Handpieces in Operative Dentistry

The removal and shaping of both diseased and sound tooth structure is an essential part of restorative dentistry.

Initially this was a difficult process accomplished entirely by the use of hand instruments, bulky chisels and excavators

The introduction of rotary, powered cutting equipment was one of the truly major advances in dentistry

The term ‘rotary instruments’ in dentistry refers to a group of instruments that turn on an axis to perform a work such as cutting, abrading, burnishing, finishing or polishing tooth tissues or a restoration.

A handpiece in Operative dentistry is a device for holding rotating instruments, transmitting power to them and for positioning them intra orally. Dental handpiece of today is a sophisticated combination of precision parts moving in perfect synchronization at extremely high speed.

History of Dental Handpieces

Classification of Handpieces

According to driving mechanism-

Gear driven hand piece
Water driven hand piece
Belt driven hand piece
Air driven hand piece
Electric driven (Recent)

Depending upon angulations-

Straight
Contra angled
Right angled

Depending on speed

Sturdevant classification:

Low or slow speeds (less than 12,000rpm)
Medium or intermediate speeds (12,000 – 20,000 rpm)
High or ultra high speeds (more than 200,000 rpm)

Marzouk classification

Ultra low speed - 300 -3000 rpm
Low or slow speed- 3000 -6000 rpm
Medium or intermediate speed - 20,000 – 45,000 rpm
High speed- 45,000 – 1,00,000 rpm
Ultra high speed – more than 1,00,000 rpm

Based on head design

Standard
Mini
Torque

Based on bur holding type

Screw type chuck
Airmatic bur changer
Ultrapush system

Based on motor

AIR TURBINE
AIR MOTOR

Based on colour coding ring

Blue–no change in speed
Green-speed reduction
Red –speed increase

Handpieces used in endodontic

Giromatic hand pieces
Reciprocating hand pieces
Sonic and ultra sonic hand pieces
Torque control gear reduction hand pieces

1. According To Driven Mechanism

Gear Driven Handpieces

Rotary power is transferred by a belt which runs from an electric engine.

Power is transfered from the straight handpiece by a shaft and gears inside the angle section.

Capable of working at variable speeds though they work best at low speeds because of so many moving parts with metal to metal contact

Water Driven Handpieces

Water Driven Handpiece

In 1955, a hydraulic driven turbine handpiece was reported to operate satisfactorily at 60,000 rpm.

Two years later the first commercial model called a Turbojet became available.

Improved units have both straight and angle handpieces which will operate at speeds upto 100,000 rpm

Water is conveyed to and from the handpiece by a co-axial type tubing (tube inside a tube)

The small inner tube carries water under high pressure to rotate a turbine in the handpiece head and the larger outer tube returns the water to the reservoir. From here it is recirculated over and over.

The handpiece is extremely quiet and has the highest torque.

Belt Driven Handpieces

Belt Driven Handpiece

A belt driven angle handpiece called the Page-Chayes became available in 1955 and was the first angle handpiece to operate successfully at speeds above 100,000 rpm.

All gears were eliminated by having a small belt run inside the handpiece sheath over ball bearing pulleys in the angle sections.

Improved models of the belt driven design are the Page-Chayes 909 and the Twin 909.

They have a history of excellent performance and great versatility and free of maintenance.

Air Driven Handpieces

Air Driven Handpiece

In the latter part of 1957, the first clinically successful air driven turbine handpiece became available with free running speeds of approximately 300,000 rpm.

The air is directed to the head of the handpiece and is blown against the blades of a small turbine to produce rotation while the greater part is exhausted at the back of the handpiece or returned to the control box.

1973 – The first high-speed handpiece with fiber optic illumination is introduced.

Provide the operator a source of artificial illumination through the dental hand piece.
Transmission of light through long, thin fibers of glass or transparent material.
Each individual fiber is approximately 25 microns in diameter.
The light travels, non-electrically, through the fiber by reflecting from wall to wall without transmitting or generating heat. This makes fiber optics completely safe for use in the oral cavity

Fiber Optic Handpieces

Parts of Handpieces

The air driven mechanism works on two principles

Rotary vane principle
Swash plate principle

Electric Driven Handpieces

Electric Driven Handpieces

Most are direct current motors and are designed with an armature sitting within a permanent magnet assembly the performance depends upon

Design and power of the magnetic field
Design and number of armature coils
By varying the distance from the magnets to the rotating armature, the speed of the motor can be altered.

The biggest difference in comparing an electric handpiece to an air driven is its constant speed and less noise.

HYBRID AIR-ELECTRIC HAND PIECE ( ATC)

ATC refers to Adaptive Torque Control
This system resembles an electric installation but is referred to as a hybrid, using both air pressure and electricity.
Uses a sensor in the hand-piece tubing to operate a valve that continuously regulates the amount of air pressure flowing to the turbine.
Instead of the hand-piece losing power and free running speed – when the bur contacts the tooth, the valve opens , sending more pressure to the turbine to compensate.

2. According To Angulation

Straight Handpiece

long axis of bur lies in same plane as long axis of handpiece.
Can be attached to micromotor or airmotor.
It is used in oral surgical and laboratory procedures

Contra-angle Handpiece

Head of handpiece is first angled away from and then back towards the long axis of the handle.
Because of this design, bur head lies close to long axis of the handle of handpiece which improve accessibility, visibility and stability of handpiece while working

Air-rotor contra-angle handpiece