Effect of Compression Force on Apoptosis in Human Periodontal Ligament Cells

The effect of compression force on periodontal ligament (PDL) plays a critical role in orthodontic tooth movement. However, little is known about this effect on apoptosis and the underlying reactive mechanisms in PDL cells. This study focuses on the application of compression force associated with reactive oxygen species (ROS)-induced apoptosis in PDL cells. Following the application of orthodontic force to maxillary first molars, the molars were investigated using immunohistochemical analysis. The cell cycle and apoptosis were assessed in compression force-treated PDL cells using flow cytometry. Furthermore, we assayed the effect on ROS generation by DCFDA fluorescence. In vivo study revealed an increased number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and caspase 8-positive cells in the orthodontic force group. In our in vitro study model, the compression force increased the G1 phase and apoptotic cells. A large increase in the intracellular ROS levels in human (h) PDL cells was observed in the compression force group. Taken together, these results provide new information on compression force-induced G1 arrest and apoptosis in hPDL cells.