To assess hypoxia-inducible factor 1α (HIF-1α) expression levels in the periodontal tissues of the pressure side during orthodontic tooth movement in rats.

A total of 50 male 6-week-old Sprague Dawley (SD) rats were randomly divided into 10 groups of 5 rats each. The upper left first molar was the experimental tooth and was pulled mesially with an orthodontic force of 10-15 g for 0, 1, 3, 6, or 12 h, or 1, 3, 7, 14, or 21 d. Routine five-micrometer paraffin-embedded tissue sections were processed for HE staining and immunohistochemical staining for HIF-1α. The Image-Pro Plus system was used to quantitatively analyze the stained slices.

The expression of HIF-1α in the periodontal tissue of the pressure side changed during the process of orthodontic tooth movement. The expression of HIF-1α increased immediately after loading for 1 h, reached a small peak at 3 h, and then decreased. After 12 h, the expression increased again, reached a peak after 1 d, and then gradually decreased to near the pre-loading level (P < 0.05).

There were differences in expression of HIF-1α in different groups in the periodontal tissues of the pressure side during orthodontic tooth movement in rats.