For more than 15 years, various forms of computer-driven milling devices for restorative dentistry have come and gone. Each has had its share of proponents, but to date, only the CEREC (Sirona) concept has survived in the dental marketplace. It has been estimated that there are about 10,000 dental users of computer-aided design/computer-aided manufacturing, or CAD/CAM, systems, and about 7,000 of those use the CEREC system.1 Also, about 8 million clinical restorations generated by these systems have been placed, more than 4 million of which have been fabricated with the CEREC chairside system.1
The concept of computer-driven milling devices for inlays, onlays, crowns and fixed prostheses is excellent. Its advantages are apparent:
- – the procedure is completed in only one appointment, instead of the two that are needed for conventional laboratory-created restorations;
- – the patient must undergo only one administration of local anesthetic;
- – it involves no laboratory charges;
- – it eliminates the need for a provisional restoration.
Why has computerized restorative dentistry taken so long to be accepted by the profession? I have watched the concept evolve since its inception, and I see several reasons for the slow acceptance.
The original commercially available CEREC device (1986) could mill only inlays. Since very few inlays and onlays are accomplished in the United States, and third-party payers often will not pay for these restorations, practitioners’ interest was minimal. In addition, the device was expensive, and its complexity was formidable to dentists with only minimal computer knowledge. Finally, the esthetic result of the inlays was moderate at best.
The second generation of the CEREC device (1994) was a major improvement. This device could make inlays, onlays and crowns, and this new treatment diversity increased interest in the system. However, the other disadvantages were still present.
The third generation of the CEREC device, recently released, again increased in overall acceptance because of its improved computer technology. The remaining major impediment is its high cost, which appears to be well beyond the means of many dentists. However, experienced CEREC users state that the cost of the CEREC system can be offset rapidly by elimination of laboratory costs.2
At this time, there are several computer-milling devices for restorative dentistry evolving around the world. They perform different functions or steps in the restorative procedure, ranging from construction of only copings for crowns to construction of entire restorations. In this article, I discuss the viability of the concept, the current limitations of computerized restorative dentistry, and potential future uses for computerized restorative dentistry.
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VIABILITY OF THE COMPUTERIZED RESTORATIVE DENTISTRY CONCEPT
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Can a typical general dental practitioner cope with the cost of a CAD/CAM device? There are financial plans available that spread the cost of the CEREC device over a long period, or lease plans that make monthly payments tolerable. If such financial plans are used, the cost of the device becomes less objectionable. However, a practitioner must be highly motivated to purchase a computerized milling device. Before the CEREC could make crowns, its cost was not justifiable to most dentists. Now that it can make crowns, dentists who have become proficient with the concept claim that they have found computerized restorative dentistry to be both clinically and financially sound. However, they admit that becoming proficient enough in use of the system to be financially successful with it requires significant time. For dentists who have great interest in the concept and ability with computers, computerized restorative dentistry can be financially acceptable.
Since only single crowns can be made with the device at this time, can computerized dentistry accomplish enough restorative dentistry to be used routinely? I have estimated, from my experiences on the dental lecture circuit, that about 80 percent of the fixed prosthodontic procedures accomplished by a typical restorative dentist are single crowns. The majority of these crowns are for posterior teeth. The main usefulness of computerized dentistry has been for posterior teeth, because of the monochromatic nature of most of the ceramic or polymer blocks from which the crowns are ground. Nevertheless, I can conclude that a practitioner accomplishing an average or above-average quantity of fixed prosthodontic procedures would find himself or herself using a CAD/CAM system routinely.
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LIMITATIONS OF COMPUTERIZED RESTORATIVE DENTISTRY
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Cost of the equipment.
Cost of the equipment still is a significant limitation when individual dentists attempt to purchase the entire system and implement it in their solo practices. I will offer an alternative later.
Color of finished restorations.
The color of finished restorations still is a challenge, because of the monochromatic character of most of the blocks from which restorations are milled. New methods of producing multicolor blocks are being introduced, which will help resolve the situation. However, until the multicolor block concept is mature, the only alternative for producing normal tooth coloration is placing superficial stains on the outside of the crowns. This procedure can be done in the office by dentists or assistants. The longevity of this coloration is limited, because of the well-known dissolution of the stains, as well as the wear of the stains during service. The current method of superficial staining of crowns does not produce an adequate esthetic result for most anterior tooth situations. However, while firing conventional ceramic on the surface of the computer-milled restoration is feasible, this procedure requires both the services of a laboratory technician and more time and effort.
Staff training.
A well-educated, motivated staff is essential for success in computerized restorative dentistry. To make this concept work well, many clinicians who have made the computerized restorative concept financially viable for their practices have trained staff members to make the restorations after the dentist has completed the tooth preparations. The dentist then returns to seat the restorations after a dental assistant or dental hygienist has made the restoration. Other modes of practice can be adapted to computerized restorative dentistry, but involvement of staff is necessary for adapting computer restorative dentistry to active multioperatory practices.
Severely broken-down teeth.
Very broken-down teeth are a challenge when treated with computerized restorative dentistry. Most of these teeth have gingival margin extensions that are deeply subgingival. As a result, making digital pictures of the tooth preparations to direct the computer and the milling device may be difficult. In such cases, gingival retraction methods, not unlike those used in typical fixed prosthodontic procedures, are necessary.
Single-unit vs. multiunit restorations.
Computerized restorative dentistry accomplished in private dental offices still is limited to single units; however, multiunit restorations are coming. This limitation is a significant one, and its solution needs immediate attention.
Time requirements.
The time involved to fit, polish and seat a computerized restoration is longer than that involved in most restorations made by a typical dental laboratory. With experience come more speed and expertise, but these changes require time and effort.
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POTENTIAL FUTURE USES FOR COMPUTERIZED RESTORATIVE DENTISTRY
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Copings for crowns.
The most significant use of computerized restorative dentistry today is in making the internal core for restorations such as the Nobel Biocare restoration, Procera. This concept is well-accepted and is being used worldwide. I predict that computer-directed milling of copings will continue to be used and refined, and that it will continue to be a major restorative concept for the future.
Crowns and fixed pros-theses milled in private offices.
I predict that in-office use of computerized restorative dentistry will continue to grow, especially in the in-office production of crowns and fixed prostheses, but it will be limited because of both the cost and the difficulty of finding well-educated, responsible in-office staff members to take over part of the procedure.
Multioffice users.
If several offices form a team using one centrally located computer-milling device, the cost of the concept can be shared, and the personnel can obtain enough experience to become proficient.
Ownership by dental laboratories.
In areas with a significant population of dentists, laboratories could own the computerized milling equipment, and nearby dentists could telephone the tooth preparation measurement information to the laboratory. The restoration could be milled in the laboratory and delivered to the dentist within a short time. This concept is becoming more popular.3
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SUMMARY
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Computerized systems for accomplishing restorative dentistry have made a significant impact on dentistry worldwide. Of such systems, only the CEREC system has remained on the market for a period of years. Use of computerized restorative dentistry in private offices is growing, and other methods of using this concept in dentistry are continuing to improve. I am confident that computerized restorative dentistry will grow and prosper, and that it will become a viable treatment entity for the profession in the future.
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VIABILITY OF THE COMPUTERIZED...
LIMITATIONS OF COMPUTERIZED...
