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What are the three file types?
- 1.Carbon steel
- 2. Stainless steel
- 3. Nicket titanium (what we use today)
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What is the taper of a nickel titanium rotary instrument?
- For every mm, you increase .02mm
- There is a .04 taper and a .06 taper
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Which hand and rotary instruments are lathe ground or machined?
Hedstrom, most nickel titanium, and some K-files
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How are hand/rotary instruments ground and twisted?
- Ground into square, triangular, or rhomboid blanks
- Twisted counterclockwise to produce helical cutting edges
- Have a pyramidal tip of 75 degrees or -15 after twisting that is rounded and non-cutting
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Which has more twists/mm, reamers or files?
Files have more twists/mm
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How far do cutting flutes extend up to the tip of the file?
16mm (Do-D16)
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What is the change in tip sizes?
- Tip size increases by .05mm up to size #60
- Tip size increase .10mm from #60-140
- File diameter increases .02mm/mm of length (Do-D16=.32mm)
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What are the tapers on Nickel titanium instruments?
.02, .04, .06, .08, .10
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Between which two file sizes is there the largest increase?
between 10-15
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Which files are hand operated?
- K-type files and reamers
- Barbed broaches
- hedstrom files
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Which files and reamers are engine driven?
- Files and reamers (constant counterclockwise rotary motion
- Files and reamers (reciporocates 90-180 degrees each way)
- Gates Glidden- (#2,3,4)
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What are some aspects of carbon steel files vs. stainless steel?
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What is the torsional limit?
Amount of rotational torque that can be applied to a 'locked' instrument to the point of breakage
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Which instruments have higher torsional limits?
- Smaller instruments (<20) withstand more rotations than larger
- Machined files deform more quickly
- Nickel titanium files have increased resistance to fracture compared to stainless steel
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How do you avoid separation, unwinding, and roll-up?
- Inspect instruments before each use
- unwinding results from clockwise twisting
- Roll-up results from counter-clockwise twisting
- Instruments separate more easily in a counter-clockwise direction
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Nickel titanium rotary instruments
- 50/50 combination of Nickel and Titanium
- Very corrosion resistant
- Superelastic, has shape memory
- Has two reversible configurations (austenite and martensite)
- More resistant to fracture than stainless steel and more difficult to pre-bend
- Usually made by micromachining
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What are some features of the X-smart endo motor?
- Speed and torque control
- Auto-reverse
- Able to program settings
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What RPM are Gates Glidden files set at?
800 RPM
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What RPM are numbered files set at?
300 RPM
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What does sterilization do?
- Unlike disinfection, sterilization kills all organismsThey can't eliminate Prions
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What are the two types of sterilization?
- 1. Pressure (steam and chemclave)
- 2. Dry heat
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What are the settings for Steam sterilization?
121 degrees Celcius and 20 psi for 30 minutes
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What are the operations for Chemclave?
- Causes less rusting of steel instruments than steam
- Uses alcohols, ketones, formaldehyde, and water
- 127 degrees Celcius and 20 psi for 20 minutes
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Which dulls cutting edges faster, Pressure or Dry heat?
Pressure dulls cutting edges faster
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What are the types of disinfectants?
- Mostly phenolic
- 70% isopropyl alcohol
- Quarternary ammonium solutions
- Sodium hypochlorite 5.25% to 6%
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What are the irrigants used today for canals?
- NaOCl- Kills bacteria and dissolves necrotic tissueEDTA- Kills bacteria and removes smear layer
- Chlorhexidine- Kills bacteria with no tissue dissolutionDistilled water- only flushing and debris removal
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Action of sodium hypochlorite
- Sodium hypochlorite 5% at 50 degrees C
- Should be left in canals for a minimum of 10 minutes during treatment
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Calcium hydroxide
- High pH (11-12)
- Reduces bacterial colonization except enterococcus and actinomycesCan dissolve necrotic tissue
- Reduces toxic by-products
- Placed by counter-rotated files, lentulo spirals or compaction of dry CaOH poweder
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What is the smear layer?
- 1.Fragments of microscopic mineral crystals produced by instrumentation
- 2.Organic debris
- 3. Bacteria and by-products, viruses, fungi, yeasts
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Why do we want to remove smear layer?
- Source of substrate for bacterial growth
- Avenue for leakage
- may prevent or delay disinfectant action
- may interfere with sealer or gutta percha adhesion
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How is the smear layer removed?
- Organic and inorganic acids
- EDTA, RC Prep, 5-10% Citric acid
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