ABSTRACT Background: The objective of this work, of an experimental clinical nature, was to observe in vitro, through the utilization of different types of microscopes and of the study microanalytical, possible structural and chemical changes of root cement, produced by the effect of orthodontic forces generated when using braces active and passive self-ligating, after the period of alignment, leveling and expression initial torque of orthodontic treatment. Materials and methods: the study was carried out on a sample of 20 first premolars upper, 10 right and 10 left, extracted for orthodontic reasons, after informed consent, from 10 young patients 13 to 18 years of age (3 men and 7 women), which presented complete permanent dentition, with a discrepancy osseo-dental less than 5 millimeters, and with dental extraction orthodontic ally indicated for make up for the discrepancy skeletal or dental sagittal of class II existing. Everyone patients received orthodontic treatment with active self -ligating braces and Passives in shape simultaneous. The braces self-ligating assets were cemented in the hemiarcades right, While than the braces self-ligating Passives, in the hemiarcades left. The variables analyzed microscopically in the first premolars superior rights and left were: Area, volume and depth, to level of the zones of reabsorption of the tissue cement, how So too, the changes in the composition chemistry (content mineral to through of microscopy electronics analytics) in the zones of reabsorption and periphery of them. Results: Although structural and chemical changes were observed in the root cement, There were no significant differences when using active or passive self-ligating brackets. Neither there were marked differences between the samples from different patients. The size of the craters in the root resorption zone, in area, volume and depth was very similar for both types of braces. On the other hand, when studying chemical changes, through microanalysis of the tissue, I know they identified variations relative similar in both of them groups of samples first premolars superior rights and left, submitted to braces self-ligating assets and liabilities respectively. Conclusions: There are no significant differences in the biological response (structural and micro-analytical) of the dental cement, among the different samples analyzed from of different patients, when using active or passive self-ligating brackets.