In this study we wanted to investigate how cyclical (vibratory forces), as noninvasive and relatively simple and nonexpensive psysical methods, could affect orthodontic tooth movement in rats. Two different vibrational frequences, 30 and 60Hz, at the force of 0.4Newton were applied oclusally twice a week for 10 minutes in experimantal rats where the first left maxillary molars were moved mesially for 2 weeks. Both vibrational frequencies inhibited the amount of tooth movement. That effect was probably caused by the inhibition of osteoclastic activity and alveolar bone resorption that is important and necessary event during the orthodontic tooth movement. We also found that vibratory forces caused increased number of apoptotic cells and marked disorganization of the collagen fibril structure within the periodontal ligament, probably due to the excessive force levels used in these experiments. All changes were more prominent with 30Hz vibrational frequencies. Future studies should include additional analysis that would evaluate the effect of the whole range of vibrational forces and frequencies on the alveolar bone and resorption during the ortodontic tooth movement. Those studies should also evaluate more carefully the frequency and the point of their application (vibrating the alveolar bone directly insead of the tooth crown). Based on the results from this study, vibratory forces, because of their inhibitory effect on osteoclastic activity and bone resorption and decceleration of tooth movement, could have a significant impact and clinical use in the prevention of the orthodontic relapse, unwanted orthodontic event that occurs immediately after the termination of treatment and present an enormous problem in orthodontics.