The 245 Carbide Bur: Why It's Still the Operative Workhorse
Ask a room of general dentists which carbide they would keep if they could only keep one, and most of the room says the same number.
The 245 has outlasted amalgam's peak, the shift to composite, and a dozen "next-generation" operative burs. It is still in nearly every operative tray. Not out of habit, but because its shape does three jobs at once that most burs split across two or three instruments.
Here is what the 245 actually is, why the shape works, where it fits against the 330, 557, and 1158, and how to get more out of it.
What a 245 bur is
The 245 is a tungsten carbide operative bur with an elongated pear-shaped head: narrow at the tip, slightly wider toward the shank, with rounded corners. It runs on an FG shank in a high-speed handpiece.
The Taft 245 head measures 0.9 mm by 2.5 mm, on a 19.0 mm FG shank. Head length varies a little between manufacturers, and many 245s run closer to 3 mm, so know the spec on the one in your block. That number matters, as you will see below.
Why the shape does so much work
Every part of the 245's head geometry lines up with what a conservative Class I or Class II prep needs.
- Slight taper toward the tip. Held parallel to the long axis of the tooth, the 245 cuts walls that converge slightly toward the occlusal. For amalgam, that convergence is built-in retention form. You do not have to angle the bur to get it.
- Rounded corners. The internal line angles come out rounded instead of sharp. That means less stress concentration in the tooth and in the restoration, and a floor that composite adapts to more easily.
- A known head length. The head is a built-in ruler. Sink it to its full length and you know your pulpal depth without a probe. Sink it halfway and you know that too.
- A narrow tip. It enters a pit or fissure without widening the outline, which keeps preps conservative from the first cut.
Access, outline, depth, and internal form, all from one instrument. That is why the 245 stays in the handpiece for most of a routine prep.
What the 245 is used for
- Class I preps: occlusal access and outline, following the fissures.
- Class II preps: the occlusal outline, then the proximal ditch along the dentinoenamel junction. The full sequence is in our Class I and Class II cavity prep guide.
- Removing old restorations: cutting out existing amalgam or composite, where a carbide's shearing action beats a diamond, which loads up on metal.
- Retention features: the rounded corners and small head make it useful for refining internal form.
What it is not for: caries excavation near the pulp (a round carbide at slow speed gives better feel), crown prep axial reduction (a diamond's job), or cutting zirconia (carbide blades cannot handle it).
245 vs 330 vs 557 vs 1158
These four sit side by side in most operative blocks. Here is how they divide the work, using Taft head specs.
| Bur | Shape | Head (Taft) | Floor and line angles | Best for |
|---|---|---|---|---|
| 245 | Elongated pear | 0.9 × 2.5 mm | Rounded | Class I and II outline, depth gauging, removing old restorations |
| 330 | Small pear | 0.8 × 1.9 mm | Rounded | Conservative composite preps, narrow fissures, small lesions |
| 557 | Straight fissure, crosscut | 1.0 × 4.2 mm | Flat, defined | Flat floors, defined walls, sectioning, crown removal through metal |
| 1158 | Dome fissure | 1.2 × 4.2 mm | Rounded, wider | Class II boxes with a rounded internal floor |
245 or 330? The 330 is the smaller, more conservative choice for minimal composite preps. The 245 is longer and slightly wider, better for average-size lesions and for gauging depth. Many clinicians keep both and choose per lesion.
245 or 557? The 557's crosscut blades and flat end make it the faster cutter for sectioning, cutting through metal crowns, and flat-floored amalgam preps. The 245 gives rounded internal form. Different jobs, not substitutes.
Every one of these numbers, with head dimensions and photos, is in our bur shape and number chart.
Getting more out of a 245
- Keep it parallel to the long axis. The shape only builds correct wall form if the shank is parallel. Tilt it and you flare one wall and undercut the other.
- Use the head as a gauge on purpose. Before the first case with a new pack, confirm the head length. Then read pulpal depth off it every time.
- Use water at high speed. Carbides run cooler than diamonds, but high-speed cutting still needs coolant.
- Let the blades cut. Light, intermittent pressure. If you are leaning on it, something is wrong with the bur, not your hand.
When a 245 is done
Carbides do not wear like diamonds. They do not lose grit. Their blade edges round over, and a rounded blade stops shearing and starts burnishing. It skips, chatters, and polishes dentin instead of cutting it.
The 245 does most of the work on most routine preps, which makes it one of the fastest-wearing carbides in the block. Retire it when:
- You are pressing harder to get the same cut
- The blade edges look shiny instead of matte under the light
- It chatters or skips where it used to cut smoothly
- The shank is bent or it wobbles in the handpiece
Your hand compensates before you notice the change. We call that Bur Drift, and it is covered in signs your dental bur is dull.
Stock it like the workhorse it is
Because the 245 does so much of the operative work, it should be the carbide you never run out of. Give it its own reorder rhythm, and keep the 330, 557, and 1158 next to it so every Class I and II has the right instrument at each step.
Taft carbide burs, including the 245, 330, 557, 1158, and round carbides, are $29.95 for a box of 10, FG shank, direct with no rep and no minimums. Subscribe & Save on the product page puts your most-used numbers on a schedule. Want the full sequence in one box? The Cavity Prep kit (FG-103) is built for access and caries removal. Questions: 513-580-8414.
Common questions
What is a 245 bur used for?
The 245 is a pear-shaped carbide used mainly for Class I and Class II cavity preparation: occlusal access, outline form, the proximal ditch, and removing old amalgam or composite. Its shape builds slightly convergent walls and rounded internal line angles when held parallel to the long axis of the tooth.
What size is a 245 bur?
It varies slightly by manufacturer. The Taft 245 head is 0.9 mm wide and 2.5 mm long on a 19.0 mm FG shank. Many 245s have a head length closer to 3 mm, so check your supplier's spec if you use the head as a depth gauge.
What is the difference between a 245 and a 330 bur?
Both are pear-shaped carbides. The 330 is smaller, about 0.8 mm by 1.9 mm on the Taft version, and is used for more conservative preps and narrow fissures. The 245 is longer and slightly wider, suited to average-size lesions and to gauging pulpal depth.
What is the difference between a 245 and a 557 bur?
The 245 is a pear shape with rounded corners that leaves rounded internal line angles. The 557 is a straight fissure crosscut with a flat end that leaves flat floors and defined walls, and its crosscut blades cut faster through metal and during sectioning.
Is a 245 bur carbide or diamond?
The 245 is a tungsten carbide bur. It cuts by shearing with blades rather than abrading with grit, which gives better tactile feedback in dentin and makes it effective on amalgam and composite.
Professional Use Only. Licensed Dental Professionals. General information only. Preparation design varies by restorative material and case. Follow manufacturer instructions and your clinical judgment.