A METHODICAL STUDY OF SHAPE CHANGES IN HUMAN ORAL CELLS PERTURBED BY A SIMULATED ORTHODONTIC STRAIN IN-VITRO

Cells are known to alter their shape as a response to physical and che mical changes. Mechanical loads applied to teeth produce cellular pert urbations resulting in orthodontic movement. An in vitro model was dev eloped to simulate the in vivo strain of orthodontic movement. Calibra ted forces were applied to human periodontal ligament cells and buccal mucosal fibroblasts (controls). A biaxial strain-producing device was used to stretch vital cells grown on flexible polyletrafluorethylene membranes. In addition, a new cell adhesive, Cell Tak(TM), was employe d to examine the effect of an adhesive substrate on the cellular respo nse to two known loads. The shape changes of unstrained (control) and strained cells were evaluated by time-lapse telemicroscopy, and plots of time-dependent alterations in area and shape were recorded. The fus iform cells became more rounded over a given time of up to 1400 s. The responses appeared to be independent of cell type, the strain employe d, and the presence of cell adhesive. Scanning electron microscopy dem onstrated, irrespective of cell type, that the surface of stressed cel ls produced a striking number of microvilli as compared with the relat ively smooth-surfaced controls.