Inside Dental Technology
Jul/Aug 2012, Volume 3, Issue 7
Published by AEGIS Communications
CAD Scanners and Design Software
Understand product choices before making a purchasing decision.
The dental laboratory industry is changing faster than ever before. At the heart of this change is the CAD/CAM movement. This movement has been driven by the adoption of materials that require sophisticated machinery to produce the end product as well as by economic factors that force laboratories to find more cost-effective ways to fabricate crowns and bridges. Since the advent of the NobelProcera™ scanner by Nobel Biocare in 1991, scanning technology and computer-aided design (CAD) in the dental laboratory have evolved at an accelerated rate. Today, there are dozens of scanners, design packages, business models, and workflows available on the market. Even for those experienced with CAD technology, sorting through the tradeoffs among these options can be quite overwhelming. For most laboratories, a CAD system is by far the single biggest purchase they make, so ensuring that they make the right decision is critical. On a more technical level, there are four components to any CAD system to that should be evaluated—the scanner, design software, inputs (concerning which components such as intraoral scanners can be imported into the design software), and the outputs (concerning where the design files can be sent for fabrication).
The two most common technologies used in dental scanners today are laser scanners and white light scanners. Laser scanners work by projecting a laser line onto the dental model and scanning that line across the model. Cameras in the scanner capture the position of the laser line at various points on the model, and the scanning software calculates the 3D position of those points. 3Shape (www.3shape.com) and Dental Wings (www.dentalwings.com) both have multiple models of laser scanners.
White light scanners, which are rapidly growing on the market, use a projector similar to the type used to project a presentation from a computer onto a screen. This projector emits a series of stripes onto the model while cameras read how the stripes are deformed over the object. This information is used by the scanning software to calculate the 3D position of the points. Lava™ Scan ST (3M ESPE, www.3mespe.com), Ceramill Map (Amann Girrbach, www.amanngirrbach.com), and the Identica (Medit, www.medit-group.com) are all examples of white light scanners used in the US dental market today.
There are many debates about which technology is better, but, in reality, both can achieve accuracy levels under 20 microns when high quality components are coupled with software that leverages those components to their potential. For example, the scanner components experience thermal expansion when the ambient temperature in the laboratory increases. The calibration procedure and the scanning software must take such factors into account to ensure an accurate result. In the absence of this, even a theoretically superior technology can have errors well beyond clinical acceptability.
Impression scanning is available for a growing number of scanners today as well. Some technical challenges with impression scanning have limited its adoption. The first issue is that the tools used for manipulating the model after scanning are quite limited today. In the model scanning workflow, the technician can easily correct common minor impression issues. For example, if a small region of the margin is obscured by a discrete irregularity due to blood or tissue, the die can often be easily corrected by flicking off the stone in that area to reveal the margin. Although it would be ideal to have perfect impressions every time and to never have to do this, most laboratories must make such corrections on a significant percentage of cases. These types of corrections are not so straightforward in the digital world today, so it limits the number of cases that can be done this way.
Most scanners today are not suitable for dealing with scanning cases on large or semi-adjustable articulators. Due to the size of the chassis and the jigs for holding models, most scanners require removing the models from the plaster bases for these articulators. This can present serious challenges in maintaining an accurate bite throughout the production process.
Only three types of scanners are suitable for managing this issue. First among them are the handheld scanners. Some intraoral scanner companies are making their scanner available for laboratories. These handheld scanners are not limited by a chassis size, so the user has the freedom to work with models mounted on full articulators. The second scanner type that can handle articulated cases is a large chassis scanner such as the Ceramill MAP 300 (Amann Girrbach). This scanner has a large chassis with Artex mounts, which enable the user to place fully articulated models directly in the scanner. The large chassis and special model holding mounts eliminate the need to unmount and remount models. The third type is an open-air scanner called SinergiaSCAN by Italian manufacturer NobilMetal (www.nobilmetal.com). This scanner has a rotating platform on an open table with a scanning mechanism mounted to view that platform (Figure 1). The open-air design eliminates the need to fit models inside a chassis. According to the company, the open-air design is intended to enable the scanner to operate regardless of the level of ambient light in the environment, but it does recommend keeping the scanner away from windows to prevent bright sunlight from hitting the scanning area.
When evaluating design software on a technical level, it is important to consider two key factors—the initial proposal and the ease of use for achieving the final design.
The initial proposal is driven by anatomical libraries the software uses as a starting point for the design of the crown. Most design systems available today allow the user to select from one of several libraries per case. From there, the software attempts to place the anatomical form into the proper
location. However, this is not necessarily as easily accomplished by a computer as it is the human brain. 3Shape has implemented a feature called “2-contact” placement, which requires the user to indicate where on the model the crown should contact the neighboring teeth (Figure 2). Once the contacts are selected, 3Shape identifies the height of contour, cusps, and marginal ridge by placing color-coded markers on these points. If the software mis-identifies any of these landmarks, the user may help the software by moving the marker into the correct spot. 3Shape then uses this information to scale, rotate, and morph the crown into place to align the buccal and lingual contours, cusps, and marginal ridge in a manner that is similar to what a dental technician would do by hand.
Once the initial proposal is made, the user may use a series of design tools intended to adjust the initial proposal until the final design is achieved. Most of the systems have tools that simulate the technician’s wax knife to carve or add wax, and they take it a step further by allowing the designer to stretch, twist, and morph the crown.
While CAD software companies are striving for the one-click crown, this goal has proven to be elusive so far. Those seeking to purchase a system should evaluate the quality of the initial proposal and the amount of work required to achieve the final design. An important feature offered by Exocad, 3Shape, and Dental Wings, is the ability for customers to add in their own library or third-party libraries if they don’t find the stock libraries acceptable.
In addition to the basic crown-and-bridge design features, the CAD developers are continuously adding new features such as virtual articulation, which allows operators to virtually run their design through excursion to see where the design will meet the opposing dentition. Exocad has added an optional module allowing users to design night guards, which is a unique offering among the CAD players.
CAD equipment is a dental laboratory purchase that becomes more useful and more capable after it is purchased because of the updates and enhancements the companies provide. However, there is a cost; there are annual license fees, optional maintenance fees, and add-on modules.
For the most part, CAD software tends to be bundled with a scanner. For example, Dental Wings and 3Shape sell scanners integrated with their software. Exocad has taken a different approach; it offers customizable software to system integrators who want to brand the software and potentially bundle it with a number of open scanners on the market. B&D Dental Technologies,, Amann Girrbach, and dozens of other companies have partnered with Exocad using this business model. The benefit of this approach is that Exocad can focus on the software development while leveraging the multitude of scanners entering the market.
Scanner System Inputs
With intraoral scanners coming onto the scene slowly but surely, buyers want to ensure that their CAD system will be able to accept scans from their dentists. The CAD companies are modifying their agreements with the intraoral scanning companies to accept files. Currently, 3Shape and Dental Wings accept iTero™ and Lava™ C.O.S. cases. Exocad accepts iTero, MHT, and open STL file formats. The Trios® is expected to export an open format file that should be importable into any of the CAD systems that can import STL files.
Scanner System Outputs
There are two primary business models for CAD systems on the market today—closed and open systems. The closed systems require the designs to be created using the manufacturer’s materials or fabrication facility. These systems tend to be well integrated and provide consistent, predictable results as well having a lower price for the capital equipment; however, their per-unit costs are typically higher than the open systems. Open systems can send design files to any open milling center for fabricating parts. The hardware costs for these systems tend to be high, but the per-unit costs are lower than most closed systems. When an open system is sending a file to a new open mill for the first time, typically the milling center needs to go through a “dialing in” process to identify the appropriate parameters to achieve optimal results.
Making Your Buying Decision
So how can laboratory owners sort through all the options to find the right one for their particular needs? There are countless technical tradeoffs between all of the systems on the market today, but on the business level, there are three factors to consider.
The first consideration is whether the system consistently produces the intended products for the laboratory. The best way to evaluate this is to outsource to milling centers that use the equipment being considered. Trying out the system and evaluating the end product enables the potential buyer to assess the materials, design quality, and fit.
The second consideration is the level of technical support the vendor provides. All CAD systems have obstacles and pitfalls to overcome. Some have fewer than others. It is critical to work with a vendor who will be readily available and knowledgeable to provide the guidance to overcome those issues quickly. This is particularly important to ensure that production flows smoothly in the laboratory.
The third consideration is understanding the total cost of making the restoration to ensure a healthy profit margin. This includes the initial purchase, add-on modules, annual license fees, fabrication costs, and scan and design labor.
With a growing community of laboratories using these systems, there is more knowledge than ever before about which systems are working best in various laboratory environments. Tapping into this knowledge is easier than ever before with online resources such as training videos and online forums. Dental Lab Network (dentallabnetwork.com), for example, has an active community of members with a wealth of CAD/CAM experience. These members are discussing the latest trends every day. As the adoption of these systems is accelerating, most laboratories are within a short drive of a neighbor laboratory or milling center that would welcome the opportunity to allow them to see a system operating in a real production environment. By taking advantage of opportunities and learning from others, buyers can sort through the options more swiftly and identify the systems that meet the specific needs of their laboratory.
CAP is a milling center and a distributor of the 3Shape CAD system and the Roland mill.
About the Author
Rob Nazzal is the chief executive officer of Custom Automated Prosthetics (CAP).