Understanding tooth extraction thanks to robot

Some individuals break out in a sweat, whereas for others, it is a regular nightmare: getting a tooth extracted. However, it is not just patients who can get really nervous about the treatment. Students of dentistry can suffer from this too. Robotics must help to close a gap in knowledge.

The problem for the students lies in the preparation, says oral surgeon Tom van Riet from Amsterdam UMC. That is due to the limited possibilities to learn and practice: ‘Dentistry students can extensively and thoroughly practice all of their treatments, such as dental cleaning or filling caries, on artificial material or even in 3D simulators. However, such qualitatively good practice methods do not exist for extractions. In the textbook, a short text states that you need to move the tooth backwards and forwards or rotate it. That’s about it. There are plastic jaws to practice on, but these are often not in the slightest bit comparable with the reality.’

Teeth have been extracted for centuries

The reason is that we know too little about these treatments: ‘Teeth have been extracted since Roman times. It was already described 2.000 years ago and is one of the most frequently performed surgical interventions in the world. Yet, incredibly, we still know so little about it’, explains Van Riet. ‘Scientific development in this area has almost stood still.’

Complex operation

Furthermore, teaching about this is difficult because it is a complex motor operation: ‘It’s hard to explain in words exactly what you do when you extract a tooth. We call it “extracting” teeth, but actually, it is more a matter of pushing’, explains the oral surgeon. ‘Moreover, no two teeth are the same. You need a lot of experience to feel which approach works when.’ Frequent practice helps, but that is increasingly difficult thanks to improvements in dentistry, especially in developed Western countries: ‘Due to the considerable attention for prevention, increasingly fewer teeth are extracted and so students have fewer possibilities to practice.’

The oldest generation of dentists sometimes anxiously ask when the robots will take over

The solution for this problem has come from a completely different discipline. Van Riet sought contact with Jens Kober, a researcher in cognitive robotics at TU Delft. Kober: ‘I was not working on this subject, but I thought it was an interesting challenge. Research in robotics often concerns applications in industry or agri-food. This is something entirely different. Robotics can contribute a lot to solving this problem.’

Robot the designated tool

‘Initially, we want to learn what happens during those extractions and then to use that knowledge to improve teaching.’ This concerns measuring movements of the dentist and the dental pliers, the forces exerted on the tooth and direction of those forces, explains Kober. But how do you do that? ‘The mouth is small. There is no space to attach sensors to the pliers or the dentist’s hand. To measure forces, you need to fix the jaw, and that is not possible during the treatment of the patient.’

Measuring with infrared is an option, but that comes with an inaccuracy of a few millimetres says Van Riet. ‘That is not good enough for the minuscule movements that we want to zoom in on.’ Kober: ‘When it comes to accuracy, precision and reproducibility, a robot is the designated tool for performing such measurements.’

Robot arm measures movement

Researchers are investigating the treatment with dental pliers attached to a robot arm with which 185 teeth were extracted from the jaws of bodies donated to medical science. The robot arm measures the movement of an experienced oral surgeon and the force meter measures the forces expressed. ‘With the help of algorithms, we hope to see patterns in the approach used for a certain type of tooth. Furthermore, we will examine whether that approach differs if large fillings are present, for example, and whether the health of the gums influences the method used. This research will solve two problems at once: we will improve the education and will learn to predict whether a treatment will become very difficult. The knowledge acquired can be used, for example, to advise a young dentist to refer a patient to an oral surgeon instead of performing the treatment himself’, says Kober.

The setup with the robot, used to study tooth extractionThe setup with the robot, used to study tooth extraction

In the short-term, the researchers hope to develop new educational material, for example 3D animations that make it clear what exactly happens during the treatment. In the long term, it might be possible to develop a simulator: ‘I can imagine that a student learns to copy certain movement patterns in a simulation environment and then, through haptic feedback, experiences which forces are associated with these. However, it will take several years before something like that becomes available’, says Kober.

Funding difficult

Finding funding for this research idea was not easy, recall the researchers. ‘There are few large calls for proposals in the area of dentistry or for connecting this discipline with robot technology. We noticed that with this research, we were moving in a new field; we are combining a centuries-old surgical method with the very latest technology’, says Van Riet.

A previous proposal for the idea within the Open Technology Programme was not awarded funding. In 2018, the research proposal received funding within Open Mind. ‘During a previous grant application, I was told that a good idea alone is not good enough. You first of all need data to show that your research will genuinely contribute something. You are competing with large projects that are already underway and have already proven themselves. With the funding from the Open Mind programme, we got the opportunity to let our idea to become more than just an idea and to lay a strong foundation for new research.’

Learning from the robot

Responses from the field of dentistry are generally positive, says Van Riet. ‘Even though the oldest generation of dentists sometimes anxiously ask when the robots will take over. I then explain that the aim is not to allow the robot to extract teeth independently, but to learn from the robot so that we can improve our own practice.’ And the patients? ‘They are very happy with the idea. In general, they think that students cannot practice enough before they are allowed to perform these treatments on the patient’, says Van Riet, laughing.

'Robot-Assistance in Understanding and Educating Tooth Removal Procedures' has received funding via Open Mind in 2018. The new Open Mind round will open mid-May.

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