DENTAL


The Zero Gravity 3D system can be used for defect detection


near infrared light to see these lesions. He’s developed a prototype, pre-clinical, laboratory- based imaging instrument, and is applying to Barts Charity for a grant for further work. When a tooth de-mineralises, some of the


enamel crystal structure is broken down and dissolved in the acidic saliva. Enamel crystals are transparent to infrared light, but demineralised areas will scatter infrared. ‘Tis allows us to image


Software digitises and performs the 3D function


Dental implants can be checked with the Zero Gravity 3D system


My work is


inside the tooth where these lesions have formed and how deep they have gone,’ explained Tomlins. ‘My work is really trying to create 3D images to measure the depth, or severity, of these lesions in between the teeth, and then provide that as a measure to dentists, rather than using x-rays. And it’s safe. One thing we want to do before going to patients is finalise the protocol for how to measure these things [lesions] in the mouth.’ Aſter this protocol is complete, the technology can proceed to a clinical trial. One of the challenges of bringing this type


of imaging technology to the clinic is trying to drive down the cost for what are fairly expensive pieces of equipment, in comparison with those used for a bitewing dental x-ray. Tomlins will use some of the Barts Charity grant to source lower-cost components, in order to turn a bulky and expensive lab setup into a much smaller bitewing x-ray replacement. He hopes to start moving to clinical work in the next year.


Freeze frame Moving from diagnosis to manufacturing, the IT Technological Institute (ITI) in Spain has developed the Zero Gravity 3D system, a scanner with a 16-camera configuration to ‘freeze’ parts under inspection. One of the uses for which the system was designed is to measure and inspect dental prostheses. What makes the system different, according


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trying to create 3D images to measure the depth or severity of these lesions in between the teeth


to Professor Juan Carlos Perez, director of the machine learning and artificial intelligence laboratory at ITI, is its use of freefall technology. Te objects to be inspected enter the device automatically, by freefall from the top or by being pushed up from the bottom, which allows the object to be captured in its entirety (360°) without the need to manipulate it and without any occlusions. Te 16 cameras are


distributed in a spatial arrangement that has been optimised to ensure accuracy. Te system is devised to inspect the kinds of components and parts that would typically go on a conveyor and have a robot reach out to grab them. All 16


cameras take an image of the object, which is then reconstructed in 3D in ITI’s soſtware. Te surface of the object can then be compared to a reference model for quality assurance.


Towards automation Focusing specifically on dental prostheses, Sergio Navarro, business development manager at ITI, added: ‘In this case, in particular with dental prosthesis inspection, we work with companies that – based on high level of quality – are currently doing it manually, with several people working in the quality control department. Tey need, every day, to check each part of their production – both their general quality, but they also need to look for various small defects that can be on the outer and also in the inner layers of each part [dental prosthesis].’ Perez added: ‘Dental layers are fairly


transparent; you’ve got to give the impression of a real tooth that has special optical properties to disperse the light and so on, so a defect inside can be miss-able.’ Te system can check for colour, scratches and bubbles on the inner layer of prostheses. Breaks and dust can get in the tooth face, in the inner layers,


but cannot be removed by cleaning the part, according to Navarro. Manufacturers want to identify defects in the range of 50-100µm, Navarro added; the Zero Gravity 3D system can identify defects as small as 20-50µm. Te system has been in development


since 2010. Te original need from industry stemmed from the automotive sector, where there was an expectation for manufacturers to develop new systems to control in-line parts such as springs, screws, nodes and other small components. ‘Te problem,’ said Navarro, ‘is that these kinds of parts are very cheap, but they need to be able to control 100 per cent of their production – manufacturers request 100 per cent quality control for each part.’ Perez agreed: ‘Tey have a high impact


on the production and the quality, and if a very simple part breaks or works badly, it can impact on safety.’ Initial feedback indicates that industry


likes the system. Navarro said: ‘We have two prototypes in our laboratory, but we are making the first steps in real companies. Tis year, we started a test in a company near us, from the automotive sector, and at the end of the year we are also looking to start a new test phase with industrial machines with another customer.’ ITI is also working on a speciality dental prosthesis project.


Perfect partner Tere has been a lot of interest and the institute is at a stage where it is looking for partners. Navarro said: ‘We have developed the technology and we need to demonstrate in a realistic scenario.’ Te team believes the system’s main


advantage, aside from the technology, is that it can work with many different parts at the same time, one aſter the other, without telling the system what’s coming next. ‘It’s very different from what’s now in the industry,’ Perez said. ‘Most of the systems are made for particular parts, so if you make 10 million identical parts a year, you need another solution.’ O


August/September 2019 • Imaging and Machine Vision Europe 27


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