Applying Numerical Simulation to Orthodontics with Niigata University

Q1: When did you start thinking about applying numerical simulation to medical treatment?

Dr. Nihara: I started to study simulation during my degree research. We look at bite gaps to treat orthodontic problems with teeth alignment, including inconsistency with the basal bone. My research looks at the progress of biting after surgery, and how treatment results greatly affect muscle movement around the jaw when eating.

Patient data in my thesis showed certain tendencies in the muscles used for chewing, making it important to analyze ‘biting force’ in a more in-depth way than traditional methods like electromyograms. With numerical simulation I can study biting in three dimensions in relation to the shape of the jaw and the biting force, which is important for improving corrective treatment and understanding the relationship between force, teeth, and the bone.

Q2: Did you have any difficulties in starting to use numerical simulation?

Dr. Nihara: I didn’t know much about the process as I’m not an engineer but a dentist. I began working from scratch when researching in the United States, at first with examples of old 2D linear analysis. However, advances in computers means that you can carry out analysis that had previously been difficult to do, for example from taking CT or MRI scans of the body and studying them in software.

Q3: What kind of treatments can be helped by this method?

Dr. Nihara: Teeth being corrected do not immediately move after pulling, and you must have regular visits to the hospital to check treatment. It usually takes a couple of months to see how well things are going. Numerical simulation means that we can predict the accumulation of small changes under different scenarios.

JSOL: So it takes time to see the progress, and in the first place you cannot try it with the human body?

Dr. Nihara: Yes, you typically have to rely on so-called animal experiments to understand biological reactions, ideally in monkeys that have similar-sized teeth to humans. However, it’s more common to use rat teeth, which have differences in size and structure from humans. Numerical simulation of human teeth is therefore important as an educational tool for visualizing an orthodontic treatment for patients, and for demonstrating different effects ‘on the fly’ to graduate students.

Q4: Can you tell us about a recent research case?

Dr. Nihara: The image above is an example from a postgraduate student, looking at the distribution of force applied to the jaw after surgery. You can see that a great deal of power is applied to the lower jaw. Only the lower jaw is muscled here, but it seems the upper teeth will also be affected. In the future, this would useful to show the patient.

We’ve also been working on basic research, in this case using Simpleware software. Above is an example of a rat tooth, where simulation tells us that tooth movement is slightly different than previously known. This method also benefits research into how cells in culture react to force within a certain environment, and to the under-explored area of how tissues are affected by stress.

Q5: Can you tell us about the future of your work?

Dr. Nihara: I would like to cooperate with the Faculty of Engineering in the future, but it’s important if using the same software not to move too far away from work that will benefit the clinic. However, numerical simulation can help the clinic to understand treatment, and Niigata University is keen to promote collaboration between medicine, industry, and academia. There are many things I’d like to do in my own research, but for now I’m focused on studying forces in orthodontics, post-surgical outcomes, and helping patients with poor teeth alignment.