JVD 2019 #3 Foundations- The Air-Driven Dental Unit: Form and Function at a Mechanical Level; Pegg Flashcards
Two types of compressors?
Small compressor driving single dental unit on a mobile cart
Large compressor remotely with hose to dental unit (less noise, less operative space, can run multiple machines, higher initial cost)
Compressed nitrogen- (tanks located remotely, less noise, need to be filled/delivered/monitored)
How does a compressor work?
Using an electric motor, takes room air at atm pressure and compresses it into a high pressure storage tank. Store at higher pressure than needed- ie 80 PSI when handpieces operate at 40 PSI.
What does the pressure regulator do?
High pressure storage tank (ie 80 PSI) -higher pressure than needed when handpieces operate at 40 PSI. This decreases pressure to handpieces. If only maintained at needed level, the pressure would dissipate during use and reduce speed/power
What is the rehostat?
Foot pedal used to activate the handpiece
* high speed always meant to be used at full speed for cutting burs! Some finishing burs and slow speed attachments can use varying speeds.
Low speed handpiece
single piece or combo of 2 parts
Most riven by a rotary vane motor
Full rotary cycle repeated 20-40K x/min
Forward or reverse direction alternating air inlet/outlet
Air motor rotates, turns a drive shaft connected to turn a gear train–> mech adv gearing down rotation of air motor provides more torque to final drive shaft to provide rotation
Colored rings of the micromotor low speed handpiece
Indicate internal gear ratio
No color or blue= attachment turns at same speed as motor drive shaft
Green= reduce gear ratio 4:1 (ie speed of attachment is 4x slower than rotation of motor (motor 20K rpm then attachment is 5K RPM)
Red= speed increasing handpiece 1:5 (20K motor RPM= 100K attachment RPM)
HIgh speed handpiece
350-400K RPM, decreased when working against friction
No gear ratios or different attachments (single speed)
Very low torque relies on RPM to be effective
Turbine can only rotate one direction
Air exhausts down handpiece back to motor
Water cooling component= additional air “chip air” used to atomize water at head of handpiece to create fine mist
+/- light- fiber optic vs bulb
What is a turbine?
Device that rotates as air flows across its blades or vanes.
Can only rotate 1 direction
Used in High speed handpiece
What are the 4 holes in a standard high speed connector?
What others do the 5 hole and 6 hole connectors have?
- 2 large holes (air) smaller supplies drive air to instrument (needs lubricant), larger takes exhaust air back to unit
- 2 smaller holes provide chip air and waterflow for cooling
- 5th hole= fiber optic/light
- 6 hole= 1 for electric and 1 for light bulb
How is the Venturi effect used to create suction for the dental unit?
Generates a partial vacuum using high speed compressed air exhausted through a narrow aperture creating negative pressure
