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Digital Becomes Mainstream in Dentistry

By University of Michigan School of Dentistry

The 18-year-old girl came to our clinical practice with a severe challenge: a deformed maxilla, the upper jawbone that also forms part of the nose and eye socket. The deformity traced to her infant years, when at age 14 months she was treated for rhabdomyosarcoma, a rare but highly aggressive malignant tumor. Surgery and chemoradiation therapy did the trick, curing the cancer and sparing her life. But now, entering adulthood, her craniofacial bone and teeth had developed abnormally over the years, creating an expansion of her upper jawbone. It needed remedying for her to lead a full life.

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An 18-year-old patient with abnormal development of craniofacial bone and teeth. Conventional impression was impossible and required 3D scanning and planed in software.

Temporary Treatment for Long Term Health

Her treatment plan needed a multi-disciplinary team. At early ages she was seen by an orthodontist, who had optimized her mandibular occlusal plane, or the lower jaw’s contact positioning with the upper teeth. This procedure was successful in adjusting the molars’ position but failed to move the front, or anterior, teeth due to excessive movement of the teeth out of the line of contact with the opposing teeth, what dentists call overeruption. She needed extensive Oral and Maxillofacial (OMF) surgery to move her anterior mandible in pieces, or segmentally, to lower the plane of contact between the teeth, or occlusal plane. Then, the orthodontist could fine-tune her mandibular occlusal plane, bring her teeth back into alignment and give her both a normal bite and appearance. To continue her treatment and help her, we needed to extract teeth and place implants with a temporary complete denture. The temporary denture allows her to have teeth in a better position while she waits for the implants to heal and the prosthodontist can fabricate her final fixed prosthesis.

Scanning and Additive Manufacturing Solutions

There were problems preventing a straightforward denture fabrication. Her mouth had a bracket and oral device to move her maxilla. Furthermore, only very limited time was available for the fabrication of the prosthesis. She also had limited space external to her teeth and gums and internal to lips and cheeks, or the buccal vestibule. These restrictions made it impossible to take a conventional impression to create the replacement denture.

In another time in dental history, say 10 years ago, our options would have been limited. Enter 21st century digital tools for dentistry, especially both 3D non-contact scanning and 3D printing, which have quickly evolved. Even though intraoral scanning has been available in dentistry for more than 20 years, only in the last five to 10 years have scanners evolved to allow us to scan the whole mouth the way we needed to for her case.

Like many other patients, only a non-contact 3D scan of her mouth could give us the data we needed. Today, we have many choices of such scanners. These include intraoral scanners, typically using lasers or advanced structured light systems to create a complete, registered virtual impression of the mouth. We can also use 3D cone beam computed tomography (CBCT), X-ray equipment that goes beyond regular dental or facial X-rays to capture a complete 3D picture of the patient, inside and out.

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Details in 3Shape Dental System of temporary dentures design.

However, 3D data alone is not enough. With dental CAD/CAM software, again readily available from many sources, collected point clouds are converted into surfaces, usually made of many triangle patches. This creates a virtual impression, which can now be manufactured into patient-specific tools with 3D printers and milling machines.

As in software, there are now many 3D printers specific to dentistry, able to easily take the data converted from scanning. In our practice at the University of Michigan School of Dentistry, we take advantage of several software that are available and sometimes have to combine different ones to be able to achieve an ideal treatment plan, especially for complex situations like this one.

Digital tools, including 3D printing and additive manufacturing, are now widely established tools in many aspects of dentistry. The list includes:

  • Restorative dentistry and Endodontics
  • Oral and Maxillofacial reconstruction
  • Dental Implantology and Periodontics
  • Pediatric Dentistry and Orthodontics

In the case of our young patient, using these tools we planned to extract her teeth and part of the over-erupted maxillary alveolar bone. Her upper teeth would be replaced by an immediate, temporary complete denture. This denture was 3D printed after being designed and ‘planed’ in software to ensure compatibility with the existing teeth and structure in the patient. The denture was ready 90 minutes after scanning.

One week after the operation, the patient had a wonderful, normal smile with her new denture showing prominently, and normally.

Gustavo Mendonca, DDS, MS, PhD, is a Clinical Associate Professor in the Department of Biologic and Materials Sciences & Prosthodontics, University of Michigan School of Dentistry. Fei Liu, DDS, MS, PhD, is an Associate Professor in the Department of Biologic and Materials Sciences & Prosthodontics, University of Michigan School of Dentistry.
Sean Edwards, MD, DDS, is James Hayward Endowed Clinical Associate Professor in the Department of Oral and Maxillofacial Surgery and Hospital Dentistry, University of Michigan School of Dentistry.
Colin A. Mayers, DDS, MS, PC, is a private practice orthodontist in Hillsdale, Mich.

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