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.
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 property 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 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.
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 (ISO).
Dental burrs typically have shank diameters of either 1.6 mm (1/16 inches) or 2.35 mm (3/32 inches).
Read more, here.