A dental bur is a small, rotating instrument that serves as the “drill bit” in the dentist’s handpiece, designed to cut or grind hard tissues and materials with precision. These tools are fundamental for a wide array of procedures, ranging from preparing a tooth for a filling to shaping a crown. The bur’s function is to enable the precise removal of tissue, such as decayed material, old restorations, or tooth structure, allowing for the accurate shaping required for successful restorative dentistry. Selecting the correct bur, based on its material, shape, size, and grit, is integral to achieving the desired clinical outcome while preserving healthy tooth structure.
Composition and Manufacturing Materials
The performance of a dental bur is largely determined by the material used to construct its working head, with three main types dominating clinical practice: Tungsten Carbide, Diamond, and Stainless Steel.
Tungsten Carbide burs are formed from a compound that is approximately three times harder than conventional steel, giving them exceptional cutting efficiency and durability. These burs feature sharp, multi-bladed heads that “cut” or “chip” away tooth structure, making them preferred for rapid excavation of decay, preparing cavities, and cleanly removing old metal fillings or restorations.
Diamond burs, in contrast, operate by grinding rather than cutting, using tiny particles of industrial-grade diamond bonded onto a stainless steel substrate. Since diamond is the hardest known natural material, these burs are highly effective for abrading the hardest tissues like enamel, porcelain, and zirconia. They are particularly useful for bulk reduction of tooth structure and shaping teeth for crowns and veneers, where the grinding action leaves a strong, consistent surface.
Stainless Steel burs are softer and more flexible than their carbide or diamond counterparts, which makes them less prone to breakage but also causes them to dull more quickly. These burs are frequently used in slower-speed handpieces for more delicate tasks, such as removing soft, decayed dentin without risking damage to the underlying pulp. Their gentler cutting action and cost-effectiveness make them a reliable choice for initial cavity preparation and in pediatric dentistry procedures.
Understanding Bur Shapes and Sizes
The geometric design of the bur head dictates its specific role in a dental procedure, with numerous shapes available to address different clinical needs. The Round bur, which features a spherical head, is commonly used for initial access into a tooth, precise removal of carious (decayed) tissue, and creating channels for specialized instruments.
The Inverted Cone bur has a shape resembling a cone with its base pointing toward the shank, and it is frequently employed for creating undercuts within a cavity preparation. These undercuts are small internal retention features that help mechanically lock a filling material into place, and the bur’s form is also effective for flattening the floors of a prepared cavity. A Fissure bur, which can be cylindrical or tapered, is designed with straight sides to create parallel walls and sharp internal line angles within the tooth preparation. The Tapered Fissure bur is particularly useful for shaping teeth for crowns and inlays, providing the necessary convergence for the final restoration to fit accurately.
The Pear bur combines features of the round and fissure shapes, presenting as a slightly tapered cylinder with a rounded tip, making it a versatile tool for general-purpose decay removal and shaping. Its geometry allows for both initial entry and subsequent contouring of the cavity walls. Each shape is also available in a wide range of head diameters, meaning a dentist can select a small Round bur for pinpoint decay removal or a large Tapered bur for rapid reduction of a whole tooth surface.
The Role of Grit and Shank Types
Beyond composition and shape, two other factors determine a bur’s function: its grit and its shank type. Grit relates to the abrasive quality of the bur’s surface, particularly for diamond burs, and is standardized using a color-coding system to indicate the size of the abrasive particles.
Coarser grits, such as those color-coded Black or Green, utilize larger diamond particles (up to 255 microns) and are used for rapid, bulk material reduction, like removing large amounts of enamel. Finer grits, typically indicated by Red or Yellow bands, have much smaller particles (as low as 25 microns) and are reserved for the final stages of a procedure. The progression from a coarse to a fine grit bur is a standard technique to achieve the smoothest possible finish on the tooth.
The shank is the smooth, cylindrical end that connects the bur to the dental handpiece, and its design dictates the speed and torque at which the bur operates. There are three primary shank types used in dentistry.
Friction Grip (FG) Shank
The Friction Grip (FG) shank is smooth and small in diameter (1.6 mm). It is designed to lock into high-speed handpieces that can rotate at speeds exceeding 300,000 revolutions per minute.
Latch Type (RA) and Straight (HP) Shanks
The Latch Type (RA) shank features a small notch at its base. This type is used with slower-speed, contra-angle handpieces, operating at a maximum of around 40,000 RPM for controlled procedures like polishing and dentin removal. The Straight (HP) shank is the largest and is primarily used in laboratory handpieces or specialized surgical procedures outside the mouth.