Dental drill

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), 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.