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Digital Restorative Dentistry: Bringing Value to the Practice
Daniel J. Poticny, DDS
Now a multifaceted entity, digital restorative dentistry has fundamentally altered the dental industry for both dentists and laboratories. Over the past 30 years, the types of restorative materials available and the ways in which indirect restorations have been produced have changed dramatically. The use of metal has dropped to historic lows, with silica-based glass, polycrystalline, and resin-hybrid ceramics taking its place. Moreover, both dentists and laboratories have adopted digital technologies, which has enabled each to rapidly prototype restorations and provide consistent, controlled results while reducing labor costs for producing crowns, fixed partial dentures, implants, inlays, onlays, and veneers.1 Resin-hybrid ceramics, in particular, have emerged as the “modern dental materials,” which could not exist without CAD/CAM.2
With the properly trained clinician and adjunct dental team, the digital process may reduce risks associated with traditional analog restorative methods, which rely on dimensionally unstable and potentially incompatible materials that are subject to errors associated with their repeated manipulation. With a direct, virtual construction model, efficiency gains are definitively realized. The CAD/CAM-mediated process consists of a scan of the preparation quadrant/arch, its antagonist quadrant/arch, and a closed bite scan of the same to render an articulated virtual model. The restoration is designed virtually and directly using software tools to shape, form, and control occlusion for the desired restoration. When design is complete, the information is converted to a dataset, which is used by a milling device to grind or mill the desired restoration from a solid, monolithic, homogenous, industrially processed block that by definition describes modern dental materials. As such, the majority of the restoration is adhesively placed with exception/option for polycrystalline materials (eg, zirconia).
The origin for CAD/CAM laboratory techniques traces its heritage to the first commercial introduction of chairside millable ceramics in 1985. Although this was first described and prototyped as early as 1973 by Francois Duret,3 it was Dr. Werner Mörmann and Marco Brandestini who began work in 1980 leading to the first successful application in 1985 for the direct treatment of patients with CAD/CAM technology and silica glass-ceramic (Vita MK I and later Vita MK II, VITA Zahnfabrik, www.vita-zahnfabrik.com) uniquely within the context of a single patient visit without laboratory intervention.4,5 The initial system was limited to adhesively bonded inlays and onlays until 1996 when crown options were introduced. The acronym “CEREC,” or Chairside Economical Restoration of Esthetic Ceramics, became a brand name first used by Siemens AG (www.siemens.com) in 1987, then Sirona Dental Systems in 1997 (www.sirona.com), and currently, as of 2015, Dentsply Sirona (www.dentsplysirona.com).
Any Restoration Imaginable
With CEREC reporting over 35 million completed, high survival rate restorations having been produced and approximately 15% chairside CAD/CAM utilization by dentists in the United States for all available systems, the adoption of this technology will continue as an alternative to laboratory manufacture.6-8 CEREC set the initial standard for performance of these materials using the CAD/CAM process in terms of durability, predictability, and effectiveness in the treatment of teeth using the monoblock/monolithic principle.9-13 Numerous other manufacturers are now in the marketplace with chairside CAD/CAM systems, such as Planmeca/E4D Technologies (www.planmecacadcam.com), CS Restore (Carestream Dental, www.carestream.com), IOS FastScan (Glidewell Laboratories, www.glidewell.com), and others that combine a scanner with a choice of commercially available milling units for lab or chairside use, such as TrueDef intraoral scanner (3M Oral Care, www.3M.com), iTero (Align Technology (www.iTero.com), and 3Shape Trios (3Shape A/S, www.3shape.com). Lastly, the adoption of digital technologies is greater in laboratories today, even surpassing chairside utilization, owing to their productivity efficiencies and demand for CAD/CAM reliant materials.
Today, available chairside CAD/CAM platforms can, to one degree or another, produce virtually any dental restoration imaginable. The wide range of material offerings includes glass-ceramics, reinforced glass-ceramics, zirconia, polymer-ceramics, nanoceramics, resin-based composites, and polymethyl methacrylate (PMMA) materials. Long-term survival for CAD/CAM chairside-processed restorations, as mentioned, is well documented. Other factors, such as esthetic integration and morphology, while less of a factor in terms of performance, are desirable nonetheless and synonymous with the term “lab quality.” These parameters are conveniently achievable with willingness, proper training, case selection, and summary execution in the dental office.14 For those not interested in chairside fabrication, a dentist can choose to separate the digital imaging from chairside manufacturing, submitting a digital file to the laboratory for restoration fabrication. This digital file eliminates impression materials and in many cases can be performed by the laboratory without a physical model.