Sustained hypoxia affects orthodontic tooth movement (OTM) by altering osteoclast and osteoblast differentiation, report a Japanese team.
Hypoxic conditions resulted in reduced alveolar bone levels after OTM and lower expression of runt-related transcription factor 2 and vascular endothelial growth factor. These findings, observed in a rat model, provide critical insights into the bone remodelling process in OTM under hypoxia.
Orthodontic tooth movement refers to the movement of a tooth due to an externally applied mechanical force. During OTM, the periodontal ligament (PDL) tissue around the tooth activates biochemical responses to recruit specific bone cells and chemical messenger molecules to aid bone remodelling. While PDL tissues are stretched on the tension side, resulting in bone deposition, orthodontic forces gradually constrict the PDL on the compression side, driving bone resorption.
Interestingly, recent reports indicate that a hypoxic environment lacking in oxygen supply is commonly observed on the compression side. Studies have demonstrated that oxygen deprivation can significantly modulate the formation of new dental bone. However, the precise mechanism by which hypoxia influences OTM and bone remodelling remains poorly understood.
To address this research gap, researchers at the Institute of Science Tokyo, have conducted a new study using a rat OTM model. Their research is published in Scientific Reports.
“Considering the relationship between hypoxia and OTM, we hypothesised that a hypoxic environment would alter the bone remodeling process,” study lead Professor Keiji Moriyama said.
“We utilised a closed-coil spring made of nickel-titanium to cause OTM and applied it between the right maxillary first molar and the maxillary incisors. To investigate OTM under hypoxic conditions, we housed the animals in a controlled-atmosphere chamber with an oxygen level of 10 per cent.”
The researchers observed that animals from the hypoxia-OTM group had a higher OTM distance. Notably, the alveolar bone levels on the buccal surface in the hypoxia-OTM group were significantly reduced, indicating that hypoxia may upregulate bone resorption via osteoclast activity during OTM.
During histological examination of dental tissue, the scientists identified osteoblast cells that help form new bone, arranged along the alveolar bone on the tension side in OTM groups. However, increased osteoclastic activity was found within the PDL on the compression side.
