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The Future?

The cast gold alloy restorative concept, introduced into dentistry about 100 years ago, has served the profession and the public well for many years. However, porcelain fused to metal (PFM), introduced into the profession about 50 years ago, has become the mainstay of indirect dental restorations in the United States. Glidewell Laboratories (Newport Beach, Calif.), one of the largest dental laboratories in the United States, reports that currently about 61 percent of all crowns and fixed prostheses are PFM restorations (J. Shuck, oral communication, April 2007). More than 20 years ago, in-office computer-aided design/computer-aided manufacturing (CAD/CAM) of dental restorations was introduced as an alternative to the lost-wax metal casting concept for fabrication of indirect restorations.

Although becoming more popular now, the CAD/CAM concept has been relatively slow in being integrated into practice. The CEREC device (Sirona Dental Systems GmbH, Bensheim, Germany) has dominated the in-office milling concept as the only commercially available in-office machine. Sirona estimates that there are about 22,000 CEREC devices in offices around the world, including 8,000 in the United States (E. Hansen, oral communication, November 2007).

Approximately 10 years before the CAD/CAM milling concept was introduced, the esthetic dentistry movement toward tooth-colored direct and indirect restorations began growing rapidly. Emphasis on esthetic dentistry and the CAD/CAM concept has reduced use of the metal casting procedure, whether as metal alone or as PFM.

The CEREC in-office milling concept has evolved from a rudimentary, difficult-to-understand, difficult-to-use device to a sophisticated, relatively easy-to-use machine. Some purchasers of the CEREC device have found in-office milling to be indispensable, while others have not found it to be appropriate for their practices. Nevertheless, after more than 20 years of use in the profession, the concept has achieved maturity, and I anticipate its continued acceptance by the profession.

In this column, I will compare the clinical acceptability of CAD/CAM–milled restorations with handmade laboratory restorations, make observations on the practice management concepts related to the in-office use of CAD/CAM, evaluate the potential influence of another in-office CAD/CAM device now being introduced to the profession, and offer my thoughts on the future of this technology in the profession.

	CLINICALLY MILLED RESTORATIONS VERSUS LABORATORY HANDMADE RESTORATIONS

TOP CLINICALLY MILLED RESTORATIONS... PRACTICE MANAGEMENT CONCEPTS FOR... A NEW DEVICE THE FUTURE REFERENCES

 
Many studies^1–18 have compared in-office, computer-driven, machine-milled restorations with laboratory handmade restorations relative to fit of restorations, esthetic results, longevity and other factors.

The fit of CAD/CAM restorations has been well-documented to be as good as or better than that of restorations fabricated by hand.^19–22 However, the responsibility for monitoring the acceptability of fit of in-office CAD/CAM restorations falls solely to the dentist and the clinical assistant, while the laboratory technician, the dentist and clinical assistants all observe, critique and accept or reject the fit of laboratory handmade restorations. As with any other area of dentistry, the clinical quality of CAD/CAM–milled restorations varies significantly, dependent entirely on the quality standards of the clinician. When visiting clinical offices, I have seen CEREC restorations fit impeccably, and I have seen ill-fitting pieces of ceramic or polymer sitting in a sea of resin cement. The CAD/CAM concept does not ensure quality. The dentist still must take the time to ensure that CAD/CAM–fabricated restorations have acceptable quality characteristics.

The esthetic acceptability of these restorations varies according to the technique used.¹ The single color of a restoration milled from a solid monocolor block is adequate for some applications but not acceptable for others. When blended colors are necessary to satisfy the esthetic needs of the clinical situation, one of two techniques can accommodate the need. In the first, layered ceramic is fired on the external surface of the monocolor milled restoration, providing the desired esthetic result. (Of course, the extra time and effort required to accomplish the layering technique requires a higher fee.) In the second, a multicolor milling block is used. If the location of the needed color change in the restoration is planned well and the block is milled to meet the color need, this technique can provide a near-optimum color match for some clinical situations. Color match of these restorations varies from poor to excellent, depending on the technique used and the clinician’s esthetic ability and sensitivity. There is controversy as to whether the average CAD/CAM restoration is as acceptable, from an esthetic standpoint, as the average handmade laboratory indirect restoration.

Many clinical studies^1–17 have observed the service potential of in-office computer-driven and -milled indirect restorations. The reports vary significantly. My own observations and interpretation of the available research lead me to conclude that these restorations serve no better or worse than do their conventional counterparts, and that their clinical longevity is highly operator-dependent. I do not question the ability of CAD/CAM restorations to serve well if proven principles of restorative dentistry are observed.

	PRACTICE MANAGEMENT CONCEPTS FOR IN-OFFICE CAD/CAM

TOP CLINICALLY MILLED RESTORATIONS... PRACTICE MANAGEMENT CONCEPTS FOR... A NEW DEVICE THE FUTURE REFERENCES

 
Practice management principles applied when using in-office CAD/CAM differ from those used with conventional restorations. Currently, Patterson Dental (St. Paul, Minn.) sells the CEREC device for about $100,000, depending on the model. The lease payment on the device is $2,000 or more per month (Brandon Bodily, Patterson Dental, oral communication, November 2007). A new device, to be discussed below, costs about the same when all factors are considered. Each company has different financial policies on warranties, upgrades, length of lease period and so forth, so prices are not directly comparable. Blocks from which to mill restorations come from the same manufacturers and cost about $18 each, but the clinician is saving the cost of impression and provisional materials, as well as the cost of a second appointment, to offset the additional expenses.

Glidewell Laboratories’ average laboratory fee for a conventional PFM restoration is about $140 (J. Shuck, oral communication, November 2007). Using this information, I calculate that a clinician using CAD/CAM must make about 16 restorations per month, or about one every practice day, for the cumulative value of the replaced laboratory bill to equal the lease payment and the cost of the blocks. Any restorations accomplished beyond 16 per month have the equivalency of no laboratory bill. When a clinician becomes proficient with the device and integrates it into the practice routine, the concept can be financially successful.

If the dentist stays with the patient for the entire CAD/CAM clinical procedure, the time involvement is about 45 to 60 minutes for one restoration. If the majority of the procedure is delegated to a competent staff member, where legal, the dentist’s time involvement can be reduced by at least one-half. I suggest delegating the entire procedure except the tooth preparation and seating the restoration, where legal.

	A NEW DEVICE

TOP CLINICALLY MILLED RESTORATIONS... PRACTICE MANAGEMENT CONCEPTS FOR... A NEW DEVICE THE FUTURE REFERENCES

 
For more than two decades, the CEREC device has not had serious competition. The introduction of the E4D in-office CAD/CAM device (D4D Technologies, Richardson, Texas; marketed by Sullivan Schein, West Allis, Wis.) marks the entry of long-awaited competition. Is the new device better or worse than the CEREC? That decision is yet to be made, as controlled clinical studies are conducted and reported.

In my opinion, having two companies competing will stimulate both companies to further develop their devices and will motivate allied companies producing restorative materials to continually improve their products. I welcome this competition, as do the leaders and employees of both companies (S. Anderson, president, Patterson Dental, oral communication, November 2007; B. Heymann, chairman and chief executive officer, D4D Technologies, oral communication, Nov. 28, 2007). The in-office CAD/CAM concept will be advanced by this competition.

	THE FUTURE

TOP CLINICALLY MILLED RESTORATIONS... PRACTICE MANAGEMENT CONCEPTS FOR... A NEW DEVICE THE FUTURE REFERENCES

 
In-office CAD/CAM is here. Many practitioners love the concept and use the CEREC device routinely, and I expect the same soon to become true of the E4D device. There is no question that most patients prefer the CAD/CAM one-appointment concept to the conventional two-appointment (preparation and seating) approach of the conventional indirect procedure.

Will all dentists gradually come to use CAD/CAM in their offices? After years of observing dentists in hundreds of practice environments, I believe that many practitioners will incorporate in-office CAD/CAM into their practices, but that many also will elect to remain with conventional restorative procedures. Although there are some dentists who enjoy creating indirect restorations in their offices and who do not object to taking the time to modify occlusion, contact areas and other restoration characteristics, many others desire to delegate those responsibilities to laboratory technicians. It has been my observation that many dentists prefer to make the tooth preparation, make an impression, send the impression (either conventional or digital) to a laboratory and receive the final product from the laboratory in finished form, requiring little or no clinical modification at the seating appointment.

However, thousands of dentists use and enjoy the CAD/CAM concept. The restorations fit as well and serve as well as conventionally made restorations. Much of the CAD/CAM procedure can be delegated to competent staff members, where legal. A new product, E4D, will provide competition for the now-proven CEREC device. I predict that the future will see continued development of the concept and the devices, moderate but consistent growth of the concept, and continuing and growing acceptance.

	FOOTNOTES

The views expressed are those of the author and do not necessarily reflect the opinions or official policies of the American Dental Association.

	REFERENCES

TOP CLINICALLY MILLED RESTORATIONS... PRACTICE MANAGEMENT CONCEPTS FOR... A NEW DEVICE THE FUTURE REFERENCES

 

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