Cerec World--User Tips for Efficiency & Profitability

Preparation Powder Optical Impression Computer Design

This installment in the series focuses on the CEREC preparation as the primary foundational element in achieving a quality final restoration.

A typical CEREC tooth preparation for posterior restorations is divided into two main categories:

Inlay/Onlay/Partial Crown Full Crown
The CEREC 3 software requires that the dentist use precisely prepared cavities. Cylindrical instruments should be utilized for preparation of the inner cusp slopes with parallel walls for conservation of tooth structure and well-defined marginal angles. The nature of the optical impression and milling system is such that the dentist needs to take into account special preparation requirements not seen in typical laboratory processed crown and bridge methodology.

The selection of burs utilized for CEREC preparation are an essential element of success as well. Each clinician tends to have their favorite high-speed burs, but we have found that burs that more closely resemble those used in the milling chamber work the best. The first choice for inlay/onlay/partial crown restorations is the straight diamond cylinder with flat end. For the full crown, a round end taper diamond seems to work very well. Of course, a thin flame taper diamond is an excellent instrument for trimming unsupported enamel margins, especially in the proximal box. Our policy is less is best and having to change only a few diamond burs for a CEREC prep is one key to smooth and efficient preparation.

Proper integration of CEREC technology requires a change in the typical operative and crown and bridge restoration techniques. The highly conservative nature of the CEREC inlay/onlay/partial crown preparation methods lends itself to minimally-invasive dentistry. The simple nature of the full crown methods allows dentists to quickly prepare and fabricate CEREC crowns within an hour from start to finish. And if prepared according to the specified guidelines, CEREC restorations rival the fit of any laboratory fabricated ceramic restoration.

Preparation Guidelines:

Flat pulpal floor & vertical walls Undercuts in axial walls are allowed If axial walls are flared, they should not exceed 6 degree divergence Cavosurface margins should be crisp and distinct, not rolled or blunted Axial walls should be straight with no steps or bevels Proximal box axial walls are required to be flared, slightly divergent Thickness of ceramic material must be a minimum of 1.2mm in all dimensions For full crown preps, the margins should be a modified chamfer with an ideal width of 1.2mm and a 6 degree taper of the axial walls.

What are your concerns?
If you have a CEREC question, please send it by fax to 480-598-3450 or send by email to: dwvdds@earthlink.net or carol@dentaltown.com

Douglas Voiers is a reconstructive and aesthetic dentist who has won top honors in the annual Dental Economics' Practice of the Year Awards. He maintains a full time practice in Avon Lake, OH and is currently a clinical instructor for restorative dentistry at the Great Lakes Educational Center in Southfield MI. Douglas recently earned a fellowship in the World Congress of Microdentistry. His other affiliations include the Pankey Institute, the Academy of Computerized Dentistry, the ICOI and the AACD. Douglas can be reached at 440-933-3270 or by email at: dwvdds@earthlink.net.

Mark Morin, DDS, FWCM, graduated from the University of Detroit in 1985 and immediately started his new practice in Southfield, MI. He became one of the first dentists in North America to begin using CEREC I technology. He currently places 10-15 CEREC restorations daily and continues to study CEREC technology extensively in Germany and Switzerland with inventor, Dr. Werner Mormann. Dr. Morin maintains a 6000 sq ft office and ExperDent training. He is one of 10 internationally certified CEREC trainers in North America and has had the distinction of training some of dentistry's most well-know clinicians such as Dr. Rela Christensen and Dr. Howard Farran. Mark can be reached by email at: drmorin@earthlink.net or by calling 248-828-9989. Visit his website at www.drmorin.com.