Abstract:
Introduction: The palatal expansion is characterized by a rupture or orthopedic separation of the midpalatal suture, increasing the dental arch perimeter and moving apart the alveolar processes. Several devices have been successfully used for this separation, but not without a drawback: the posterior dental inclination, that promotes a dental expansion and not a real orthopedic expansion. The introduction of mini-implants, called absolute anchorage, allowed an attempt of minimizing the disadvantages of orthodontic expansion, combining the versatility and simplicity of the mini-implants to rapid maxillary expansion. Objective: The aim of this study was to compare the force (kgf) generated during the activation of the expansion screw, in a system of rapid expansion in vitro that was supported by mini-implants, accomplished according to two different angles of insertion and to different amounts of activations. Methods: The sample consisted of two (2) groups; the first group had an angulation of 0 degree between the specimen and the mini-implant; the second group had an angulation of 30 degrees, in both groups, 2mm thick mini-implants were used. Five (5) mechanical tests were performed on each group, and recorded the strengths of each test on every activation of 1 \ 4 turn of the expansor screw, using the software Tesc version 3.04, attached to a load intensity measurement machine Emic DL 2000®. The inter-group comparison was performed with the independent t test, nonparametric Mann-Whitney. Results: The results showed a statistically significant difference in relation to the forces compared in the following activations: 1\4; 5\4; 6\4; 7\4 and 8\4 between the two groups. The Variables of 2\4, 3\4 and 4\4 showed no significant statistical difference, maintaining a normal distribution of the compared forces. Conclusion: According to the methodology and results presented, it can be concluded that there was a statistically significant difference in the majority of the activation variables, when comparing the forces generated in the two tested angulations; and also with increasing of activations, an increase of statistical difference between the two groups was noted, showing a superiority to the forces supported by the system of the 0 ° group compared to 30° group.
