Spin Me Right Round by Dr. Lori Trost

Prepping a crown with a bur spinning in a high-speed handpiece at nearly 400,000rpm can be daunting. Aside from the challenges of navigating a patient's curious tongue or tight cheek, specific burs are used to reduce tooth structure, create a margin and design a preparation worthy of a final indirect restoration.

Truth be told, dentists often struggle with prepping teeth, even if it is something the dentist does often. This is a reality for most doctors as crown and bridge procedures are the bread and butter in their practices.

With more and more all-ceramic restorations, clinicians need to be aware of material distinctions and minimum depth specifications before the lab technician calls and says there wasn't enough reduction or the margin is in question.

But do we as dentists really understand how to properly use a bur? How can we get the most benefit from the bur design? When does the bur move past its cutting efficiency? Can I reuse a diamond bur? Is there a more straightforward approach when preparing teeth that is predictable while maximizing the cost effectiveness of a diamond bur?

Rigors and demands
Regardless of a single-use or multi-use diamond bur, several factors need to be taken into consideration to better understand a variety of clinical demands placed on a diamond bur's performance.

Apart from an excellent performing high-speed handpiece, the clinical reality is, diamond burs are affected by the rigors of heat, vibration, drag, dehydration and chattering. These effects cause the diamond burs to lose their particles, change shape and become irregular. One of most common issues to be aware of is when the tip—the critical area clinicians rely on to form the margin of the preparation—goes bald. This issue with the instrument can lead to misshapen preparations.

These factors not only reduce the cutting quality and effectiveness, but ultimately create more trauma to the tooth. And, with repeated use, the process dramatically spirals downward causing even more frustration for the dentist.

Practical crown prepping tips
Here are some tips to ensure healthy and efficient crown preparations.

• Measure twice, cut once. Use diamond burs to your advantage. Learn the dimensions of the burs and match those depths to the reduction you need. Now you not only have a cutting tool, but a measuring device as well. Your lab will appreciate your newfound consistency!
• Maximize the bur's cutting performance. Use multi-use burs for quadrant crown preparations and use single-use burs for single crown preps. Discard them once finished! Somehow as clinicians we trip over dollars to pick up pennies. Time is money in dentistry. And in this case, it also laterals over to patient safety.
• Develop a methodical reduction approach. Move around the tooth in a constant direction. Back-and-forth motions often lead to stepping of the margin. Begin with a coarse grit for gross reduction and finalize with a fine grit diamond bur to create a smooth preparation. This has never been more important, especially with the adoption of digital impression capture. Hone it!
• Allow your provisional to be a teacher. When fabricating your provisionals—or if your assistant is—make sure to evaluate for the proper thickness. If the occlusal is thin, the final restoration occlusal table will be too!
• Use copious water when prepping. Water spray is an important variable when preparing a tooth. Not only does it cool the tooth, but it also minimizes clogging of the bur and lubricates the cutting process.

Closing
Using the right tools to do a neat job efficiently is necessary for tricks of the dental trade—with the goal being a healthy, safe and uniformly reduced tooth.

Dentists can agree that no matter what combination of burs or diamond rotary instruments is used to prepare any indirect restoration, they must respect and complement the procedure.

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