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Inside Dentistry

April 2006, Volume 2, Issue 3
Published by AEGIS Communications


CAD/CAM

Eugene L. Antenucci, DDS, FAGD

Dental education was arguably much simpler in days past. It was only 10 years ago when the major concerns for dental practitioners were dental anatomy and physiology, materials science, and perfecting dental operative techniques. It was challenging enough to master the techniques of achieving the perfect margin while simultaneously learning to become physicians of the oral cavity as well as small business owners. Today, however, dentistry is undergoing a rapid revolution as it incorporates technology at a dizzying pace. Not only are the dentists of 2006 physicians of the oral cavity, master technicians, materials scientists, and business people, they are finding themselves in the position of needing to understand and master advanced aspects of computer engineering.

What Is CAD/CAM?

The term CAD/CAM is an acronym for computer-aided design (CAD) and computer-aided manufacturing (CAM). In industry, CAD/CAM refers to the process of using computer systems to create, design, and manufacture many different types of products. The term CAD/CAM implies that a user can utilize a particular system for both designing their desired product and for controlling the manufacturing process. The CAD component produces the design while the CAM component of the system controls the machines that construct the intended product.

During the 1950s, industry readily began adopting tools that were dependent on the systematic control of numbers and letters that could repeatedly be used to manufacture shapes of varying dimension and complexity. The aircraft industry made use of such technology to accurately and repeatedly produce its components. As digital technologies were introduced and rapidly refined in the 1960s, engineers developed sophisticated tools, which offered greater degrees of automation to manufacturing processes. CAD software development led to numerous applications, such as AutoCad® (Autodesk, Inc, San Rafael, CA), which provided engineers, designers, and manufacturers a sophisticated set of tools and systems to design, develop, and manufacture a wide variety of products that span nearly every industry. The rudimentary systems of the 1960s have now become so advanced that, combined with the power, small size, and relatively low-cost of computers, the technology is not only accessible, but is also usable by individuals without a design or engineering background.

In dentistry today, CAD/CAM are mature technologies that have become integral modalities both clinically and in the dental laboratory. Dental CAD/CAM technologies that were in their infancy 20 years ago and that represented the dreams of their visionary proponents, have now gained widespread recognition for their clinical utility.

The first commercially available dental CAD/CAM system was the CEREC® system (Sirona Dental Systems, Charlotte, NC), which was developed in 1980 at the University of Zurich by Mormann and Brandestini. The first dental patient was treated using the CEREC method and a block composed of VITA® porcelain (Vident, Brea, CA) in 1985 at the University of Zurich. In 1987, Siemens AG (Munich, Germany), which had acquired the license to market and develop CEREC, introduced CEREC®1, with indications for single- and dual-surface inlays with VITA porcelain blocks.

Although CEREC may be the most readily known CAD/CAM system in dentistry, many other CAD and CAD/CAM systems are in everyday use bothin the United States and worldwide. CAD/CAM systems can be divided into two categories. The first category includes systems that are primarily clinical, and intended for use by the dentist and staff to design and deliver restorations. CEREC® 3D (Sirona Dental Systems) is at the forefront of this category (Figure 1). The second category is laboratory-based CAD/CAM systems, which have witnessed a great degree of growth and development over the past decade. This category includes systems such as Procera® (Nobel BioCare, Yorba Linda, CA), Everest® (Kavo Dental, Lake Zurich, IL), Lava™ (3M ESPE, St. Paul, MN), Precident System (DCS Dental, Allschwil, Germany), Cercon® Smart Ceramic System (Dentsply Ceramco, York, PA), Hint-ELs® DentaCAD Systeme (Hint-ELS, Griesheim. Germany), Denzir™ (Decim AB, Skellefteå, Sweden), and the CEREC® inLab (Sirona Dental Systems). The only technology currently available with both a clinical and a laboratory component is CEREC 3D combined with CEREC inLab.

A variation of CAD/CAM technology is evident in other fields in dentistry.In orthodontics, Invisalign® (Align Technology, Inc, Santa Clara, CA), OrthoClear™ (OrthoClear, Inc, San Francisco, CA), and emodel™ (GeoDigm Corporation, Chanhassen, MN) are all produced through CAD/CAM systems. In addition, several implant manufacturers along with other companies are using CAD or CAD/CAM to plan implant placement, guide implant placement, and manufacture both abutments and restorations.

CAD/CAM systems provide many clinical advantages for practitioners and many advantages in the dental laboratory for the technicians and their clients. Ultimately, the patients receiving care also benefit. Clinical systems such as CEREC uniquely allow for single-visit restorations. Patients avoid temporization, tray impressions, and additional visits, and can expect highly esthetic, well-fitting, long-lasting, and metal-free restorations. Practice efficiency and productivity is also greatly increased. Dentists can completely control the process of tooth restoration from diagnosis through preparation, optical impressioning, design, esthetics, and delivery. Laboratory-based systems allow for increased automation of laboratory procedures, with the potential of providing consistently high levels of accuracy of fit, increased quality control, and decreased fabrication time. Managing cross contamination and infection control is simplified or completely eliminated. The obtainable esthetic results are excellent and rival all previously used laboratory processes.

CAD/CAM Materials for Restorative Dentistry

A wide variety of materials are available for use with CAD/CAM restorative systems, including ceramic, composite, and titanium; however, the majority of the systems are used to produce ceramic dental restorations.

The CEREC 3D clinical system can fabricate inlays, onlays, veneers, and crowns from three different materials. IPS Procad® (now IPS e.max® CAD) (Ivoclar Vivadent, Amherst, NY) is made of leucite-reinforced porcelain supplied in premanufactured blocks ranging in size from 8 mm to 14 mm (Figure 2 and Figure 3). The porcelain is essentially identical in formulation to IPS Empress®2 (Ivoclar Vivadent). It exhibits excellent wear characteristics and physical properties compared with natural tooth structure. The blocks themselves are monochromatic, and, until recently, have been designed to match the Chromascop® Shade Guide (Ivoclar Vivadent). New shade designations comparable to the commonly used A-D system will make IPS Procad blocks compatible with other popular shade systems. This porcelain is highly translucent, and is supplied in low and high translucency versions of each shade. Restorations created with IPS Procad can be fired in a porcelain oven if staining and glazing or cutbacks and additions are desired for enhanced esthetics.

VITAblocs® Mark II (Vident) ceramic blocks are feldspathic porcelain blocks with excellent physical properties. They are supplied in a variety of sizes, including a veneer block, and match the Vitapan shade system (Vident) with both low- and high-translucency shades available. In addition to monochromatic blocks, they offer several shades of tricolored or TriLuxe blocks (Vident), which exhibit a shade gradation from cervical to occlusal/incisal. As with IPS Procad, Vitabloc Mark II blocks can be fired in an oven for characterization and glazing or porcelain addition. Vitabloc Mark II blocks are indicated for inlays, onlays, single-unit crowns, and veneers.

Paradigm™ MZ100 blocks (3M/ESPE) are nonceramic composite blocks, which are available for CEREC 3D. Paradigm blocks are essentially Z100™ composite (3M/ESPE) formulated for use with CEREC. They have excellent physical properties, and are provided with an adequate range of Vita-based shades. Paradigm blocks are provided in two sizes, and can be used to create restorations up to 14 mm. Unlike the ceramic blocks, they cannot be fired in an oven for material addition or external characterization, staining, or glazing. Shade characterization is accomplished by internal color modification with resin shades.

The laboratory-based systems use a variety of materials. Procera for anterior and posterior crown copings is fabricated from aluminum oxide. In-Ceram® Alumina (Vident) (aluminum oxide) is used with the CEREC inLab and DCS Precident in the fabrication of anterior crown and bridge copings. In-Ceram® Spinell (Vident) (magnesium oxide) is used with CEREC inLab for anterior crown copings. In-Ceram® Zirconia (Vident) (zirconium oxide) is used with CEREC inLab and DCS Precident to fabricate posterior crown copings and bridge frameworks. Partially sintered zirconia is used with DCS Precident, Lava, Procera, Everest, and Cercon for both crown and bridge copings. Fully sintered zirconia is used with DCS Precident and Kavo Everest for crown and bridge copings. Some metals, such as gold and titanium, can be milled by some systems.

Much of the excitement that has been generated by the laboratory-based systems centers on the relative strength of the metal-free ceramic systems. Zirconia, whether it is fully sintered, presintered, or requires sintering, is an extremely strong material, which can replace metal for posterior crowns and small-unit bridges. Copings that are milled from zirconium can be laminated with a variety of low-fusing porcelains, allowing for excellent esthetics, material strength, and physical properties.

Clinical Systems

CEREC 3D is currently the only clinical chairside system in use. That is, it is the only system currently available that dentists can use to make single-unit, full- and partial-coverage ceramic restorations for both anterior and posterior teeth. From start to finish, most restorations are completed in less than 90 minutes. The CEREC system itself is celebrating its 20th year of clinical use in 2006. As previously described, CEREC 3D can mill blocks of IPS Procad leucite porcelain, Vita Mark II feldspathic porcelain, and Paradigm composite Z100 blocks. Dentists can aquire an optical image of the tooth prepared for an inlay, onlay, crown, or veneer, design the restoration chairside, mill the restoration from the desired material, characterize and glaze if desired, and seat the restoration in a single visit. The benefits to the patient are numerous, including no provisionals are needed, intraoral impression materials are not required, the esthetics that can be achieved are excellent, and the restorations have performed extremely well over a long period of time in relation to other commonly used restorative materials. From the dentist’s perspective, the benefits also are numerous. The fact that restorations can be accomplished in a single visit saves the practice significant time and money. Laboratory costs are also dramatically reduced; in fact, CEREC 3D essentially becomes an in-office laboratory, with the potential of fabricating the majority of posterior single-unit restorations in the practice. With additional training and equipment (training in characterization, staining, and glazing, along with a vacuum porcelain furnace), CEREC 3D can produce highly esthetic anterior crowns and porcelain laminate veneers.

Laboratory Systems

CEREC inLab is the laboratory version of CEREC 3D (Figure 4). This system allows dental laboratory technicians to fabricate dies and copings from a variety of materials, and individually layer all-ceramic restorations. The optical impressions are derived from an optical scan of the dies with either a laser scanner or the inEos Scanner (Sirona Dental Systems), which can rapidly scan individual teeth as well as complete jaw models. The technician scans the model sent by the dentist and designs the copings and/or framework on the computerized image of the dies. Once the design is complete, the technician selects the appropriate material, (zirconia, alumina, or spinell) and mills the abutment(s). The zirconia copings and frameworks must be sintered in a sintering oven before adding porcelain. Alumina and spinell can be layered immediately. The restorations are then created, with porcelain pressed or stacked by the technician, resulting in fully customized, extremely strong, and highly esthetic restorations. The benefits to the lab are significant. The entire process of coping and framework fabrication is automated, requiring fewer laboratory personnel and materials. When considering the investment in materials, equipment, and training required along with savings and efficiencies in labor, the entire process is highly cost-effective and profitable.

The Cercon Smart Ceramic System from Dentsply Ceramco uses the high strength of zirconia in the fabrication of all-ceramic esthetic restorations. It is indicated for single-unit anterior and posterior crowns and 3- to 4-unit bridges with anatomic lengths of up to 47 mm. The Cercon system is actually a CAM system, with the laboratory technician creating a wax model using all of the familiar materials and techniques. The model is then scanned optically and milled automatically from a zirconia blank. After milling, the presintered zirconia is still soft, and adjustments to contour can be easily made. When the final shape is achieved, the zirconia framework is placed in the Cercon high-temperature sintering furnace. During this process, it shrinks to its intended size and fit. The resulting sintered frame is extremely dense and strong. The technician then layers and customizes the ceramic material. The Cercon CAM system includes the Cercon brain, the scanning and milling system, Cercon heat, the sintering furnace, and Cercon base, the Cercon blank materials. Cercon restorations exhibit excellent physical properties and excellent esthetics, along with ease of use for the dental laboratory technician.

Procera All-Ceram restorations (Nobel BioCare) were introduced in 1994. The system uses a high strength aluminum oxide core along with translucent veneering porcelain. The copings are made of densely sintered, pure aluminum oxide. Their patented process is unique. The Procera laboratory technician scans the dies with a laser scanner, and enlarged dies are fabricated. The alumina powder is dry-pressed on the dies, milled to specified thicknesses, and sintered in a sintering oven. The resulting ceramic cores are densely sintered, translucent aluminum oxide, providing the veneering material with a warm underlying dentin shade for subsequent porcelain build-up. The process is indicated for single-unit anterior and posterior crowns.

Kavo Everest is a laboratory-based CAD/CAM milling system made of four components: Everest scan, Everest engine, Everest therm, and Everest elements. Everest scan uses a charge-coupled device (CCD) camera to scan a specially reflective preparation model to achieve a 1:1 scanned and stored digital image in 4 minutes (Figure 5). The dies are placed on a rotating turntable that allows for complete and highly accurate marginal scanning. Kavo Everest engine is the heart of the system, featuring 5-axis movements of its dual-cutting tools, and allowing for a high degree of detail and precision (Figure 6). Kavo Everest therm, the Kavo sintering unit, is designed to ensure uniform internal heat distribution for accurate sintering of zirconia. Kavo Everest elements are the diverse basic materials used by Everest. These include pure titanium for implant abutments, translucent leucite reinforced glass ceramics for esthetic crowns and veneers, and zirconium oxide for copings and frameworks.

Precident DCS (DCS Dental) is alaboratory-based CAD/CAM system of three components: the Preciscan® laser scanning system, the Dentform software, and the Precimill® milling system, which is also available on an external basis asan outsourcing option. The system is designed for flexibility; data from the scanner can be transferred by modem to an external operator of the milling unit. The Preciscan laser scanner measures 300,000 points per minute optically. Up to 14 preparations can be scanned simultaneously, including crown and bridge copings and abutments. The DC-Zirkon Ceramic (DCS Dental) is a pure zirconium oxide for crown and bridge framework. CD-Titan (DCS Dental) is a high-strength millable titanium block for crown and bridge abutments. DC-Tell (DCS Dental) is a reinforced polyamide fiber with numerous low-cost restorative applications.

Lava 3M/ESPE is a laboratory-based all-ceramic CAD/CAM system that was introduced in 2003. The system millszirconium-oxide in the fabrication of metal-free crown and bridge abutments for numerous anterior and posterior prosthetic requirements. A custom veneering ceramic is a component of the system. The three components of the Lava system are scanning, computer-aided framework design, and milling of presintered zirconia blanks. The zirconia frameworks are available in 8 different shades, allowing for excellent esthetic results. After milling, the frameworks and copings are sintered to achieve final strength and dimension.

Conclusion

The revolution occurring in dentistry as a result of recent advances in CAD/CAM technology is profound. For the first time, dentists are able to take full control of esthetic crown, veneer, and inlay/onlay restorations in their offices. Dental laboratories, both large and small, are able to fully streamline and automate their processes, saving time and money while delivering high quality, highly esthetic, and long-lasting restorations.

About the Author

Eugene L. Antenucci, DDS, FAGD
Attending Dentist
Montefiore Hospital and Medical Center

Private Practice
Huntington, New York

Certified CEREC® Basic Training Instructor


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Image Gallery

Figure 1  The CEREC<sup>®</sup> 3D design software, used chairside by dentists and auxiliaries in the design of inlay, onlay, partial crown, full crown, and veneer ceramic restorations.

Figure 1

Figure 2  IPS Procad<sup>®</sup> Blocks by Ivoclar Vivadent are used by CEREC 3D and CEREC inLab for milling inlays, onlays, partial crowns, full crowns, and veneers. The chemistry of Procad porcelain is nearly identical to Empress<sup>®</sup>2.

Figure 2

Figure 3  The e.max ZirCAD block by Ivoclar Vivadent is used with the inLab system to fabricate zirconium copings for single-unit crowns and small-span bridges.

Figure 3

Figure 4  The CEREC<sup>®</sup> inLab milling and scanning unit, manufactured by Sirona for CEREC inLab, and distributed exclusively in the United States by Patterson Dental Supply (St. Paul, MN).

Figure 4

Figure 5  Kavo Everest<sup>®</sup> CAD design software with its “check bite” utility for achieving proper occlusal morphology, form, and opposing occlusal contact points.

Figure 5

Figure 6  Kavo Everest<sup>®</sup> engine, features 5-axis movements of its dual-cutting tools and allows for a high degree of detail and precision (shown here milling pure titanium).

Figure 6