Dental Handpieces Flashcards
What are the two types of dental handpieces available to prepare teeth?
- High Speed
2. Speed-increasing
What are the features of a High Speed handpiece?
- Also called air-rotor or air-turbine
- Driven by a supply of compressed air (pressure is usually 3 bar/43.5 psi)
- 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
