FGF2 and periodontitis: In the present study, the stressed rats showed significantly impaired periodontal healing and regeneration, along with a significant reduction in the number of bFGF-immunoreactive cells and bFGF staining intensity in the periodontal ligament compared with rats in the natural periodontitis healing group, indicating that psychological stress may delay periodontal healing through downregulation of bFGF expression, which is an essential factor in periodontal regeneration.