Dental drill

A dental drill or 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 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 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 or diamond. 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 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: 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.