Laboratory Technology 2014: Identifying Material and Equipment Trends and Changes

In 1979 Sony Corporation introduced the Walkman, the first truly portable, personal music player. It played audio cassettes and may have had a built-in AM/FM radio receiver. However, new digital techniques for storing and playing music soon gained favor, and by 1984 Sony released the Discman, a portable CD player. In January 1998, Audible.com unveiled the first portable digital audio player called the Audio Player, boasting 4 MB of memory.

Most audiophiles insist that vinyl records produce the richest, most vibrant music. Today, however, Apple® iPod variants, MP3s on mobile phones, and digital music streamed over the Internet rule the day. It seems the digital trend has been adopted by mainstream America, even if traditional methods are considered better by some.

Navigating through technology trends and changes can be challenging, especially for an industry—like dentistry—that has been traditionally full of hands-on, manual (analog) processes. To have the best chance of succeeding, dental practitioners must be aware of current developments and identify where new materials or technology can fit into and benefit their practice and/or the dental laboratory with which they work.

Material trends for indirect restorations continue to move away from metal. According to a recent survey, in 2005 83% of restorations fabricated by responding dental laboratories were metal-based, with 17% metal-free. In 2014, only 40% of restorations were metal-based and 60% were metal free.¹ Technology isn’t just about electronics and equipment; it includes advances in materials as well.

Hybrid products that combine two commonly used materials are gaining attention for indirect restorations; desirable characteristics of each material can be blended together to improve the final product. For example, Lava™ Ultimate (3M ESPE, www.3MESPE.com) takes the machinability and convenience of a resin and improves its durability with the addition of a small amount of zirconia. In the case of Vita Suprinity® (VIDENT, www.vident.com) or CELTRA™ Duo (DENTSPLY, www.dentsply.com) the esthetics of a glass ceramic is combined with increased strength via the inclusion of additional zirconia. These newer micro- or nano-impregnated materials show promise, and while they may be available from some laboratories, they appear to be targeted for practitioners using chairside CAD/CAM systems.

For zirconia-based restorations, the trend is toward pre-shaded zirconia options. Typically, milled zirconia crowns are infiltrated with shading liquid by either dipping or painting the restorations prior to sintering. In the early days, there were a small number of liquids that provided good substructure shade options for porcelain-fused-to-zirconia restorations. As full-contour zirconia gained popularity, 16 different liquids became available to shade zirconia before sintering. Today, disks already have the shading pigment introduced at the time of manufacture by the zirconia disk/frame provider and dipping is no longer necessary. It generally provides more consistent shade results, fewer manufacturing steps, and fewer internal remakes.

Companies have developed additional pre-sintering characterization stains for zirconia. These stains are applied by painted brush strokes. It allows technicians to take advantage of the wicking property of pre-sintered zirconia to bring stain pigments below the crown’s surface, creating a more lifelike depth to the shade. Purple and blue stains are available to add to the cusp tips or incisal edges of crowns to enhance the appearance of translucency.

Another zirconia-related development, which industry should expect to see by early 2015, is a new generation of translucent zirconia. Suppliers of zirconia disks and frames now have access to a new formulation of zirconia powder that offers significantly improved translucency compared with today’s high-translucency options. While actual measurement of the improvement in translucency has not been claimed yet, the samples being shown are dramatically more translucent to the naked eye. These new super-translucent zirconias have flexural strengths of only around 600 MPa for the traditional three-point bend tests compared to the 900 MPa to 1200 MPa range of today’s high-translucency zirconia. They sacrifice flexural strength for translucency and, therefore, may not be ideal for double-pontic or cantilever bridges, but they will be a viable option for single units in the anterior and posterior regions. These new zirconias are expected to be offered in both unshaded and pre-shaded varieties.

Dental laboratories are accelerating the adoption of CAD/CAM equipment and technology. According to the same survey cited earlier, in the past 5 years the number of laboratories with in-house CAD/CAM equipment has more than doubled from 34% to 70%. Even 61% of one- to five-person laboratories responding to the survey have at least a scanner in the lab.¹

Laboratory scanners have traditionally been used for scanning working models. However, most of today’s scanners are also capable of scanning impressions. Laboratories are beginning to recognize impression scanning as a viable workflow for many posterior cases.

Major scanner manufacturers are adding features to their newer models. For example, 3Shape’s D900 (www.3shape.com) scanner has additional cameras and color capability. Medit’s Identica Blue (www.meditdental.com) scanner uses blue light instead of white for better data acquisition. Both models have texture scanning capability, which allows technicians to draw on their models and have that information detected and represented within the digital file. Dental Wings’ iSeries (www.dental-wings.com) is a dedicated hands-off impression-only scanner. It is being targeted primarily for practitioners, but could be very useful in a laboratory as well.

Digital impression systems, while not new, are featuring innovative updates to older systems, and there are new providers as well. The conduits or portals to move scan data from the practitioner’s office to his or her laboratory’s CAD workstations are getting better and more refined. Unfortunately, with every new system on the market, a laboratory must find a solution that is compatible with its doctor’s system. Sometimes it comes in a single package or software solution. Otherwise the laboratory may need to use one program to communicate with some of its doctors, another program for a different doctor, and yet a third different workflow for other doctors.

CAD software for designing restorations has improved with additional features such as virtual articulation, bite correction, and mirroring of contra-lateral teeth. Modules are now available to design models, bars, bite splints, and partial frameworks. New libraries are available, and even for sale, for just about every dental CAD software. Technicians can e-mail 3-dimensional (3-D) virtual diagnostic models to doctors and then provide “eggshell” provisional restorations based on that diagnostic model. Currently, there are at least two companies that offer nearly completely digital design and manufacturing solutions for removable prosthetics.

Increasingly, laboratories are purchasing their own mills for zirconia, provisional materials, and wax, as multi-material and heavier-duty mills have come down in price in the past decade.

As 3-D printers become more prevalent in dental laboratories and milling/production centers, there are several available technologies from which to choose, such as jetted-resin (eg, Projet® 3510 MP, 3D Systems, www.3dsystems.com; and Objet Eden260V, Stratasys, www.stratasys.com) or stereolithography (3Dent™, EnvisionTEC, www.envisiontec.com). Materials used in these printers are resins that are cured when exposed to ultraviolet (UV) light. Jetted-resin printers spray resin onto a tray from a microjet, much like an inkjet printer does with ink onto paper; a UV light then cures the resin in place. Stereolithography uses a similar resin held in a reservoir. Selected areas of a build tray or platform are illuminated by a UV light or laser, curing the resin in that particular spot. After curing is done on that layer, the build tray is slightly raised or lowered and the next layer of the model is printed. These types of 3-D printers are primarily used for printing crown and bridge models. Other products being printed in laboratories with these printers are surgical guides and orthodontic models. These printers can also print patterns for casting or pressing glass ceramics, however other models are available that are better suited or even dedicated for printing castable resin patterns.

While outside of the financial reach of most laboratories (typically > $250,000), some larger production/outsourcing laboratories have invested in 3-D printers that can print non-precious or semi-precious metals for porcelain-fused-to-metal (PFM) restorations or even surgical guides. These units use a process known as SLM (selective laser melting) or SLS (selective laser sintering), in which there is a reservoir of the metal in powder form, and a laser passes over the build tray, melting or sintering the powder together in the desired areas.

Precision design and manufacturing equipment technology will surely continue to move into dental laboratories. Forward-thinking laboratories recognize that some doctors who buy chairside CAD/CAM systems may want to outsource the design process and offer that as a service. Dental assistants are likely to start scanning impressions, and laboratories need to be ready to print models from those impressions or provide model-less restorations to their doctors. Forward-thinking doctors are likely to bring dental technicians into their office to be able to produce laboratory-quality restorations in-house. These advances in technology are eliminating many of the labor-intensive processes for a majority of indirect restorations placed today.

The American Dental Association is supporting US efforts in developing International Standards to qualify the performance of scanners, mills, and dental materials. There are even standards in development to provide a universal data structure to follow a patient’s case from start to finish, storing and passing critical case information to every person involved at every step of the manufacturing and delivery process.

Those who embrace technological changes eagerly await what’s next.

1. Molinaro K. Digital trends you need to know. Lab Management Today. May 2014.

Chris Brown, BSEE
Applications Engineer/Dental Specialist, Axsys Dental Solutions, Wixom, Michigan; former Business Manager, Apex Dental Milling, Ann Arbor, Michigan