In just the past few years, Renishaw has shown stunning versatility in 3D printing endeavors—mainly assisting other organizations. With offices around the world, Renishaw experts best known for their knowledge in metrology and measurement have worked with others engaged in developing complex parts from America’s Cup sailboat parts to orbital implants for surgery in Nepal and mandibular implants in the UK—just to name a few items. The medical field has always been a center of focus for Renishaw however, evidenced with the opening of the Renishaw Healthcare Centre for Excellence a couple years ago.
Now, Renishaw is turning their sights toward the dental arena, working with Cardiff University Dental Hospital to research 3D printing of CoCr removable partial dentures. While all involved in the research realize the importance of and the growing popularity of implants, they also see that removable partial dentures (RPDs) are still in high demand. Currently, they are produced in wax and then cast manually, or designed digitally and then either cast in-house or through another party.
In line with some of the major benefits 3D printing can offer, Cardiff University Dental Hospital has sought to improve quality and efficiency in production as well as decreasing costs associated with miscasts.
“There are numerous variables that can result in a miscast as a result of the protracted workflow and complex nature of an RPD,” states the Renishaw team in their recent case study. “In addition to miscasts a number of other factors can affect the need for a remake including design changes, longevity between appointments and/or impression inaccuracies which may be attributed to the inexperience of dental undergraduates in the teaching environment. Industry feedback suggests there could be between 14 to 20% of castings requiring remakes, figures which would be unthinkable in most other manufacturing industries.
“With increasing environmental and economic pressures it’s critical that this situation is brought under control so that lab efficiency can be further enhanced and quality dental care be made available to a larger proportion of the populace.”
David Cruickshank is a member of the Renishaw team, as well as a PhD student focusing on digital denture design. He also has a penchant for 3D printing, especially in metal, and this project led to his thesis with research on furthering digital design, examining materials and how they affect performance, and how to use additive manufacturing effectively for RPDs.
In creating the new manufacturing technique for RPDs, he also worked with the following professionals from CUDH:
- Roger Maggs RDT, Senior Chief Dental Laboratory Manager
- Liam Addy, Consultant in Restorative Dentistry
- Paul Clark RDT, Senior Dental Technologist
The team found that in using AM processes, they could take advantage of nearly all the benefits found in the progressive technology, including an improved bottom line, less waste of materials overall, better health and safety features, and less environmental impact. With 3D design they could also easily make refinements to RPDs and re-print at will, enjoying a more expedient workflow too.
“Once the master model was scanned it was imported directly into the Freeform software,” explained the Renishaw team in their case study. “From here the operator can start to identify the insertion axis and block out undercuts. The undercuts can be varied to allow for tighter or looser retention. Also at this time, clearance from the gingiva can be dialled in to accommodate acrylic thickness.
“Using the Haptic arm can be a little alien at first but soon becomes second nature and the user will be quickly designing occlusal rests with intricate reciprocal and retentive arms.”
Using wax and then casting was replaced with production by Renishaw’s AM250 additive manufacturing (AM) machines after CUDH forwarded the .stl data.
“The major benefit for CUDH is that they simply send the .stl data to Renishaw for manufacture and can work on the next job instead of having to work through the highly skilled investment casting process. This can help make the lab process more efficient and cost effective,” states the case study.
Ten cases were evaluated, with each one using both a conventional and digital RPD structure. Dr. Liam Addy assessed the cases and found that for each one, the digital versions were best.
Find out more about the research for 3D printed RPDs here.
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