View source for Engineering:Dental drill

{{short description|Dental instrument}}
[[File:Dentalhandpiece0111-26-05.jpg|right|thumb|300x300px|A high-speed dental handpiece.]]

[[File:Winkelstück 2009 46.JPG|thumb|Head of the dental drill]]

A '''dental drill''' or '''dental handpiece''' is a hand-held, mechanical instrument used to perform a variety of common [[Medicine:Dentistry|dental procedures]], including removing [[Medicine:Tooth decay|decay]], polishing fillings, performing cosmetic dentistry, and altering [[Medicine:Dental prosthesis|prostheses]].
The handpiece itself consists of internal mechanical components which initiate a rotational force 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 and [[Physics:Water cooling|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 [[Chemistry:Tungsten carbide|tungsten carbide]] or [[Chemistry:Diamond|diamond]].

== High-speed handpiece ==
High-speed handpieces may cut at speeds of up to 180,000 rpm. Depending on their mechanisms, they are classified as air turbine or speed-increasing. However, in a clinical context, air turbine handpieces are commonly referred to as "high-speeds." Handpieces have a [[Engineering:Chuck (engineering)|chuck]] or [[Engineering:Collet|collet]], for holding a cutter, called a burr or bur.

=== Mechanisms ===
==== Power ====

[[File:Turbineradjpeg.jpg|thumb|Air turbine used in a dental handpiece]]
[[File:SpeedToruqe.png|thumb|Correlation between rotational speed and torque]]
[[File:SpeedPower.png|thumb|Correlation between rotational speed and turbine output power]]
The turbine is powered by compressed air between 35 and 61 [[Pounds per square inch|pounds per square inch]] (~2,4 to 4,2 bar),<ref>{{cite web |url=https://www.kavo.com/download-center?product=2682&f[0]=field_resource_document_type%3A633&f[1]=field_resource_product%3A2682 |title=Instruction for Use MASTERtorque M9000L |website=kavo.com|date=2 March 2017 }}</ref><ref>{{cite web |title=Highspeed Handpiece Design |date=May 25, 2010 |publisher=American Dental Accessories |url=https://www.amerdental.com/blog/tech-tips-22/ |access-date=October 16, 2018}}</ref> which passes up the centre of the instrument and rotates a [[Engineering:Pelton wheel|Pelton wheel]] 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; 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 ====
High-speed friction generates tremendous heat within the burr. High-speed handpieces must consequently have an excellent water-cooling system. The standard is 50 ml/min of cooling water provided 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 utilized a system of halogen lamps and fiber-optic rods, but this method has several drawbacks: halogen bulbs decay over time and are costly to repair, and fiber-optic rods fracture readily if dropped and disintegrate through repeated autoclaving cycles.

LED technologies are now used in many sophisticated handpieces. LEDs have a longer operating life, produce more powerful light, and produce less heat.

== 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.<ref>{{cite journal |title=Electric Handpieces: An Overview of Current Technology |author=Gregori M. Kurtzman |publisher=AEGIS Communications |journal=Inside Dentistry |date=February 2007 |volume=3 |issue=2 |url=https://www.aegisdentalnetwork.com/id/2007/02/focus-on-electric-handpieces-an-overview-of-current-technology |access-date=October 15, 2018}}</ref>
For this reason, electric handpieces are also called speed-increasing handpieces, working at cutting speeds over 180,000 rpm.<ref>{{Cite book|title=A clinical guide to applied dental materials|last=Bonsor, Pearson|publisher=Churchill Livingstone Elsevier|year=2013|pages=329}}</ref>
* 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 ==
{| class="wikitable"
|+
!
!High speed
!Speed increasing 
|-
|'''Type of burr used'''
|Friction grip
|Friction grip
|-
|'''Power source'''
|Compressed air
|Electric  Micromotor
|-
| '''Torque'''
|Variable
|Constant
|-
|'''Motion of burr'''
|Rotation & Pecking
|Rotation only
|-
|'''Balance'''
|Usually neutral
|Motor end heavy
|}

== Slow speed handpiece ==
Slow speed handpieces work at a much slower rate that high speed and speed-increasing handpieces, and are usually driven by [[Physics:Pneumatic motor#Rotary vane motors|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 ==
[[File:Drill long.jpg|thumb|left|A collection of various burrs used in [[Medicine:Dentistry|dentistry]].]]
[[File:Dental rotary instruments - boreri.JPG|thumb|Dental rotary instruments - boreri]]
A dental burr or bur is a type of [[Engineering:Burr (cutter)|cutter]] used in a handpiece.  The burrs are usually made of [[Chemistry:Tungsten carbide|tungsten carbide]] or [[Chemistry:Diamond|diamond]].  The three parts of a burr are the head, the neck, and the shank.<ref name="summit">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. {{ISBN|0-86715-382-2}}.</ref>

The heads of some burrs (such as tungsten carbide burrs) contain the [[Engineering:Blade|blade]]s which remove material.  These blades may be positioned at different [[Angle|angle]]s in order to change the property of the burr. More obtuse angles will produce a negative [[Engineering:Rake angle|rake angle]], which increases the strength and [[Engineering:Tool wear|longevity]] of the burr.  More acute angles 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 seem to give better control and tactile feedback then carbide burrs, due to the fact that the diamonds are always in contact with the milled tooth in comparison to the single blades of the carbide burrs.<ref>{{cite web |url=https://www.researchgate.net/publication/266775908 |title=Comparison of Carbide and Diamond Burs for Class-II Preparations |date=2014 |last=Stevens |first=Lorin |last2=Malcolm |first2=Scott |last3=George |first3=Scott |last4=Palmer |first4=Timothy |last5=Martinez |first5=Alejandro |last6=Moeller |first6=Aaron |last7=Hein |first7=Cameron |last8=Christensen |first8=Gordon |via=[[Company:ResearchGate|ResearchGate]]}}</ref>

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.<ref name="summit" />  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 [[Organization:International Organization for Standardization|International Organization for Standardization]] (ISO).

Dental burrs typically have shank diameters of either 1.6&nbsp;mm (1/16 inches) or 2.35&nbsp;mm (3/32 inches).<ref>{{cite web |title=Guide to the Different Types of Dental Burs |publisher=Dentared Odontology Services |url=https://www.dentaltix.com/en/blog/guide-different-types-dental-burs |access-date=May 7, 2020}}</ref>

==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 [[Organization:Autoclave|autoclave]] after removing the drill, washing the instrument with water and lubricating it.<ref>"[http://www.praezimed.it/menutenzione-di-strumenti/manutenzione-contrangoli Maintenance Instruction for Dental Drills (Italian)]"</ref><ref>"[http://www.implantate.com/robert-koch-institut-hat-die-neuen-hygienerichtlinien-fuer-die-zahnarztpraxis-veroeffentlicht-bdiz-ma.html Hygiene Instructions for Dentists (German)]"</ref> The United States Food and Drug Administration classes burrs as "single-use devices",<ref>{{Cite web|url=http://www.dentaleconomics.com/articles/print/volume-104/issue-10/practice/infection-prevention/reusing-disposable-items-saving-money-or-risking-cross-contamination.html|title=Reusing disposable items: saving money or risking cross-contamination?|author=Mary Govoni|date=October 15, 2014|website=www.dentaleconomics.com|access-date=2017-03-02}}</ref> although they can be sterilised with proper procedures.

==History==
[[File:DentalDrillFootPowered.jpg|thumb|right|upright|Foot-powered dental drill]]
The Indus Valley civilization has yielded evidence of dentistry being practiced as far back as 7000 BC.<ref name=Coppa>Coppa, A. et al.  2006.  [http://www.nature.com/nature/journal/v440/n7085/pdf/440755a.pdf ''Early Neolithic tradition of dentistry'']. ''Nature''.  Volume 440.  6 April 2006. {{doi|10.1038/440755a}}</ref> This earliest form of dentistry involved curing tooth-related disorders with [[Engineering:Bow drill|bow drill]]s operated, perhaps, by skilled bead craftsmen.<ref>{{cite news |url=http://news.bbc.co.uk/1/hi/sci/tech/4882968.stm |title=Stone age man used dentist drill |work=BBC News |date=6 April 2006}}</ref> The reconstruction of this ancient form of dentistry showed that the methods used were reliable and effective.<ref>NBC News (2008). [http://www.nbcnews.com/id/12168308 ''Dig uncovers ancient roots of dentistry''].</ref> Cavities of 3.5&nbsp;mm depth with concentric grooves indicate use of a drill tool. The age of the teeth has been estimated at 9,000 years. In later times, mechanical hand drills were used. Like most [[Engineering:Drill#Hand tools|hand drills]], they were quite slow, with speeds of up to 15 [[Revolutions per minute|rpm]].  In 1864, {{wipe|United Kingdom}} dentist George Fellows Harrington invented a [[Engineering:Clockwork|clockwork]] dental drill named ''Erado''.<ref>{{cite web|url=https://www.bda.org/museum/collections/dental-equipment/clockwork-drill-and-dental-engine| title=BDA Museum: Collections: Dental equipment: Clockwork drill and dental engine |publisher=British Dental Association |date=7 June 2013 |access-date=9 September 2015}}</ref>  The device was much faster than earlier drills, but also very noisy.  In 1868, {{wipe|United States}} dentist George F. Green came up with a pneumatic dental drill powered by [[Engineering:Lever|pedal]]-operated [[Engineering:Bellows|bellows]].  James B. Morrison devised a pedal-powered burr drill in 1871. [[File:ChayesM33Handpiece.jpg|thumb|Chayes M33 with Buffalo drive belt.]]

The first electric dental drill was patented in 1875 by Green, a development that revolutionized dentistry. By 1914, electric dental drills could reach speeds of up to 3,000 [[Revolutions per minute|rpm]].  A second wave of rapid development occurred in the 1950s and 60s, including the development of the [[Physics:Pneumatic motor|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 knighted) 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 filed in October 1949.<ref>{{cite patent |country=NZ |number=104611 |status=patent |title=Pneumatic Dental Drilling Apparatus |pubdate=12-23-1952 |fdate=27-10-1949 |inventor=F.R. Callaghan |url=https://app.iponz.govt.nz/app/Extra/IP/Mutual/Browse.aspx?sid=638091611893919294}}</ref> This handpiece was driven by compressed air. 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.<ref>[http://www.kavo.com/functions/csdownload3.aspx?file=History_Banner_Turbinen_en.pdf&id=38225&org=003&key=f75a119947f217606e0dd24e773215d382de9e5eed84ca4365ec74cfa82a3a7b&key2=4b4e5113d2a3c22bb3d250563ff808758ae0e2ebc59d84036f2de57df20a5d3b History of Dental Turbines] {{webarchive|url=https://archive.today/20150428223209/http://www.kavo.com/functions/csdownload3.aspx?file=History_Banner_Turbinen_en.pdf&id=38225&org=003&key=f75a119947f217606e0dd24e773215d382de9e5eed84ca4365ec74cfa82a3a7b&key2=4b4e5113d2a3c22bb3d250563ff808758ae0e2ebc59d84036f2de57df20a5d3b |date=2015-04-28 }}</ref>

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.<ref>Handpiece, Use, Care and Maintenance", Franzel, Mattana. University Detroit Mercy School of Dentistry literature 2007</ref>

==Alternatives==

Starting in the 1990s, a number of alternatives to conventional rotary dental drills have been developed.  These include [[Engineering:Dental laser|dental laser]] systems,<ref>{{Cite news|url=https://www.wsj.com/articles/SB10001424127887323335404578447334250171190|title=To Cut Tooth Decay: A Laser vs. a Drill|last=Johannes|first=Laura|date=2013-04-29|newspaper=Wall Street Journal|issn=0099-9660|access-date=2016-09-20}}</ref> [[Medicine:Air abrasion|air abrasion]] devices (devices that combine small abrasive particles with pressurized air, essentially miniature [[Engineering:Sandblasting|sand blasters]]),<ref name="Huang Kim Arce Lawson 2019">{{cite journal | last1=Huang | first1=CT | last2=Kim | first2=J | last3=Arce | first3=C | last4=Lawson | first4=NC | title=Intraoral Air Abrasion: A Review of Devices, Materials, Evidence, and Clinical Applications in Restorative Dentistry. | journal=Compendium of Continuing Education in Dentistry | volume=40 | issue=8 | year=2019 | issn=1548-8578 | pmid=31478697 | pages=508–514}}</ref><ref name="Mandinic Vulicevic 2014 ">{{cite journal | last1=Mandinic | first1=Zoran | last2=Vulicevic | first2=Zoran | last3=Beloica | first3=Milos | last4=Radovic | first4=Ivana | last5=Mandic | first5=Jelena | last6=Carevic | first6=Momir | last7=Tekic | first7=Jasmina | title=The application of air abrasion in dentistry | journal=Srpski Arhiv Za Celokupno Lekarstvo | publisher=National Library of Serbia | volume=142 | issue=1–2 | year=2014 | issn=0370-8179 | doi=10.2298/sarh1402099m | pages=99–105| pmid=24684041 | doi-access=free }}</ref> and dental treatments with [[Chemistry:Ozone|ozone]] or silver diamine fluoride (SDF).<ref name="Tiwari 2017">{{cite journal | last1=Tiwari | first1=Sansriti | last2=Avinash | first2=Alok | last3=Katiyar | first3=Shashank | last4=Aarthi Iyer | first4=A. | last5=Jain | first5=Suyog | title=Dental applications of ozone therapy: A review of literature | journal=The Saudi Journal for Dental Research | publisher=Elsevier BV | volume=8 | issue=1–2 | year=2017 | issn=2352-0035 | doi=10.1016/j.sjdr.2016.06.005 | pages=105–111| s2cid=77862294 | doi-access=free }}</ref><ref name="Rosenblatt 2009">{{cite journal | last1=Rosenblatt | first1=A. | last2=Stamford | first2=T.C.M. | last3=Niederman | first3=R. | title=Silver Diamine Fluoride: A Caries "Silver-Fluoride Bullet" | journal=Journal of Dental Research | publisher=SAGE Publications | volume=88 | issue=2 | year=2009 | issn=0022-0345 | doi=10.1177/0022034508329406 | pages=116–125| pmid=19278981 | s2cid=30730306 }}</ref>

==References==

{{reflist|30em}}
* MedTerms definition for ''[http://www.medterms.com/script/main/art.asp?articlekey=16047 Drill, dental]''
* [https://web.archive.org/web/20060125085126/http://www.bda-dentistry.org.uk/museum/oral.cfm?ContentID=482 "Dental drills - enemy of the people?"] from the British Dental Association museum
* Australian Dental Journal:1 p59-62
* Dental History 




[[Category:Dental equipment]]

{{Sourceattribution|Dental drill}}