The Next Evolution of Removable Prosthetics
Written by Chris Kabot
For a long time dentures have been a sore spot for clinicians and laboratories alike. The main reason why dentures have been a neglected dental service is that the denture fabrication process is a messy and tedious experience with many patient visits. Enter digital dentistry, which we know has revolutionized many dental applications, but the time for dentures to be digitized is now. It is widely known that digital processes are proven to be time efficient and just as effective as traditional analog processes. Most of the studies that have been completed show that digital processes offer reduced chair time, better accuracy/fit, and the unique ability to store the data in the cloud for reproducibility as a form of insurance. Let’s explore some of the new processes and tools that are transforming how the clinician can address removable prosthetics.
Clinical Process:
The biggest benefit of going digital with removable prosthetics is the process. The traditional full denture process normally encompasses five appointments. The digital process automatically cuts the process down to four appointments and it is certainly possible to carry the process out in just two patient visits! The key to carrying out an efficient & effective denture workflow is the communication between laboratory and clinician. This communication process differs in the digital workflow as we now use and deploy different products. Try-ins in the digital world are no longer denture teeth set in wax, they are usually “monoblocks” or what we call BTI’s (Biofunctional Try-In). These Try-ins are typically printed or milled out of one colour and the clinician has the ability to communicate their adjustments by marking the BTI and communicating notes to the lab. The BTI can be washed with a low viscosity PVS to improve intaglio accuracy and fit of the final. If modifications need to be made to the try-in, the BTI can easily be sent back to the lab who will scan it in and modify the design. Most choose to move right to the final from this step but it is always an option to manufacture an additional try-in if need be. Going digital is not just done on the lab side, it is always an option for the clinician to add scanners and other tools to their armamentarium so they can save on their lab bill and communicate even faster with their lab network. While there is always a learning curve with implementing new protocols and processes, the reduced chair time and improved clinical outcomes of going digital with dentures is very compelling to most clinicians.
In regards to these digital processes let’s take a quick look at how the digital denture works in real life. The BTI as mentioned above is a great way for the patient to not only try the denture in for shade and fit, but for full function. Since the BTI is easily reproduced, many clinicians are choosing to communicate their adjustments without the need of sending the BTI back to the lab. This means that some are choosing to allow the patient to go home with the try-in, show their loved ones, chew and function as they normally would and experience their new life with their new prosthetic. Even if the patient comes back and decides they want the teeth to be a slightly different shape, the midline adjusted, or the shade to be changed those modifications take a fraction of the time when utilizing digital workflows and in many indications without the need for even a new try-in. Moreover what happens when the final is delivered and the patient wants some changes? Since the laboratory already has the majority of the data that is needed, communicating changes like shade or vertical can be incorporated into the master design file and a new product can be manufactured in hours, not weeks.
Manufacturing materials and processes: Milled Teeth and Milled Denture Base
Utilizing CAD/CAM to mill the denture teeth and the denture base is the first digital denture process that was brought to the industry. The current materials available for denture milling are also the most robust which makes milling the most common digital denture manufacturing process to date. Most millable denture materials have been proven to match or exceed the mechanical properties and performance of conventional denture materials. The milled denture teeth show great wear resistance and can be manufactured out of pre polymerized shaded pucks for the best possible aesthetics. There is flexibility to the workflow with teeth being milled either as a bridge or individually. Some even choose to mill the base and the teeth together to minimize post processing times. Since the teeth are customizable, the design process is robust and can capture the majority of patient indications. Millable denture bases are also capable of having fibers embedded in the pucks, which allows for best in class characterization. The only true negative to milling dentures is that milling is a subtractive manufacturing process which does yield waste. The waste and the expensive capital equipment costs coupled with the high end materials are usually reasons why the milled dentures are the premium product from a cost standpoint.
Printed denture base and pre-manufactured carded teeth
Printed denture bases are the hot topic in our industry today with some of the new developments that have hit the market. In fact, the 3D printed denture base from Carbon & Dentsply just received the first ever High Impact ISO listing for a 3d printed product. As 3d printing grows in popularity and more industry leading OEM’s begin to address the space, one can only assume the materials are going to get more advanced and robust. Printed denture bases already are showing to be some of the most accurate ways to manufacture a denture, with no tool path or undercut issues to worry about. Additive manufacturing (3D printing) is in its name, an additive process, which means minimal to no waste so the product will be more cost effective. The use of pre manufactured teeth is tested and proven over time and the teeth also come pre polished and characterized for easy assembly and finishing. Some downsides to printing the base is that no printable materials are able to incorporate fibers or multi-shade gradients. When designing a printable base with pre-manufactured carded teeth you also will only be able to address around 80% of patient indications. Patients that present with unfavourable bone bulk or Class 3 for instance, will not be candidates as the predetermined tooth geometries may not fit their clinical needs. Printing the base is undoubtedly the way of the future, the big question is what teeth will end up getting used in these bases?
Printed denture teeth and base
While we have covered the promise of printing the denture base above, we have yet to address 3D printing the denture teeth. Printed denture teeth, like milled teeth, are not constrained to pre-determined geometries so the design process should be able to address the large majority of patient indications. Current materials and machines that are on the market are usually printing monochromatic tooth structures. Some printers and materials do have the ability to print shade gradation but only from A1-A3.5 so the options are limited. Current tooth materials do not meet ISO standards for high impact which makes them risky to place in the mouth for more than one year. While printing the teeth does offer the most cost savings, most are waiting for improvements in material strength to deploy this as a long term modality.
To conclude
The digital denture frontier is evolving quickly with new materials, methods, and processes hitting the market constantly. This is an exciting time for denture prosthetics but at the end of the day it is always about putting the patient’s needs first. Choosing a valued partner that has evaluated and tested these new tools is essential for the clinician to be comfortable when deploying these new techniques on their patients. It is good to know there will be plenty of options moving forward with digital dentures and of course many smiles to follow.