Dental burs, the tiny drill pieces for teeth! Dental burs are used in conjunction with the dentist's handpiece for cutting away hard tissue such as tooth and bone. There are a huge range of burs, with different materials, shapes and sizes to suit different situations and procedures. This bewildering range of options can leave you confused and unsure of what bur you require.
Bur Shanks
Shanks make up the long part of the bur piece. Shanks have different ends to attach to different types of handpieces and are available in different lengths to enable attachment to specific handpieces.
Long Straight Shank Burs (HP)
Long straight shanks are used on slow speed handpieces, most commonly used for diamond cutting discs. Long straight shanks are also used in surgery procedures.
Latch-type Shank Burs (RA)
This type of shank is generally 20mm in length with a 2.35mm diameter and fits in low speed handpieces and contra angles. Latch-type shanks often available with the same shapes as Friction grip shanks.
Friction Grip Shank Burs (FG)
Friction grips are used in conjunction with carbide and diamond head burs. Friction grips are used with high speed handpieces and like latch-type shanks they are generally around 20mm in length with a 1.6mm diameter.
Bur Materials
Burs are available in a range of materials. Each material has its pros an cons, making them suitable for different tasks.
Diamond Burs
Diamond burs are most commonly used with high speed handpieces, meaning they are most commonly available as a friction grip shank. Diamond is the hardest material available and is used to grind away tooth tissue, usually enamel. The grinding motion of a diamond bur leaves a rough finish.
Diamond burs have a short lifespan due to a pronounced decrease is cutting effectiveness. Diamond burs often get clogged with debris, the grinding motion also quickly wears down the instrument. Diamond burs come in an array of shapes and are available in a range of grits; from ultra fine to super coarse. When cutting away porcelain restorative material diamond burs are very effective.
Tungsten Carbide Burs
Carbide burs are made of tungsten carbide, a material that is 3 times stiffer than steel. Because of it is such a hard material it is able to maintain sharpness, making it an effective cutting tool. Much like diamond burs, carbide burs are available in a variance of shapes. The cuts made in the head of the bur make them effective cutting instruments as there is very little build up in debris.
Carbide burs cut and chip away the tooth structure rather than grinding as diamond burs do, this leaves a much smoother finish than diamond burs. Carbide burs are better handling for removing metal based restorations, they are also effective for trimming and finishing macro-filled and hybrid composites. Carbide burs are most commonly available as a friction grip shank but RA latch type shanks are also widely available.
Steel Burs
Steel burs provide an economical solution used for cavity preparation and dentine removal. Steel burs are softer, more flexible and also more resistant to chipping and breaking than carbide burs, although they're more flexible this does make them blunt quicker than a carbide bur. Steel burs are most commonly available with a latch type RA shank.
Bur Shapes
There is daunting range of shapes available which can make it extremely hard to decide which suits your situation best. Different flute angles create different cutting characteristics, making each bur appropriate for a particular task. Operative (cavity preparation) burs have deep and wide flutes to allow for more aggressive enamel cutting. These burs will usually be straight bladed or crosscut. Trimming and finishing burs will have more blades that are closer together and much shallower making them perfect for fine finishing and polishing. The most used bur head shapes include round, pear, cross-cut tapered fissure, cylinder and inverted cone.
Round Burs
Round burs are used for:
- cavity preparation
- creating access points
- creating undercuts
- creating channels for luxator blades in extraction
Round burs come in a size range from 1/4 to 10.
Pear Burs
Pear burs are used for:
- Cavity preparation
- Creating access points
- Splitting roots of small teeth
Cross-cut Tapered Fissure Burs
Cross-cut burs have more cuts in the blade to create a more efficient cutting process, cutting much quicker due to less debris build up. Crosscut tapered fissure burs are used for:
- Sectioning multi-rooted teeth
- reducing crown height
Finishing Burs
Finishing burs are used for finishing restorations, soft tissue re-contouring, enameloplasty & odontoplasty. Finishing burs can be obtained as 12 or 30 bladed burs in carbide or diamond head in a variety of shapes. Finishing burs are also available in white stone for composite and green stone for amalgam.
Dental Bur Numbering Systems
Due to the huge array of shapes and sizes of burs standard numbering systems were put in place to easily identify burs. There are two main systems that are used; the U.S. and ISO (International Standards Organisation) numbering systems. The U.S numbering system is most commonly used for carbide burs and is generally a 1 to 4 digit number dependant on the bur.
The ISO numbering system was introduced in 1979, labelling dental burs with a 15 digit code that are broken down into 6 sections:
A. Type of bur e.g. diamond/carbide
B. Type of shank e.g. straight (HP)
C. Total bur length
D. Head shape e.g. ball head
E. Indication of grit e.g. coarse/fine
F. Size of maximum head diameter
