Advantages of Digital Removable Prosthodontics
The advantage of digital removable prosthetics is the ability to view collected clinical data such as terminal dentition, ridge relationship, prosthetic condition, prosthetic space, anatomical landmarks, anterior esthetics, and functional occlusion from various perspectives before treatment has begun. This clinical data is collected from an intra-oral scanner (IOS) (Image 1) or by scanning physical impressions or models.
When using an IOS, prosthetic variables such as impression materials and gypsum are eliminated, thus creating a 1:1 relationship between scan and soft tissue anatomy or denture. Eliminating prosthetic variables provides a better fitting and functional prosthesis when using a clinical digital workflow.
Image 1: An Intra-Oral Scanner collects soft tissue anatomy data of patients' edentulous maxillae and mandible.
The main differentiator between traditional and digital prosthetics is data. The traditional process for denture prosthetics destroys clinical data such as impressions, relationship records, and master casts. Digital workflows are Data Driven (Image 2).
Image 2
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Intra-Oral Scan or Natural Dentition for a Provisional Partial Denture
A leaf gauge was used to scan the Vertical Dimension of Occlusion (VDO). The lower right image below shows the bite scan at the desired VDO. The advantage of acquiring and collecting data with an IOS for removable prosthetics is the simplicity and efficiency of taking a digital impression (Image 3).
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Case Presentation
In honor of Veteran’s Day, MicroDental had the pleasure of working with Dr. Kyle Benton in providing maxillary and mandibular digital dentures to a Veteran this last month. The digital workflow that was used in this case will be described in this blog (Image 4).
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The clinical workflow starts with taking a wash impression as you would for a reline on the intaglio surfaces of the maxillary and mandibular dentures. The dentures are tissue conditioned with a functional impression material or polyvinyl siloxane. The wash impression is taken if the retention and stability of the dentures need to be improved.
The intaglio (tissue surface) and cameo (teeth and base) surfaces are scanned along with a bite scan. If the Vertical Dimension of Occlusion (VDO) needs to increase due to severely worn posterior teeth, the bite scan is taken at desired VDO. The bite scan is the collected clinical data of a relationship record.
These three scans of collected clinical data will provide enough information to design a set of digital dentures.
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The image above shows scanned maxillary and mandibular dentures. The dentures are not in occlusion since a new, increased VDO record was taken at desired VDO. The bite scan is hidden in order to conduct a data analysis of denture design and re-establishing the functional occlusion.
Sagittal views of scanned dentures show severely worn posterior teeth with a reverse curve of the Wilson pattern on maxillary and mandibular occlusal surfaces (Image 6).
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Maxillary Denture scan analysis shows the soft tissue anatomy and worn posterior teeth with the same reverse curve of the Wilson where pattern (Image 7).
The mandibular dentures show intaglio and cameo surfaces. Note the severe wear and pattern on the posterior occlusal surface. All mandibular teeth anterior and posterior will be lengthened to compensate for worn acrylic resin (Image 8).
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Image 9
In the photo above, the STL files of scanned dentures are then brought into the design to reset teeth according to new relationship records. Anterior denture teeth are used as a reference for mold selection and tooth position in computer-aided design (CAD). The plane of occlusion is verified on a virtual articulator to re-establish functional denture occlusion (Image 9).
In the photo below, the purple reference is now green with the proposed tooth arrangement in a white and pink denture base. This shows that the proposed denture teeth are in the same position as the existing denture, which is the reference. The definitive denture is built with base and teeth for the final milling of an Ivotion Denture in Computer Aided Manufacturing (CAM) (Image 10).
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The image above shows the patient's smile before and after the finished Ivotion digital dentures. The Veteran will now have a digital file for his new dentures. This digital file contains all collected clinical data plus the design file in case the patient needs another set of dentures. Archiving and retaining the data for their digital denture is a great advantage and benefit to the dentist and patient.
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About the author
Robert Kreyer, CDT is a third-generation Dental Technician who received his training from the US Army Medical Field Service School in 1971. He is a member of the American Prosthodontic Society, a Fellow of The International Congress of Oral Implantologists, and the past Chair of The American College of Prosthodontists Dental Technician Alliance. Mr. Kreyer received certification from Ivoclar Vivadent as a Biofunctional Prosthetic System (BPS) Technical Instructor as well as from Candulor in Zurich, Switzerland as their Course Instructor.
Robert owned and operated Kreyer Dental Prosthetics from the years 1975 to 2010. In 2010, Robert Kreyer was the first recipient of The American College of Prosthodontists Dental Technician Leadership Award. In 2011, he was selected by the National Board of Certification in Dental Technology as their CDT of the Year. In 2014, Robert Kreyer received the Rudd Award from the Editorial Council of The Journal of Prosthetic Dentistry. He is currently the Director of Removables Prosthetics at MicroDental Laboratories and Modern Dental USA where he focuses on research and development and digital workflows.
