A dental drill or dental handpiece is a hand-held, mechanical instrument used to perform a variety of common dental procedures, including removing decay, polishing fillings, performing cosmetic dentistry, and altering prostheses. The handpiece itself consists of internal mechanical components that 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 cooling water-spray system to also be incorporated into certain handpieces; this improves visibility, accuracy, and the overall success of the procedure. The burrs are usually made of tungsten carbide or diamond.
Depending on their mechanisms, handpieces are classified as air turbine or electric (including speed-increasing). However, in a clinical context, air turbine handpieces are commonly referred to as "high-speeds". Handpieces have a chuck or collet, for holding a cutter, called a burr or bur.
The turbine is powered by compressed air between 35 and 61 pounds per square inch (~2,4 to 4,2 bar), [1] [2] which passes up the centre of the instrument and rotates a 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:
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.
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.
While air turbine-powered handpieces can reach extremely high speeds (between 250,000 and 420,000 rpm) with low torque, electric handpieces typically operate at lower speeds (20 to 200,000 rpm) with higher torque. Some electric handpieces, called speed-increasing handpieces, utilize gear ratios to boost their rotational speed. [3]
Air driven | Electric | |
---|---|---|
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 |
Noise | Louder | Quieter |
Slow-speed handpieces work at a much slower rate than high-speed electric or air turbine handpieces. Slow-speed handpieces are usually driven by rotary vane motors, instead of air turbines. They work at a speed between 600 and 25,000 rpm. The internal gearing is 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.
Generally used for operative procedures such as the removal of dental caries or for polishing enamel or restorative materials. A straight, slow-speed handpiece is generally indicated for the extra oral adjustment and polishing of acrylic and metal.
Designed to work at slower speeds.
The main indications for use include endodontic canal preparation, implant placement, and prophylaxis.
Endodontic canals are prepared using a slow-rotating file. It is imperative that torque be controlled in order to prevent endodontic file separation during use.
A dental burr, or bur, is a type of cutter used in a handpiece. The burrs are usually made of tungsten carbide or diamond. The three parts of a burr are the head, the neck, and the shank. [4]
The heads of some burrs (such as tungsten carbide burrs) contain the blades which remove material. These blades may be positioned at different angles in order to change the properties of the burr. More obtuse angles will produce a negative rake angle, which increases the strength and longevity of the burr. More acute angles will produce a positive rake angle, which has a sharper blade but dulls more quickly. The heads of other commonly used burrs are covered in a fine grit that has a similar cutting function to blades (e.g., high-speed diamond burrs). Diamond burrs seem to give better control and tactile feedback than 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. [5]
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. [4] 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 (ISO).
Dental burrs typically have shank diameters of either 1.6 mm (1/16 inches) or 2.35 mm (3/32 inches). [6]
The instrument needs to be disinfected or sterilized after every use to prevent infection during subsequent 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 after removing the drill, washing the instrument with water, and lubricating it. [7] [8] The United States Food and Drug Administration classes burrs as "single-use devices", [9] although they can be sterilised with proper procedures.
The Indus Valley civilization has yielded evidence of dentistry being practiced as far back as 7000 BC. [10] This earliest form of dentistry involved curing tooth-related disorders with bow drills operated, perhaps, by skilled bead craftsmen. [11] The reconstruction of this ancient form of dentistry showed that the methods used were reliable and effective. [12] Cavities of 3.5 mm depth with concentric grooves indicate the 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 hand drills, they were quite slow, with speeds of up to 15 rpm. In 1864, British dentist George Fellows Harrington invented a clockwork dental drill named Erado. [13] The device was much faster than earlier drills, but also very noisy. In 1868, American dentist George F. Green came up with a pneumatic dental drill powered by pedal-operated bellows. James B. Morrison devised a pedal-powered burr drill in 1871.
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 rpm. A second wave of rapid development occurred in the 1950s and 1960s, including the development of the air turbine drill.
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. [14] 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. [15]
Current iterations can operate at up to 800,000 rpm; however, the most common is a 400,000 rpm "high speed" handpiece for precision work, complemented by a "low speed" handpiece operating at a speed that is dictated by a micromotor, which creates the momentum (maximum up to 40,000 rpm) for applications requiring higher torque than a high-speed handpiece can deliver. [16]
Starting in the 1990s, a number of alternatives to conventional rotary dental drills have been developed. These include dental laser systems, [17] air abrasion devices (devices that combine small abrasive particles with pressurized air, essentially miniature sand blasters), [18] [19] and dental treatments with ozone or silver diamine fluoride (SDF). [20] [21]
The Tesla turbine is a bladeless centripetal flow turbine invented by Nikola Tesla in 1913. It functions as nozzles apply a moving fluid to the edges of a set of discs. The engine uses smooth discs rotating in a chamber to generate rotational movement due to the momentum exchange between the fluid and the discs. The discs are arranged in an orientation similar to a stack of CDs on an axle.
A drill is a tool used for making round holes or driving fasteners. It is fitted with a bit, either a drill or driver chuck. Hand-operated types are dramatically decreasing in popularity and cordless battery-powered ones proliferating due to increased efficiency and ease of use.
Aircraft engine controls provide a means for the pilot to control and monitor the operation of the aircraft's powerplant. This article describes controls used with a basic internal-combustion engine driving a propeller. Some optional or more advanced configurations are described at the end of the article. Jet turbine engines use different operating principles and have their own sets of controls and sensors.
A drill bit is a cutting tool used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation. The drill will grasp the upper end of a bit called the shank in the chuck.
A torque converter is a device, usually implemented as a type of fluid coupling, that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the prime mover to the automatic gear train, which then drives the load. It is thus usually located between the engine's flexplate and the transmission. The equivalent device in a manual transmission is the mechanical clutch.
A continuously variable transmission (CVT) is an automated transmission that can change through a continuous range of gear ratios. This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant angular velocity while the vehicle moves at varying speeds.
A pneumatic motor, or compressed-air engine, is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed-air energy to mechanical work through either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor, piston air motor, air turbine or gear type motor.
Milling cutters are cutting tools typically used in milling machines or machining centres to perform milling operations. They remove material by their movement within the machine or directly from the cutter's shape.
Burrs or burs are small cutting tools; not to be confused with small pieces of metal formed from cutting metal, used in die grinders, rotary tools, or dental drills. The name may be considered appropriate when their small-sized head is compared to a bur or their teeth are compared to a metal burr.
The power band of an internal combustion engine or electric motor is the range of operating speeds under which the engine or motor is able to output the most power, that is, the maximum energy per unit of time. This usually means that maximum acceleration can be achieved inside this band. While engines and motors have a large range of operating speeds, the power band is usually a much smaller range of engine speed, only half or less of the total engine speed range.
Dental instruments are tools that dental professionals use to provide dental treatment. They include tools to examine, manipulate, treat, restore, and remove teeth and surrounding oral structures.
A diamond tool is a cutting tool with diamond grains fixed on the functional parts of the tool via a bonding material or another method. As diamond is a superhard material, diamond tools have many advantages as compared with tools made with common abrasives such as corundum and silicon carbide.
Wind turbine design is the process of defining the form and configuration of a wind turbine to extract energy from the wind. An installation consists of the systems needed to capture the wind's energy, point the turbine into the wind, convert mechanical rotation into electrical power, and other systems to start, stop, and control the turbine.
The Turboglide is a Chevrolet constant torque, continuously variable automatic transmission first offered as an option on Chevrolet V8 passenger cars for 1957. It consisted of a turbine-driven planetary gearbox with a 'switch pitch' dual-pitch torque converter stator. It had a die-cast aluminum transmission case, like Packard's Ultramatic of 1956. Turboglide cost about $50 more than the Powerglide 2-speed automatic. It was available in all V8-powered 1957-1961 Chevrolet models except the Corvette. General Motors produced 646,000 of these transmissions during its production.
A cold saw is a circular saw designed to cut metal which uses a toothed blade to transfer the heat generated by cutting to the chips created by the saw blade, allowing both the blade and material being cut to remain cool. This is in contrast to an abrasive saw, which abrades the metal and generates a great deal of heat absorbed by the material being cut and saw blade.
Tooth polishing procedures are done to smooth the surfaces of teeth and restorations. The purpose of polishing is to remove extrinsic stains, remove dental plaque accumulation, increase aesthetics and to reduce corrosion of metallic restorations. Tooth polishing has little therapeutic value and is usually done as a cosmetic procedure after debridement and before fluoride application. Common practice is to use a prophy cup—a small motorized rubber cup—along with an abrasive polishing compound.
University of Otago Faculty of Dentistry is one of the faculties of the University of Otago.
Endodontic files and reamers are surgical instruments used by dentists when performing root canal treatment. These tools are used to clean and shape the root canal, with the concept being to perform complete chemomechanical debridement of the root canal to the length of the apical foramen. Preparing the canal in this way facilitates the chemical disinfection to a satisfactory length but also provides a shape conducive to obturation.
W&H Dentalwerk is a manufacturer of dental handpieces and turbines based in Austria.
A dental aerosol is an aerosol that is produced from dental instrument, dental handpieces, three-way syringes, and other high-speed instruments. These aerosols may remain suspended in the clinical environment. Dental aerosols can pose risks to the clinician, staff, and other patients. The heavier particles contained within the aerosols are likely to remain suspended in the air for relatively short period and settle quickly onto surfaces, however, the lighter particles may remain suspended for longer periods and may travel some distance from the source. These smaller particles are capable of becoming deposited in the lungs when inhaled and provide a route of diseases transmission. Different dental instruments produce varying quantities of aerosol, and therefore are likely to pose differing risks of dispersing microbes from the mouth. Air turbine dental handpieces generally produce more aerosol, with electric micromotor handpieces producing less, although this depends on the configuration of water coolant used by the handpiece.