Bur Numbers Decoded: 330, 557, 245 and Busch's Best-Selling Patterns

Ask any US dental team which burs they reorder most, and three numbers come up again and again: 330, 557, and 245. These US bur numbers aren't arbitrary — each one maps to a specific cutting-edge shape with a defined clinical role.

The 557 bur anchors most cavity and crown-prep kits thanks to its straight fissure, crosscut design, while the 330 pear bur handles excavation and the 245 torpedo bur finishes and contours restorations.

This reference guide decodes what each number means, compares Busch's best-selling patterns side by side, and links to the specific figures worth stocking. Browse the full Most Popular Burs in US Market collection for the complete lineup.

What US Bur Numbers Actually Mean

US bur numbers trace back to a numbering convention established decades ago by American manufacturers and still used for ordering shorthand across US practices, even though most burs are now manufactured to ISO/FDI shank and length standards internationally. A single US number, like 557 or 330, can correspond to several Busch product figures once shank type (FG, HP, RA) and grit or flute pattern are factored in. Knowing the US number lets a team order the right cutting geometry without needing to memorize the equivalent Busch figure for every shank variant. This guide covers the three most-searched US bur numbers together with a comparison table so your team can order confidently regardless of which shank format you need.

557 Bur: The Straight Fissure Standard

The 557 bur is a straight-sided cylinder (fissure) shape with a flat end, designed for creating flat pulpal and axial walls during crown, bridge, and inlay preparation. Busch produces this pattern as Figure 31 in carbide, with crosscut flutes that reduce clogging and chatter compared with plain-cut equivalents. It's available in FG for high-speed handpieces and HP for slow-speed use, plus long (31L) and extra-long (31RL) variants for deeper preparations. Best for: flat-floored crown and bridge preparation — the Busch No. 31 010 Crosscut FG is the standard FG figure most US labs reorder.

330 Bur: The Pear-Shaped Prep Bur

The 330 bur uses a pear shape — narrower at the neck, wider at the tip — that lets it cut an undercut, retentive cavity outline in a single pass. Busch manufactures this pattern as Figure 7 in carbide, sized to match the traditional 330 dimensions US clinicians expect for Class I and Class II amalgam and composite preparation. Best for: retentive cavity outline form and caries excavation — the Busch No. 7 008 FG pear bur is the closest match to the classic 330 geometry.

245 Bur: Torpedo Finishing and Contouring

The 245 bur is a tapered, torpedo-shaped pattern used for finishing composite margins, contouring occlusal anatomy, and refining crown preparations after the bulk of the cutting is done. Busch's Figure 245 carbide finishing bur carries fine flutes that leave a smoother surface than a coarser cutting bur, reducing polishing time. Best for: composite finishing and margin refinement — the Busch No. 245 014 FG torpedo bur is built for this exact step. For slow-speed caries excavation, many of the same teams pair it with a round rosehead pattern like the Busch No. 1SXM 014 SXM-Cut HP.

Comparing Busch's Best-Selling Bur Patterns

FAQs

What shank type does the 557 bur come in?
Busch's 557 pattern (Figure 31) is available in FG for high-speed handpieces and HP for slow-speed handpieces, plus long (31L) and extra-long (31RL) versions for deeper access.

Is a 330 bur the same as a pear bur?
Yes. The US No. 330 designation refers to a pear-shaped carbide bur; Busch manufactures this shape as Figure 7, sized to match traditional 330 dimensions.

When should I use a 245 bur instead of a coarser finishing bur?
The 245 torpedo pattern is best reserved for the finishing and contouring stage, after bulk reduction, since its fine flutes are designed to refine margins rather than remove material quickly.

Can the 557 bur be used for cavity preparation as well as crown prep?
Yes. Its flat-ended cylinder shape works for both flat-floored cavity preparations and crown or bridge margin prep, which is part of why it's one of the most reordered patterns in the US market.

How many times can a carbide bur like the 330 or 557 be reused?
Most practices treat carbide burs as limited-use or single-patient-use instruments; inspect flutes for wear, chipping, or dulling after each use and retire any bur showing reduced cutting efficiency.

What other patterns pair well with 330, 557, and 245 in a standard kit?
Round excavation burs such as the 1SXM series and additional cylinder or torpedo diamonds are common companions, rounding out a kit for prep, excavation, and finishing in one system.

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