[Continuous and intermittent mechanical forces in orthodontics]

Orthodontics is based upon the cellular response to biomechanical forces. To better investigate about the manner in which cells respond to such forces, we have devised an experimental model to permit morphologic and metabolic characterization of human cells subject to a range of cyclic or static mechanical stimuli similar to those which may prevail in orthodontic-orthopedic therapy. The most recent data in the literature indicated that cyclic forces could have bigger effect on cells than continuous ones. To better understand the rationale of the cyclic force effect, a morphological study on human fibroblast was performed. We found that stretching or compression delivered an immediate and proportional deformation on cells. After 10-15 minutes the morphology of cells readapt to the new mechanical environment, this causing the lost of the biological activation. A new mechanical stimuli should be necessary to determine a new biological reaction.