Dental Handpieces Flashcards Preview

Semester II - Dental Materials > Dental Handpieces > Flashcards

Flashcards in Dental Handpieces Deck (24)
Loading flashcards...

What are the two types of dental handpieces available to prepare teeth?

1. High Speed

2. Speed-increasing


What are the features of a High Speed handpiece?

1. Also called air-rotor or air-turbine

2. Driven by a supply of compressed air (pressure is usually 3 bar/43.5 psi)

3. Uses Friction Grip (FG) Burs


Why should you ensure the Bur is fully engaged?

- Can cause intraoral soft tissue injury or be lost into the patient's oropharynx

- Any eccentricity in running of the chuck is exaggerated and it may cause damage to the chuck and bur


High-Speed Bur: What can happen if the bur fails to run centrally?

Bur judder:
- Leads to vibrations that then transmit to material; causing cracking and crazing
- Unpleasant vibrations for the patients

Eccentric cutting:
- Results in irregular removal of tissue being prepared so more tissue is removed


What's the important of water cooling with High-Speed handpieces?

- Friction heat is generated; water cools it down

- Heat can have detrimental effects on dental pulp

- Improves your vision; clears debris from the area you're working on


What's the importance of Torque?

Torque = Torque is the twisting force that tends to cause rotation

Torque decreases linearly as rotational speed increases

i.e. the bur requires more power to continue to rotate it at the same speed as the pressure applied to it increases - due to the increasing drag on the bur


What happens to the rpm of the high speed turbine when applied to tooth/restoration?

- Free running speed is around 3-400,000 rpm

When applied to the substrate it can drop to 180-200,000 rpm


How can the air supply effect the power in High-Speed Handpieces?

- A problem with air supply can cause fluxuations in the air pressure (not good) = fluctuating speed and torque


What are the uses of the High-Speed handpiece?

- Cutting of enamel and dentine

- Removal of direct restorative materials

- Tooth preparation for indirect prostheses

- Gross shaping and polishing of cured direct restorative materials

- Removal of indirect prostheses

- Sectioning of teeth


What's are some of the features of a Speed-Increasing Handpiece?

- Driven by an electric motor

- Smoother and more precise cutting compared to high speed

- Less noise and vibrations

- Uses latch grip burs


How does the speed and torque differ with the speed-increasing handpiece?

- The bur rotates at a constant speed and torque


How is consistent power and thus torque maintained?

- Via the electric motor - keeps consistent features when the bur contacts the tooth


What;s the mode of cutting with a speed-increasing handpiece?

- Rotates

- Ideal when doing work that requires a smoother running bur and precision such as:
+ Refining tooth prep
+ Tooth hemisections
+ Polishing


What's a slow-speed handpiece?

- Speed range between 600-40,000 rpm


How does the slow-speed handpiece work?

- The same as the speed-increasing handpiece

- Internal gearings are different and the latches used


What is the slow-speed handpiece used for?

- Removal of dental caries
- Polishing enamel and restorative materials intraorally

- Oral surgery
- Extraoral adjustments


What's the recommended cutting speed (rpm) for Cavity Preparation?

230,000 prm

- High-Speed or Speed increasing


What's the recommended cutting speed (rpm) for Caries Removal?

1500-20,000 rpm

- Low speed or speed-decreasing


What's the recommended cutting speed (rpm) for Fine finishing and Polishing?

20-40,000 rpm

- Low-speed or speed-decreasing


Whats a Diamond bur?

- Consists of a central shaft of metal forming shank

- Resin added onto this into which fine diamond particles are embedded

- Various layers of diamonds are slowly revealed as the bur wears due to plucking out of diamond particles

- Sometime they're multilayered


Abrasivity: How can diamond burs vary in coarseness?

- Use depends on the bur's abrasivity and this is determined by the size of diamond particles embedded in resin

- Varies from Supercoarse to ultrafine


What are the colour codes for diamond burs?

- Supercoarse
- Removal of existing restorations
- Size of particle = +175μm

- Coarse
- General tooth prep
- Size of particle = 150-175μm

- Medium
-Removal of existing restorations
- Size of particle = 105-125μm

- Fine
- Refining and finishing
- Size of particle = 45μm

- Super/extra fine
- Finishing
- Size of particle = 25-30μm

- Ultrafine
- Finishing
- Size of particle = 15μm


What are Tungsten Carbide Burs?

- Alternative to diamond burs

- Very brittle

- Bur "snatches" substrate via grind and chip the surface = CLEANER than diamond


How are Tungsten Carbide burs produced?

- They are milled to produce the cutting tool which allows for specific bland angles