Nikon Metrology jaw implant
Domantas Ozerenskis, Product Quality Manager, Ortho Baltic, operating the Nikon Metrology XT H 225 micro-CT scanner in the inspection department at Kaunas.
A Lithuanian medical company has leveraged Nikon Metrology inspection equipment to advance the production of jaw implants.
Ortho Baltic, based in Kaunas, Lithuania, is one of only three manufacturers of patient-specific temporomandibular joint endoprostheses in Europe. It is also the only one in the Baltic States. In 2012, Ortho Baltic made an investment into additive manufacturing technology, and more recently the company acquired computed tomography (CT) inspection equipment for quality control from Nikon Metrology.
The temporomandibular joint (TMJ) is one of the most used joints in the human body, allowing humans to talk and chew. When this joint is damaged, whether it be by trauma or illness, and typical treatment methods have been ineffective, replacement surgery is required. Patient-specific implants are usually reserved for more severe cases, but Ortho Baltic wants to make the administering of tailored endoprostheses the norm.
The company stresses this objective in its mission statement. Ortho Baltic wants to do away with the ‘one implant fits all’ mind-set by making patient-specific implants affordable and accessible.
Before production can begin, a series of scans have to take place in order to retrieve the patient’s geometries. From here, implants can be designed with CAD software, and 3D printed. Meanwhile, 3D printing is also used to create surgical guides, which advance the pre-surgical planning.
Nikon Metrology jaw implant
A 3D-printed, patient-specific temporomandibular joint.
“To create anatomical models, 3D reconstruction engineers use the patient’s radiological data to perform a 3D reconstruction,” explained Milda Jokymaityte, clinical engineer at Ortho Baltic. “The anatomical bone structures are segmented and virtual 3D models prepared. Including printing, quality control, packaging and sterilisation, the usual lead-time for a patient-specific jaw joint implant is approximately four weeks following the surgeon’s approval of the final design. From this point onwards, pre-surgical planning commences between patient and surgeon, ultimately leading to surgery completion.”
TMJ implants are designed by Ortho Baltic using the respective patients’ skull-mandible anatomical model, recreated from CT scans. Typically, implants are made from medical Grade-5 titanium alloy Ti6AI4V by direct laser metal sintering, while surgical guides and implant models are made from a biocompatible polymer PA 2200 (Nylon 12) by selective laser sintering. Inspection of the additively manufactured parts is carried out with a Nikon Metrology industrial, high voltage, micro-CT scanner.
The Nikon Metrology XT H 225 micro-CT scanner has allowed for advanced inspection with its 225 kV micro-focus source that reveals non-destructively any voids, cracks and other potential defects of the complex internal features of the AM components. The data retrieved from this scan is compared to the original CAD design to reveal any deviations.
“Micro-CT scanning is the only way to check non-destructively for voids and cracks inside a part,” said Domantas Ozerenskis, product quality manager at Ortho Baltic. “We considered a coordinate measuring machine, but it is inconvenient for taking non-parametric measurements and there is no possibility for inner structure investigation. The internal quality of implants is very important, as it determines the mechanical strength of the part.”
Nikon Metrology jaw implant
The deviation model of the joint, where the CT results are compared to the original CAD file.
Ortho Baltic requires at least 200 kV energy source to penetrate the dense materials it uses. An additional requirement was the system had a large enough working area to inspect components of variable sizes and weights. In this respect, Ortho Baltic found the Nikon Metrology XT H 225 was ideal. To support the XT H 225, Ortho Baltic also opted for a Varian 4030 digital panel and Inspect-X software.
The adoption of this technology has strengthened Ortho Baltic’s position as it aims to make affordable, accessible, patient-specific implants. In comparison to standard implants sourced from the US, Ortho Baltic claim its implants are of similar quality at half the price, though concede more extensive planning is required than when using more traditional methods.
“Nominal CAD to actual 3D printed implant comparison, geometry inspection and void detection are irreplaceable for our quality control,” Ozerenskis concludes. “The Nikon solution offers better knowledge of what we are manufacturing and gives superior precision and understanding of 3D printing errors and deviations.
“After 3D metal printing, post-processes such as sandblasting and polishing often remove thick surface layers up to 200 microns – even more in the case of other manual processes. What micro-CT data has also helped to do is adjust our CAD and 3D printing protocols to get the most accurate geometry for all our AM parts.”
