse of pulp = Pulpitis
(n.b. this is reversible)
What happens to the pulp at 130 degrees F?
Permanent damage to the pulp
= pulpal necrosis
What are the uses of rotary cutting instruments?
- Intra-coronal tooth preparation
- Excavation of caries
- Finishing cavity walls
- Finishing restorations
- Polishing restorations
- Removing old restorations
- Extra-coronal tooth preparation
- Separating crowns and bridges
- Adjusting acrylic prostheses
What are the 2 different designs of low speed handpieces?
Straight/contrangle
What is the speed range for a slow handpiece?
10,000 to 30,000 rpm
Which direction do slow handpieces turn?
Either clockwise (forward) or anticlockwise (backward)
What are the clinical uses for slow handpieces (5)?
- Cleaning teeth
- Caries excavation
- Finishing and polishing procedures
- Adjustment of porcelein
- Root canal treatment
What are the lab uses for slow handpiece?
Trimming and adjusting of:
Temp crowns
Removable prostheses
Orthodontic appliances
What are the (2) advantages of low speed handpieces?
Better tactile sensation
Less chance of overheating cut surface
What are the (7) disadvantages of low speed handpieces?
- Ineffective compared to high speed
- Time consuming
- Need to apply more pressure
- Vibrations (uncomfortable for patient)
- Slower cavity prep (increased operator fatigue)
- Burs have tendency to roll out of preperation
- Carbide burs = brittle = break at slow speed
What are the uses of high speed handpieces?
Tooth prep & removal of old restorations
What are the (3) advanatges of high speed handpieces?
- Faster
- Less pressure, vibration and heat needed
- Less operator fatigue
What are the (3) disadvantages of fast handpieces?
- Increased temp (without water)
- Less tactile sense (overcutting possible due to water spray)
- Air & water spray impair visibility
What speed do high speed handpieces go?
450,000 to 500,000 rpm
What are the 3 basic parts of rotary instruments?
Shank = fits into handpiece (friction grip/ latch grip)
Neck = connects shank to head
Head - cuts/finishes/polishes
Where do you dispose of fractured/blunt burs?
Sharps bin
What happens to caries hen it reaches the enamel-dentine junction (EDJ)?
Why?
It spreads laterally and deep into dentine
This is because….
Dentine has a lower inorganice mineral content than enamel = softer
In a carious lesion that extends up to half way between the EDJ and the pulp will the superficial dentine caries be hard or soft?
Soft
it will also correspond to the zone of destruction (bacterial invasion) histologically




