11 Mar The rise and rise of 3D
3D Imaging seems to be all the rage – here’s why
There’s no doubt that 3D-Imaging is becoming more commonplace in dentistry. It’s easy to understand why – 3D-Images are by their very nature easier to understand and interpret, and in many cases, they offer greater detail and more information that can be gained from 2D-Images (such as traditional X-Ray radiographs).
But there is another reason. 3D-Images recorded from digital scanners can be used as an input to 3D-modeling software.
The 3D-modeling software used in dentistry is essentially the same as that used in mechanical design. And in some industries such as aerospace, automotive and motorsport, the designs using this software have been used to make high-performance parts – straight from the designer’s desk via the machines in the workshop.
This process is usually referred to as CAD/CAM – computer-aided design/computer-aided manufacturing. Another related area that is less useful to dentistry is CAE – computer-aided engineering. CAE tools allow you to assign properties to the components of the design, such as mass, tensile strength, etc, and then to ‘test’ those components. Less relevant, but we will come back to CAE.
An overview of 3D-scanning
When the writer first described a medical application of 3D-imaging during the late 1990s, the scanners used were never going to find their way into a dental surgery. They were the Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) devices used in hospitals. These devices are very specialist, very big and incredibly expensive even now. Back in the 1990s, even more so.
However, work that started at that time has led to two key developments in 3D-scanning for dentists; Intra-Oral Scanners and CBCT (Cone Beam Computed Tomography).
Intra-Oral Scanners, such as the 3Shape TRIOS range (costing from around £6,000) produce what engineers would recognise as a ‘Surface Model’. This is a detailed and accurate image of the outer surfaces of the teeth. A CBCT machine, such as the Carestream CS8100 3D range (costing around £25,000) creates what engineers would describe as a ‘Solid Model’. This can be displayed as the visible components, or else separated into the individual or groups of components – in this case, bones and teeth.
They can both be used in many ways, but perhaps Intra-Oral scans are best for creating appliances and orthodontics, whereas CBCT is the more effective for diagnosis and surgical planning.
CEREC and 3D-Printing.
Manufacturers have been trying to persuade dentists to use tiny milling machines for some time. These are generically known as CEREC system, and allow dentists to design and manufacture appliances such as crowns and inlays within their practice. However, they are expensive to buy, and sometimes tricky to use and maintain.
Peter Kettle, business development manager at DGSHAPE (a Roland company) says; “It’s true that there are a lot of machines gathering dust in clinics and labs throughout the industry. These older systems, though perfectly capable of their required job, were unintuitive and challenging to use. We saw early on how important it is to develop devices that are as easy to use as they are productive.”
Don Babbs of Awesome Technology agrees; “It has to be as easy to use as possible at chairside. Software is the complicated bit, but integration with other systems, such as your practice management system, is also a key element. Everything should work together seamlessly and in a streamlined workflow. This is part of the industry that needs standards.”
So milling machines and 3D-Printers don’t make economic sense for the volumes of appliances they can be used to make in most independent practices. That economic model changes in very large practices in dental laboratories where the technology has become very popular.
“In clinics, the most realistic way to make a profit with a 3D printer is to invest in something which can create many objects in bulk,” explains Peter. “Typically though, clinics can’t always guarantee a requirement for a large number of items, so numbers alone may not always be the only cost justification. However, you need to look at your specific circumstances. If, for example, you’re in a rural location with poor postal services, could you improve your service with an intra-oral scanner and a milling machine? Or if you’re a private practice, could you offer a premium ‘same day’ service through digital technologies?”
The latest device that dentists are being persuaded to buy is the 3D-Printer. 3D-printing (or additive manufacturing) has also been around for 25 or so years. However, early processes were messy and incredibly expensive to use. They also required materials that were simply not appropriate in a dental setting.
However, over the years, new materials have been developed, and a whole range is now available for dental applications, with appropriate medical use certifications. These materials are usually referred to as ‘resins’, and take the form of thermo-setting or UV-light cured plastics that can be applied in layers. The computer code that controls these layers is created from digital models that are in turn created from digital scans. These layers can now be applied with incredible accuracy approaching that of decent quality milling systems.
As Don says; “3D-Printing has seen a lot of changes in the last few years, and it’s still experiencing rapid change. The main area of development is printer resins. Overall, resins have got much better, and as well as moulds, new bio-compatible resins can be used for a range of temporary appliances. Availability of a wider range of colours has made a big difference to their usefulness. More importantly, entry costs have reduced because dental applications can now make use of more ‘general purpose’ printing devices.”
3D-printing is already widely used for applications such as implant guides and making the moulds for devices such as invisible aligners. The latest resins have been certified as suitable for direct printing of dentures, though these systems and materials still don’t provide a clear economic benefit for every practice.
Remember the bit about CAE?
3D-Printing, by its nature, produces layers. Like the grain of wood, printed materials may exhibit different qualities in different planes and directions. For example, they may give and crush in one direction but not when force is applied at 90 degrees to this direction. Or they may bend in one direction and be unyielding in another. In some materials, this directionality is greater than in others, and in some applications, directionality may be useful whereas in others it needs to be avoided.
It’s very important to consider this in your designs and in the materials you specify. You might find that your design software allows you to analyse the effects of directionality when you create the toolpath for your printer. If this is an option, make sure you do it.
It’s also worth noting that different resins ‘cure’ in different ways. Some air cure, some cure in UV (like the composite filling materials used every day) and some cure in heat. It’s something that can easily be overlooked when considering a 3D-Printing system.
Peter Kettle says; “Additive 3D printing is suited for certain applications like creating surgical guides for implants, or creating orthodontic aligner moulds. For applications like these, additive methods perform very well, however they do have their limitations. For example, it’s not uncommon for objects to deform or warp during the curing process, necessitating a reprint. Also, for these devices to be profitable on their own, dentists need to ensure that they have the workload to justify the investment.”
What of the future?
We asked Don and Peter for their opinions on where 3D-Printing and Milling for dentistry might go over the next few years.
Don believes that “… the evolution of resins has driven a lot of change. But resins are the part of the puzzle that dentists and people, in general, don’t understand, and they don’t ask about them. Resins are the key driver to what you can do with 3D-Printing.”
However, there have been some process developments that look set to change the economics of 3D-printing. “There are competitive and technical advantages to the various processes,” says Don. “Laser technologies such as SLA had the lead, but the development of DLP (Digital Light Protector) technologies are already matching accuracy and have the advantage of being able to create more than one piece at a time.”
Again, that sounds like an advantage for laboratories and large practices and still leaves small independents out in the cold. However, laser technology and processes such as SLA are fussy to use and prints can easily be spoiled by contaminants. They often also require further processing to finish them after printing. DLP processes are simpler. And because you can print multiple items at a time, costs don’t really rise but productivity does. So future developments using this technology may rebalance the economics in the future
For Don; “Curing the resin is the key. Cleaning the appliance produced and the printer that made it, and curing the appliance are the areas where 3D-Printing will improve and become more productive. Separate curing won’t be such a big issue.”
Milling isn’t dead
Peter Kettle says; “Over the last ten years, we at DGSHAPE have developed hardware for both dental clinics and labs. We continually develop both additive and subtractive systems, but because of their greater material flexibility and geometric reliability, we commercially focus almost exclusively on CNC milling technologies.
“As part of this product development, we have looked at ways to replace functions typically performed with additive processes with those performed on a milling machine. For example, we have developed separate systems that allow users to create models or denture-related products without the need for an additive 3D printer.
“As such, our DWX series of dental mills have been designed with a truly open philosophy, which not only increases the versatility of the machine, it also lets users operate the device in conjunction with systems they’re already familiar with and which are utilising their preferred material types and suppliers. Furthermore, there is a growing trend for dental clinics to employ dental technicians to manage the more specialised aspects like creating CAD files and finishing/staining milled prosthetics.”
Don thinks some of the processes currently used won’t change – because they don’t need to. For example, invisible aligners are currently made by 3D-Printing a mould and then vacuum forming the finished aligner over it from a sheet of plastic. Where he thinks there will be a big change is through the adoption of ‘sintered metal’ manufacturing.
“It’s always going to be a technology for dental labs as you need to make about 200 crowns in one go to make it worth doing,” explains Don. “This is because the ‘printer’ costs about £130,000, and the post-processing of metal is resource intense and costly. There are at least three post-process required. However, the materials are incredibly strong.”
Get Ready for Digital Dentistry with Pearl
Pearl Dental Software is built on a cloud platform and an architecture that makes it easy to integrate existing and future digital dentistry imaging technologies. For more information about integrations with imaging technologies call us on 0116 275 9995 or email email@example.com.