US No. 58 Busch Carbide Straight Fissure (Cylinder) Bur | Busch No. 21 012 – RA | Pack of 6

Busch No. 21 012 – RA (US No. 58) is a 1.2 mm (ISO 012) flat-end carbide cylinder fissure bur on a latch-type right-angle (RA) shank, sold in packs of 6. It runs in slow-speed contra-angle handpieces and is the low-speed alternative to the 21 012 FG; both are made in Germany by Busch & Co. GmbH.

Why choose the RA version

At low speed in a latch contra-angle the 1.2 mm cylinder is typically used to finish and refine preparations — establishing flat pulpal floors, squaring walls, and excavating dentine where the reduced speed gives better tactile control and less heat than a turbine. The RA shank fits standard slow-speed handpieces; move to the FG version of the No. 58 for high-speed enamel cutting.

Also available: No. 21 010 – FG, No. 21 010 – RA, No. 21 012 – FG, No. 21 016 – FG, No. 21 016 – HP, No. 21R 014 – HP, No. 21R 014 – FG.

Product Classification

This carbide cylinder fissure dental bur is classified under the following ISO standard:

• ISO: 500 204 107 006 012
• US No.: 58
• Shape: Cylinder Flat (RA shank)
• Material: Carbide
• Pack Size: 6 burs per pack

Key Features

• Carbide construction for superior hardness and wear resistance
• Cylinder flat geometry provides controlled, flat-floored cavity preparation
• RA (Right Angle / Latch-type) shank for compatibility with standard slow-speed handpieces
• Engineered and manufactured in Germany to exacting quality standards
• Consistent cutting efficiency across repeated clinical use

Instrument Dimensions

Per ISO 6360, the size number is the maximum head diameter in tenths of a millimeter. See our Busch Bur Size Chart for the full size conversion table, shank codes, and color ring guide.

Applications

The carbide cylinder fissure dental bur is well-suited for the following clinical procedures:

Cavity/Fissure Preparation — Opening, extending and shaping cavities and fissures with controlled removal of enamel and dentin.

Its cylinder flat design makes it an ideal choice for accessing and excavating fissures, establishing flat pulpal floors, and preparing Class I and Class II cavities with precision and efficiency. The RA latch-type shank ensures secure engagement with standard slow-speed contra-angle handpieces, making integration into existing clinical workflows straightforward.

FAQ

What shank type does this bur use? This bur features an RA (latch-type) shank, compatible with standard slow-speed contra-angle handpieces.

How many burs are included per pack? Each pack contains 6 burs.

What is the ISO classification for this carbide cylinder fissure dental bur? The ISO classification is 500 204 107 006 012.

Where is this bur manufactured? This bur is engineered and manufactured in Germany to exacting quality standards.

Compare With

Manufacturer literature: Busch catalogs and product brochures for this line are available in our Busch Burs Catalog Library.