A research group led by Professor Keiji Moriyama, Dental Lecturer Yukiho Kobayashi, and Graduate Student Kwanrat Ploysongsang from the Graduate School of Medical and Dental Sciences, Institute of Science Tokyo announced that they have clarified the effects of a systemic and sustained hypoxic environment on orthodontic tooth movement in rats. The research found that while tooth movement is promoted in rats under hypoxic conditions, complications such as decreased alveolar bone levels occur after movement. This is expected to lead to the development of orthodontic treatment methods for patients with systemic hypoxic conditions. The findings were published online in Scientific Reports on July 1.
In orthodontic treatment, orthodontic appliances apply force to the tooth crown to achieve three-dimensional tooth movement. During orthodontic tooth movement, periodontal tissues experience bone formation by osteoblasts on the tension side of the alveolar bone surface, while osteoclasts are induced on the compression side of the alveolar bone, causing bone resorption. The compression side is also known to become a localized hypoxic environment. However, whether there were changes when patients have hypoxemia due to respiratory diseases or other conditions was unclear.
The research group conducted orthodontic tooth movement experiments using rats housed in hypoxic chambers (oxygen concentration lower than the approximately 21% oxygen concentration in the atmosphere). In the experiment, the research group implemented image analysis and histological analysis of tooth movement efficiency and bone remodeling, where osteoclasts resorb old bone and osteoblasts perform bone formation in those areas within periodontal tissues.
As a result, rats housed under hypoxic conditions showed enhanced osteoclast induction and tooth movement on the compression side of the alveolar bone surface compared with rats housed under normal oxygen conditions. However, decreased alveolar bone levels were observed after movement.
It was also found that under hypoxic conditions, the expression of angiogenic factors and bone differentiation markers in periodontal tissues, as well as periodontal ligament cell proliferation, were suppressed.
Under sustained hypoxic conditions, while orthodontic tooth movement speed is enhanced, post-movement alveolar bone formation is suppressed, potentially inhibiting healthy periodontal tissue remodeling.
Moriyama stated: "This research was conducted primarily by graduate student Kwanrat Ploysongsang as part of the Joint Degree Program jointly established by Chulalongkorn University in Thailand and the Institute of Science Tokyo, under the supervision of Lecturer Yukiho Kobayashi from the Department of Maxillofacial Orthognathics, Graduate School of Medical and Dental Sciences, Institute of Science Tokyo. This is the world's first experimental clarification of the effects of a hypoxic environment on orthodontic treatment, and it is expected to contribute to the consideration of treatment policies for patients with diseases accompanied by hypoxemia and the development of safer orthodontic treatment methods. This achievement is proof of the success of international graduate education through bilateral cooperation and is expected to contribute to enhancing the international presence of Japanese dental research."
Journal Information
Publication: Scientific Reports
Title: The effects of systemic and sustained hypoxia on orthodontic tooth movement in rats
DOI: 10.1038/s41598-025-07949-9
This article has been translated by JST with permission from The Science News Ltd. (https://sci-news.co.jp/). Unauthorized reproduction of the article and photographs is prohibited.