Russian scientists discovered how chewing pressure affects gums and the durability of dental prosthetics.

The article was published in the "Russian Journal of Biomechanics." The research was conducted with financial support from the Perm Scientific and Educational Center for "Rational Subsoil Use."

In cases of complete or partial tooth loss, removable denture prostheses are often installed. They are considered the most cost-effective method for restoring aesthetic and chewing functions. However, these structures are subjected to significant loads during use, which can lead to the base of the prosthesis breaking. To create higher-quality prostheses for long-term and comfortable wear, it is crucial to determine the loads that an artificial dental arch can withstand and how they affect physiological processes overall.

“A removable denture prosthesis is a plate (base) resembling gums with artificial teeth. This design can completely or partially replace the masticatory apparatus. However, it is not durable. During chewing, it undergoes loads that can eventually lead to base failure. Therefore, to manufacture such prostheses effectively, load modeling is conducted to assess their strength and reliability,” says Sergey Muslov, a professor at the Russian University of Medicine, candidate of physical and mathematical sciences, and doctor of biological sciences.

“However, the stresses that form in the oral mucosa are typically not considered in modeling, even though it plays a significant role in distributing loads to the surrounding soft and bony tissues of the jaw. As a support for the prosthesis, the mucosa can experience excessive stress, leading to changes in physiological processes and the development of diseases,” explains Evgeny Chizhmakov, an assistant at the Russian University of Medicine.

Researchers investigated the stress-strain state of an immediate denture (which replaces one or several teeth) with a printed dental arch and a base made of polymer materials. They modeled gradual loading of the structure to evaluate the potential for large cracks to form and the levels of developing stresses in the soft tissues.

“The model represented a lateral section of the jaw and consisted of the dental arch, a connecting layer, the base of the prosthesis, and bone. Loads characteristic of chewing during meals – ranging from 100 N to 500 N at various angles – were applied to the structure. As the load increased, the maximum stresses also rose. The lowest stresses at a load of 500 N were observed in the gums, while the highest stress values were recorded in the connecting layer,” shared Alexey Nikishenko, general director of the "Design Bureau of Technical Rehabilitation Means" LLC and candidate of technical sciences.

The model elements have different material "sensitivities" to loads. The highest sensitivity was recorded in the connecting layer, while the mucosa showed low sensitivity. “The presence of a crack in a structural element does not necessarily indicate its immediate failure. Under certain subcritical stresses, it may not develop, allowing the defective element to be used for some time. Microcracks can initially form in polymers during production. By understanding the mechanical stresses acting on the prosthesis, it is possible to track the period of large crack formation that leads to brittle failure of the base,” explains Vladislav Nikitin, an associate professor in the "Computational Mathematics, Mechanics, and Biomechanics" department at PNIPU and candidate of physical and mathematical sciences.

Considering the properties of the polymer material, the scientists calculated that starting from a size of 1.88-2.69 μm, a microcrack would develop almost instantaneously, which could lead to a loss of continuity, functional properties, and ultimately, structural failure.

The researchers also calculated the probability of large crack formation in the elements of the prosthesis. It turned out that the highest probability is characteristic of the contact zones between the dental arch and the connecting layer (0.73 percent), which is a quite acceptable value for the successful operation of these prostheses with printed teeth and a polymer base.

This research allows scientists to track the risk of excessive loads on the elements of removable dental prostheses. This way, it is possible to specify the zones most susceptible to crack formation and the development of pathological conditions in the oral cavity. The results obtained are useful for improving the quality of dental prosthetics in the country.