BACKGROUND: This study was performed to investigate the effect of local injection of asperosaponin VI (ASA VI) on the orthodontic tooth movement in rats.

MATERIAL AND METHODS: A total of 64 healthy female Sprague-Dawley rats were selected and divided into 2 groups randomly: the ASA VI group and the control group. For the ASA VI group, 10 mg/kg ASA VI solution was injected into buccal submucoperiosteal of bilaterally first maxillary molars, and the same volume of normal saline was given to the control group. The orthodontic force was applied to the maxillary first molars. All rats were sacrificed on days 3, 7, or 14. Tooth movement effects on the periodontium were analyzed through hematoxylin and eosin (H&E) staining, tartrate-resistant acid phosphatase (TRAP) staining and immunohistochemistry analysis. Tooth movement measurements and alveolar bone volumetric changes were analyzed using a micro-computed tomography (CT) scan. Molecular changes were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot.

RESULTS: The ASA VI group presented with a significant increase of tooth movement, osteoclast number, and the expression of osteoclast differentiation factor (ODF) compared with the control group. ASA VI also induced a significant decrease in bone volume and density and an increase in trabecular spacing and RANKL (receptor activator of nuclear factor kappa-B ligand) expression at the compression side. Furthermore, ASA VI stimulated bone formation on the tension side by enhancing OCN (osteocalcin) expression and RUNX2 (runt-related transcription factor 2) expression, increasing bone volume and density and decreasing in trabecular spacing.

CONCLUSIONS: Injection of ASA VI may accelerate tooth movement via increasing the activity of osteoclasts, stimulating bone resorption at the compression side. Furthermore, ASA VI has a positive effect on bone formation at the tension side.

Keywords: Bone Remodeling, Tooth Movement, Alveolar Process, Bone Resorption, Molar, Osteoclasts, Osteogenesis, Root Resorption, Saponins