US No. 558 Bur – Busch Straight Fissure Carbide & Steel, Made in Germany

The US No. 558 is the American number for a straight fissure bur with a 1.2 mm head (ISO size 012): a parallel-sided cylinder with a flat end, so it cuts straight walls and a flat floor in one motion. Busch & Co. manufactures it in Germany as Busch No. 31 012 and Busch No. 36 012 (plus 2 further variants below). Every US No. 558 on this page is a genuine Busch instrument and ships from our US warehouse.

Which US No. 558 Do You Need?

FG (friction grip, 1.6 mm shank, high-speed handpiece). HP (2.35 mm shank, straight handpiece). FG-XL (friction grip, 25 mm surgical length). See the Busch Bur Size Chart for head and shank dimensions.

Clinical Uses of the US No. 558

• Cavity preparation: opening through enamel and establishing the straight walls and flat floor of Class I and Class II preparations, including proximal boxes.
• Restoration removal: cutting out old amalgam and composite; crosscut versions clear the debris instead of packing with it.
• Sectioning: dividing crowns and multi-rooted teeth, where the surgical-length versions add reach and visibility.
• Laboratory and denture work: the HP carbide and steel versions trim acrylic, adjust denture bases and reduce plaster models in the straight handpiece.

At 1.2 mm the No. 558 is the standard operative size.

The 558L (Busch 31L 012) carries a longer cutting head for deeper boxes and taller walls. The 558X is the surgical version: the same cutting head on a 25 mm FG-XL shank for reach when sectioning teeth and roots, with a rounded end.

The No. 558 is crosscut; its plain-cut twin in the same shape and size is the US No. 58 (Busch 21 012). Crosscut blades cut faster and clear debris; when you need a smooth wall or a finish line, follow with the plain-cut twin or a finishing bur.

Speed and Technique

Run the FG versions in the high-speed handpiece with continuous water spray and light, intermittent pressure; let the blades do the work. HP versions run at laboratory speed in the straight handpiece. Maximum recommended speeds for every Busch shape are in our Dental Bur Speed Chart, and reprocessing steps in the Bur Sterilization Guide.

Made in Germany by Busch & Co.

Busch & Co. has manufactured rotary instruments in Engelskirchen, Germany since 1905. Every instrument on this page is a genuine Busch product, precision-ground on a concentric shank under ISO-certified quality management and guaranteed to arrive free of manufacturing defects under our Busch arrival guarantee.

FAQ

What is the Busch number for a US 558 bur? Busch No. 31 012 in carbide (FG/HP); Busch No. 36 012 in steel (HP). The 558L is Busch 31L 012; the 558X is Busch 31RL 012.

What size is a No. 558 bur? The No. 558 has a 1.2 mm head diameter (ISO size 012) on a straight fissure bur head, ISO shape 107 (cylinder, flat end).

What is the difference between a No. 558 and a No. 58? Same shape and size; one is plain-cut and the other crosscut. The No. 558 is crosscut — crosscut cuts faster and clears debris, plain-cut leaves a smoother surface.

What do the letters after No. 558 mean? The 558L (Busch 31L 012) carries a longer cutting head for deeper boxes and taller walls. The 558X is the surgical version: the same cutting head on a 25 mm FG-XL shank for reach when sectioning teeth and roots, with a rounded end.

Carbide or steel? Tungsten carbide for enamel, dentin, composite and amalgam in the clinic; the steel No. 558 is the economical choice for acrylics, plaster and other soft materials in the laboratory.

Are Busch No. 558 burs reusable? Yes. Carbide and steel burs are cleaned, disinfected and sterilized between patients and replaced when they dull; the Bur Sterilization Guide gives the validated steps.

Related resources: US Bur Number Finder · Bur Comparison Chart · Speed Chart · Bur Glossary · Nearby sizes: US No. 556, US No. 557, US No. 559, US No. 560