Designing and Assembling an Imaging Device for "The Worst Possible Environment for Imaging"A Dental Imaging Device Case Study
3D virtual model of teeth. The data can be rotated for close examination, and exported to a lab for the fabrication of prosthetics.
Dental Imaging Device Assembly
Dental Imaging Device Features
• Compact, elegant design
• Sealed for hygienic sterilization
• 6-axis alignment, 5 µm precision
• Precision centering and bonding
• FDA-qualified facility and procedures
Forget the "Goop" – Create 3D Virtual Models of Teeth with Digital Imaging Technology
A new medical imaging product was being developed for making precise 3D virtual models of dental patients' teeth. Instead of oral gel casts, and all the discomfort that goes along with them, this product would enable dentists to create accurate 3D virtual models to be used for fitting prosthetics, including crowns, bridges, inlays/onlays, etc.
The design for the overall system was a combination of both imaging hardware and specialized image-processing software. Image data would be acquired with a slender hand-held "wand", not much larger than an electric toothbrush. The dental technician would insert the end of the wand in the patient's mouth, and move the tip of the sensor above and around the teeth in the area of interest, while monitoring progress of the virtual model, in real time, on a video display. The sophisticated optics and sensors in the wand would gather data to enable the system to build a precise 3D model of teeth and gum area. All this would be done in just minutes, without any discomfort.
The 3D virtual model had to be at least as precise as those obtained with physical impression gels, and the device also had to maintain precision in the event of accidental rough handling, and through frequent hygienic sterilization procedures. Once the design and prototype stages were complete, the goal was to build and deliver hundreds of these units per quarter, requiring fast volume ramp-up.
Fortunately, they Chose Zygo
The customer had the expertise for the image-processing part of the system. However, they needed an experienced resource to handle the design and volume manufacturing of the precision electro-optical imaging system in the wand. Choosing the right firm for the job was absolutely critical. Failure of a previous design/prototype firm nearly put the customer's startup company out of business before it got off the ground. Their prototypes didn't work, due to both design and assembly errors, so the customer was unable to prove their technology, which was a critical milestone in their plan. Since this imaging device was the startup's only product, their success or failure hinged on the development of the wand. The bases were loaded and they were counting on Zygo to knock it out of the park. Zygo's reputation and expertise with engineering and manufacturing precision electro-optical assemblies, and our reputation for completing projects on-time and within budget, made us the logical choice to handle the challenge. And that's exactly what we did.
Precision Electro-Optics in "The Worst Possible Environment for Imaging"
Zygo was involved in the project from the ground up, and would be responsible for seeing it through from concept through volume manufacturing. The degree of precision required for medical device applications is challenging enough; making it rugged enough to stand up to the rigors of everyday dental office use introduced an added level of complexity. As one of the product's innovators described it: "The inside of someone's mouth is the worst possible environment for imaging. It's dark. It's wet and it's shiny. The person's tongue gets in the way, teeth are translucent, and people rarely sit still ". 1
Zygo developed the optical design and tolerance specifications for the imaging wand, including integration with the customer-specified imaging cameras. The wand features metal-encased optics, a beam expander section with user controls, and focusing elements leading to three digital imaging devices, and a narrow-band illuminator. The metal housing was designed to keep all components in precise alignment, even in the event of being accidentally dropped. Materials were selected based on medical compatibility, manufacturability, as well as aesthetic and ergonomic design. All optical and imaging components were custom made by external vendors according to Zygo specifications.
Watch the video to see how we did it
The assembly procedure involved a customer-developed integration, alignment, and test station, based on their proprietary algorithms. Assembly challenges included high-precision alignment and registration of multiple cameras, the handling and precision alignment of very small optical components, and the use of FDA-registered processes. The specialized optics required cleanroom handling and precision centering techniques, with repeatable positioning and bonding procedures.
To ensure long-term compatibility with dental sterilization procedures, Zygo engineers carefully designed the housing, developed sealing techniques, and performed extensive leak testing procedures. Once the optics and electronics were assembled into the housing, Zygo performed the test procedures to ensure that each assembly met or exceed specification, and shipped hundreds of finished units to the customer per quarter for final integration into their overall system.
Delivery and More
Zygo's Electro-Optics group successfully accomplished the customer's goals. Production volume goals were met, and the dental wand performed – as intended – in thousands of dental practices. Production costs for the wand were substantially reduced over time through lean manufacturing efforts. The customer was depending on Zygo for a successful project, and was very pleased with the result.