Artificial Intelligence +3D Printing to Make a Good Tooth
Sun Yuchun, Deputy Director and Chief Physician of Digital Research Center of Stomatology, Peking University College of Stomatology.
Recently, in the 2020 Beijing Science and Technology Award announced by the 20021Zhongguancun Forum, Peking University Stomatological Hospital, Nanjing University of Aeronautics and Astronautics and other institutions won the first prize of Beijing's technological invention for "artificial intelligence design and precision bionic manufacturing of complex prostheses".
Research hotspot of digital technology in denture restoration
The fourth national oral health epidemiological survey report (20 18) shows that the average number of missing teeth in adults over 35 years old in China is 4.7, and there are billions of missing teeth in all ages. Dentures and dentures are effective assistants for human beings to restore chewing function.
"In the 1970s and 1980s, a French professor first applied digital technology to dentistry." Sun Yuchun introduced that in the past 30 years, the application of digital technology in the field of global dental restoration has become more and more in-depth and extensive. Digital prosthodontics, represented by computer-aided design and computer-aided manufacturing technology, has gradually matured in fixed prosthodontics, implant prosthodontics and removable partial denture prosthodontics, and the efficiency and accuracy of prosthodontics diagnosis and treatment are constantly improving.
In recent years, the application of digital technology in complete denture restoration has become a research hotspot, and more than ten kinds of digital complete denture restoration systems have appeared in the world. However, Sun Yuchun revealed that due to the high technical difficulty in modeling, recording jaw position and complete denture design, the efficiency and intelligence of denture design are not high.
"The key to judge the curative effect of denture is the design and manufacturing accuracy and bionic matching degree of denture." Sun Yuchun said that in 2 1 century, people saw the value of artificial intelligence in the field of stomatology. Artificial intelligence was originally used for oral diagnosis, and now it has been widely used in three-dimensional scanning, computer-aided design, computer-aided manufacturing, bionic material design and other fields. It can improve the design efficiency and bionic degree of denture, make denture more suitable for patients, and reduce the labor cost of traditional manual design, manufacture and fine adjustment.
More than 1000 manual models were built into the database.
However, the three-dimensional design of dentures has long relied on the CAD software based on analytic geometry algorithm in Europe and America. This software focuses on the personalized design of each tooth, which is difficult to apply and inefficient.
In recent 10 years, Sun Yuchun often used foreign software to sort out the position of each denture, but found that there was no domestic denture mechanic to sort it out.
The difference comes from different technical routes. "When designing with European and American software, the spatial position, posture and three-dimensional shape of each tooth should be adjusted interactively with the mouse one by one. Each tooth needs to consider 6 degrees of freedom, and 28 teeth in the whole mouth need to be adjusted repeatedly with 168 degrees of freedom. Traditional technicians rely on years of accumulated manual tooth arrangement experience and operational skills, and it is extremely difficult to imitate with a mouse and keyboard. " Sun Yuchun said.
Just about to give up, Sun Yuchun suddenly realized. "Why not take the dentures made by China technicians as a whole, and then adjust the three-dimensional shape parameters of dentures as a whole according to the individual situation of each patient? Just like building a house, turning the previous bricks into a whole house, this house can adapt to the environment. This may break through the bottleneck of the effectiveness and efficiency of foreign software design. "
Sun Yuchun's team scanned more than 1000 denture models initially accumulated by Peking University College of Stomatology into a computer for data modeling. Using these 1000 models, the team finally put forward a weight index system based on facial midline, mouth line, lip height line, dental arch curve (width, depth and curvature) and other key variables 10. According to these indicators, patients' information can be collected, and the most suitable standard denture template for current patients can be found in the database in a few seconds.
Now, there are nearly 200,000 denture models in their database. "At present, there are about 570 denture processing factories in China, and more than 700 denture models can be designed every day." Sun Yuchun said.
Explore the most suitable 3D printing parameter set for tooth structure
Although the efficiency of designing dentures has improved, there are still many difficulties in turning design drawings into real dentures.
Early metal 3D printing equipment imported from Europe and America was scanned by a single laser beam. The process of typesetting design is too complicated and the ability of intelligent analysis and judgment is insufficient. A large number of manual adjustment and post-polishing operations are needed, which leads to low manufacturing accuracy and high material waste.
"At that time, the accuracy of the key parts of dentures printed by general foreign printers was only 100- 150 microns, but it could reach 30-50 microns with our printers." Sun Yuchun said.
Laminates make dentures more realistic.
From cusp to root, color, transparency and hardness are gradually changing. How to prepare bionic materials by artificial intelligence design and fine manufacturing technology?
Zirconia is the main material for making dentures. "Europe, America and Japan have long mastered the cutting-edge technology for the preparation of oral zirconia materials, but the zirconia materials they produced in the early days only have a single color, transparency and hardness, and the mechanics and aesthetics are' mismatched' with the hard tissues of natural teeth, which is also a research hotspot and difficulty in the field of dental ceramic materials worldwide." Sun Yuchun pointed out that in order to make dentures show different colors, transparency and mechanical properties from top to bottom, the research team laminated zirconia materials, and each layer was hidden.
"We pressed six kinds of zirconia containing different proportions of yttrium oxide together according to a certain structure, and established a bionic interface with two-way gradient infiltration on each layer to imitate the enamel layer of natural teeth, so that the denture will not be broken between layers during the manufacturing and sintering process, and the manufacturing accuracy will not be reduced." Sun Yuchun said that this technology has solved the problem that the hardness and elastic modulus of denture occlusal surface are much higher than that of natural enamel to a certain extent, and improved the bionic matching degree between oral zirconia restoration and remaining natural teeth in function and aesthetics.
Today, eight products developed by this scheme can completely replace imports and have been exported overseas. Bionic zirconia products have been promoted to more than 20 countries around the world, and nearly 10 million pairs of dentures can be produced every year.
"Twenty years ago, China's related products in the field of digital prosthodontics basically relied on imports. Now, domestic key technology products not only fill the domestic gap, but also reach the international leading level, and realize the' zero' breakthrough of China's independent high-end dental medical technology and equipment in the global dental market. " Sun Yuchun said.