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A dental drill or handpiece is a hand-held, mechanical instrument used to perform a variety of common dental procedures, including removing
decay Decay may refer to: Science and technology * Bit decay, in computing * Software decay, in computing * Distance decay, in geography * Decay time (fall time), in electronics Biology * Decomposition of organic matter * Tooth decay (dental caries ...
, polishing fillings, performing
cosmetic dentistry Cosmetic dentistry is generally used to refer to any dental work that improves the appearance (though not necessarily the functionality) of teeth, gums and/or bite. It primarily focuses on improvement in dental aesthetics in color, position, shape, ...
, and altering
prostheses In medicine, a prosthesis (plural: prostheses; from grc, πρόσθεσις, prósthesis, addition, application, attachment), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trau ...
. The handpiece itself consists of internal mechanical components which initiate a
rotational force In physics and mechanics, torque is the rotational equivalent of linear force. It is also referred to as the moment of force (also abbreviated to moment). It represents the capability of a force to produce change in the rotational motion of the ...
and provide power to the cutting instrument, usually a dental burr. The type of apparatus used clinically will vary depending on the required function dictated by the dental procedure. It is common for a
light source Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terah ...
and cooling water-spray system to also be incorporated into certain handpieces; this improves visibility, accuracy and overall success of the procedure. The burrs are usually made of
tungsten carbide Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
or
diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, ...
.


High-speed handpiece

High-speed handpieces work at cutting speeds over 180,000 rpm. They are technically categorised into ''air turbine'' and ''speed-increasing'' depending on their mechanisms. In a clinical setting, however, air turbine handpieces are most often referred to as "high-speeds". Handpieces have a
chuck Chuck is a masculine given name or a nickname for Charles or Charlie. It may refer to: People Arts and entertainment * Chuck Alaimo, American saxophonist, leader of the Chuck Alaimo Quartet * Chuck Barris (1929–2017), American TV producer * C ...
or collet, for holding a cutter, called a burr or bur.


Mechanisms


Power

The turbine is powered by compressed air between 35 and 61 pounds per square inch (~2,4 to 4,2 bar), which passes up the centre of the instrument and rotates a
Pelton wheel The Pelton wheel or Pelton Turbine is an impulse-type water turbine invented by American inventor Lester Allan Pelton in the 1870s. The Pelton wheel extracts energy from the impulse of moving water, as opposed to water's dead weight like the trad ...
in the head of the handpiece. The centre of the windmill (chuck) is surrounded by ''bearing housing'', which holds a ''friction-grip burr'' firmly & centrally within the instrument. Inside the bearing housing are small, lubricated ball-bearings (stainless steel or ceramic) which allow the shank of the burr to rotate smoothly along a central axis with minimal friction. The complete rotor is fixed with O-Rings in the head of the high speed. The O-Rings allow the system to become perfect centric during the idle speed but allow a small movement of the rotor within the head. Failure of the burr to run centrally causes a number of clinical defects: * The burr will
judder Telecine ( or ) is the process of transferring film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process. Telecine enables a motion picture, captured originally on ...
; this will cause excessive, damaging vibrations leading to cracking and ''crazing'' in the material being cut. It is also an unpleasant experience for the patient. * Eccentric cutting - this will result in irregular removal of the surface, meaning more tissue than necessary is removed. * Decreased control - due to irregular cutting, it is more difficult for the dentist to control movements


Cooling

The friction produced by high-speeds creates significant heat within the burr. It is therefore critical for high-speed handpieces to have an effective water-cooling system. The standard is a cooling water of minimum 50 ml/min that is delivered through 3 to 5 spray hole jets.


Illumination

Many modern handpieces now have a light in close proximity to the burr. The light is directed at the cutting surface as to assist with intra-operative vision. Older handpieces used a system of ''halogen bulbs'' and ''fibre-optic rods'', however, there are a number of disadvantages to this system: halogen bulbs deteriorate with time and are expensive to replace, and fibre-optic rods fracture easily if dropped and deteriorate during repeated
autoclaving An autoclave is a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform steriliza ...
cycles. More modern handpieces now use LED systems. Advantages of LEDs include a longer working life, more intense light and minimal heat production.


Speed-increasing handpiece

Electric motors cannot turn as fast as air turbines. To power a high-speed handpiece, gears are needed to increase the speed of an electric motor, often by a ratio of 1:5. For this reason, electric handpieces are also called speed-increasing handpieces, working at cutting speeds over 180,000 rpm. * Speed-increasing handpiece is driven by electrical motor, also known as micromotor. * The power to the handpiece is provided by the micromotor. * Within the handpiece is internal gearings which allow the friction grip burr to rotate at a constant speed independent of torque. * Therefore, the power is provided by micromotor and internal gearings.


Torque

* Torque is the ability of burr to continually rotate with the same speed and cut even when pressure is applied * As the speed of a handpiece increases its torque subsequently decreases (slow-speed handpieces have high torque, whereas high-speed handpieces, like the air turbine system, have a low torque) * The free running speed of 1:5 speed-increasing handpiece is the same as its cutting speed, thus 40,000 motor speed x5= 200,000 rpm burr speed. * Electrical motor maintains the 200,000 rpm speed and provides consistent power so torque will be maintained, depending on the electronic control parameters.


Comparison of high speed and speed increasing handpieces


Slow speed handpiece

Slow speed handpieces work at a much slower rate that high speed and speed-increasing handpieces, and are usually driven by rotary vane motors, instead of air turbines. They work at a speed between 600 and 25,000 rpm. The internal gearings are very similar to that of a speed-increasing handpiece. The main difference between the two is that slow speed has internal gearing and they can use both a latch grip burr and a friction grip burr.


Indications for use

Generally used for operative procedures such as the removal of dental caries or for polishing enamel or restorative materials. Straight slow speed handpiece is generally indicated for the extra oral adjustment and polishing of acrylic and metals.


Speed decreasing handpiece

Designed to work at slower speeds.


Indications for use

The main indications for use include endodontic canal preparation, implant placement and prophylaxis.


Endodontic canal preparation

Endodontic canals are prepared using a slow rotating file. It is imperative that torque is controlled in order to prevent endodontic file separation during use. * Implant placement - In order to prevent heat damage to bone during implant placement speed decreasing handpiece is used. * Prophylaxis - Prophylaxis with the use of speed decreasing handpiece ensures that less heat is produced and thus less risk of pulpal damage by heat transmission.


Dental burr

A dental burr or bur is a type of cutter used in a handpiece. The burrs are usually made of
tungsten carbide Tungsten carbide (chemical formula: WC) is a chemical compound (specifically, a carbide) containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into ...
or
diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, ...
. The three parts to a burr are the head, the neck, and the shank.Summit, James B., J. William Robbins, and Richard S. Schwartz. "Fundamentals of Operative Dentistry: A Contemporary Approach." 2nd edition. Carol Stream, Illinois, Quintessence Publishing Co, Inc, 2001. Pages 139 - 143. . The heads of some burrs (such as tungsten carbide burrs) contain the
blade A blade is the portion of a tool, weapon, or machine with an edge that is designed to puncture, chop, slice or scrape surfaces or materials. Blades are typically made from materials that are harder than those they are to be used on. Historic ...
s which remove material. These blades may be positioned at different
angle In Euclidean geometry, an angle is the figure formed by two Ray (geometry), rays, called the ''Side (plane geometry), sides'' of the angle, sharing a common endpoint, called the ''vertex (geometry), vertex'' of the angle. Angles formed by two ...
s in order to change the property of the burr. More obtuse angles will produce a negative
rake angle Rake angle is a parameter used in various cutting and machining processes, describing the angle of the cutting face relative to the work. There are three types of rake angles: ''positive'', ''zero'' or ''neutral'', and ''negative''. * Positive ...
which increases the
strength Strength may refer to: Physical strength *Physical strength, as in people or animals * Hysterical strength, extreme strength occurring when people are in life-and-death situations *Superhuman strength, great physical strength far above human c ...
and
longevity The word " longevity" is sometimes used as a synonym for "life expectancy" in demography. However, the term ''longevity'' is sometimes meant to refer only to especially long-lived members of a population, whereas ''life expectancy'' is always d ...
of the burr. More
acute angle In Euclidean geometry, an angle is the figure formed by two rays, called the '' sides'' of the angle, sharing a common endpoint, called the ''vertex'' of the angle. Angles formed by two rays lie in the plane that contains the rays. Angles ar ...
s will produce a positive rake angle which has a sharper blade, but which dulls more quickly. The heads of other commonly used burrs are covered in a fine grit which has a similar cutting function to blades (e.g. high speed diamond burrs). Diamond burrs seems to give better control and tactile feedback then carbide burs, due to the fact that the diamonds are always in contact with the milled tooth in comparison to the single blades at the carbide burrs. There are various shapes of burrs that include round, inverted cone, straight fissure, tapered fissure, and pear-shaped burrs. Additional cuts across the blades of burrs were added to increase cutting efficiency, but their benefit has been minimized with the advent of high-speed handpieces. These extra cuts are called crosscuts. Due to the wide array of different burrs, numbering systems to categorise burrs are used and include a US numbering system and a numbering system used by the
International Organization for Standardization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Ar ...
(ISO). Dental burrs typically have shank diameters of either 1.6 mm (1/16 inches) or 2.35 mm (3/32 inches).


Maintenance

The instrument needs to be disinfected or sterilized after every usage to prevent infection during succeeding incisions. Due to the mechanical structure of the device, this must not be done with alcoholic disinfectant, as that would destroy the lubricants. Instead it has to be done in an
autoclave An autoclave is a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform sterilizati ...
after removing the drill, washing the instrument with water and lubricating it. The
United States Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food s ...
classes burrs as "single-use devices", although they can be sterilised with proper procedures.


History

The
Indus Valley civilization The Indus Valley Civilisation (IVC), also known as the Indus Civilisation was a Bronze Age civilisation in the northwestern regions of South Asia, lasting from 3300 BCE to 1300 BCE, and in its mature form 2600 BCE to 1900&n ...
has yielded evidence of dentistry being practiced as far back as 7000 BC.Coppa, A. et al. 2006.
''Early Neolithic tradition of dentistry''
''Nature''. Volume 440. 6 April 2006.
This earliest form of dentistry involved curing tooth related disorders with
bow drill A bow drill is a simple hand-operated type of tool, consisting of a rod (the ''spindle'' or ''drill shaft'') that is set in rapid rotary motion by means of a cord wrapped around it, kept taut by a bow which is pushed back and forth with one han ...
s operated, perhaps, by skilled bead craftsmen. The reconstruction of this ancient form of dentistry showed that the methods used were reliable and effective. Cavities of 3.5 mm depth with concentric grooves indicate use of a drill tool. The age of the teeth has been estimated at 9000 years. In later times, mechanical hand drills were used. Like most hand drills, they were quite slow, with speeds of up to 15
rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
. In 1864,
British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories, and Crown Dependencies. ** Britishness, the British identity and common culture * British English, ...
dentist
George Fellows Harrington George may refer to: People * George (given name) * George (surname) * George (singer), American-Canadian singer George Nozuka, known by the mononym George * George Washington, First President of the United States * George W. Bush, 43rd President ...
invented a
clockwork Clockwork refers to the inner workings of either mechanical devices called clocks and watches (where it is also called the movement) or other mechanisms that work similarly, using a series of gears driven by a spring or weight. A clockwork mec ...
dental drill named ''Erado''. The device was much faster than earlier drills, but also very noisy. In 1868,
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
dentist George F. Green came up with a pneumatic dental drill powered with
pedal A pedal (from the Latin '' pes'' ''pedis'', "foot") is a lever designed to be operated by foot and may refer to: Computers and other equipment * Footmouse, a foot-operated computer mouse * In medical transcription, a pedal is used to control p ...
-operated
bellows A bellows or pair of bellows is a device constructed to furnish a strong blast of air. The simplest type consists of a flexible bag comprising a pair of rigid boards with handles joined by flexible leather sides enclosing an approximately airtigh ...
.
James B. Morrison James is a common English language surname and given name: *James (name), the typically masculine first name James * James (surname), various people with the last name James James or James City may also refer to: People * King James (disambiguat ...
devised a pedal-powered burr drill in 1871. The first
electric Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...
dental drill was patented in 1875 by Green, a development that revolutionized dentistry. By 1914, electric dental drills could reach speeds of up to 3000
rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
. A second wave of rapid development occurred in the 1950s and 60s, including the development of the air turbine drill.


Contra angle

The modern incarnation of the dental drill is the air turbine (or air rotor) ''contra angle'' handpiece, where the shaft of the rotary instrument is at an angle allowing it to reach less accessible areas of the mouth for dental work. The contra angle was invented by John Patrick Walsh (later
knight A knight is a person granted an honorary title of knighthood by a head of state (including the Pope) or representative for service to the monarch, the church or the country, especially in a military capacity. Knighthood finds origins in the Gr ...
ed) and members of the staff of the Dominion Physical Laboratory (DPL) Wellington, New Zealand. The first official application for a provisional patent for the handpiece was granted in October 1949. This handpiece was driven by compressed air. The final model is held by the Commonwealth Inventions development Board in Canada. The New Zealand patent number is No/104611. The patent was granted in November to John Patrick Walsh who conceived the idea of the contra angle air-turbine handpiece after he had used a small commercial-type air grinder as a straight handpiece. Dr. John Borden developed it in America and it was first commercially manufactured and distributed by the DENTSPLY Company as the Borden Airotor in 1957. Borden Airotors soon were also manufactured by different other companies like KaVo Dental, which built their first one in 1959. Current iterations can operate at up to 800,000 rpm, however, most common is a 400,000 rpm "high speed" handpiece for precision work complemented with a "low speed" handpiece operating at a speed that is dictated by a micromotor which creates the momentum (max up to 40,000 rpm) for applications requiring higher torque than a high-speed handpiece can deliver.


Alternatives

Starting in the 1990s, a number of alternatives to conventional rotary dental drills have been developed. These include
dental laser A dental laser is a type of laser designed specifically for use in oral surgery or dentistry. In the United States, the use of lasers on the gums was first approved by the Food and Drug Administration in the early 1990s, and use on hard tissue lik ...
systems,
air abrasion Air abrasion is a dental technique that uses compressed air to propel a thin stream of abrasive particles—often aluminum oxide or silica—through a specialized hand-piece to remove tooth tissue and decay before being suctioned away, similar to s ...
devices (devices that combine small abrasive particles with pressurized air, essentially miniature sand blasters), and dental treatments with
ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...
or
silver diamine fluoride Silver diammine fluoride (SDF), also known as silver diamine fluoride in most of the dental literature, (although this is a chemical misnomer) is a topical medication used to treat and prevent dental caries (tooth decay) and relieve dentinal hype ...
(SDF).


References

* MedTerms definition for
Drill, dental
'
"Dental drills - enemy of the people?"
from the
British Dental Association The British Dental Association (BDA) is a registered trade union for dentists in the United Kingdom. Its stated mission is to "promote the interests of members, advance the science, arts and ethics of dentistry and improve the nation's oral he ...
museum * Australian Dental Journal:1 p59-62 * Dental History definition for
Rotors, dental
' {{Dentistry Dental equipment