Efeitos de forças utilizadas na movimentação dentária sobre o periodonto de dentes com luxação extrusiva – estudo experimental em ratos

Abstract

This study evaluated the effect of different types of orthodontic forces (continuous (C), continuous interrupted (Ci) and intermittent (I)) on the amount of tooth movement (TM) and root reabsorption of the buccal mesial and intermediate roots (RRbm, RRi, respectively) of submitted teeth (L) or not (nL) to the extrusive luxation (EL). Information on hyaline areas, thickness of the periodontal ligament and bone conditions were also evaluated. Forty-eight Wistar rats were randomly divided into 8 groups (n = 6), according to the combination of factors (nL-C, nL-Ci, nL-I, LC, L-Ci, LI] and unmoved (nM) [L-nM e, sL-nM )]. The EL of the first right upper molar was made under force of 1500 cN for 10 seconds. After 15 days, TM was started with a force of 50 cN, which was characterized as Ci or I, respectively, when the spring remained fixed and passive until the next activation, or when it was removed between activations. On the 14th day, the amount of TM was measured, the animals were euthanized and the processed parts were cut at the apical level of the molars and stained with hematoxylin and eosin (HE). The variables analyzed were the amount of TM, RR, hyaline areas, thickness of the periodontal ligament of the mesiobuccal and intermediate roots, as well as the bone area between these two root portions. The results showed greater movement for the forces C and Ci when compared to I, especially in the groups submitted to dislocation (p <0.05). The dislocation factor did not influence tooth movement, except for strength Ci (nL-Ci = 0.25 x L-Ci = 0.44) (p <0.05). The amount of TM in the teeth submitted to EL was influenced by the force type, which was higher for the forces C and Ci. The amount of RR was not influenced by the type of force nor by the EL. In the other points of the periodontal analyzed, it was not possible to visualize differences between the groups, under the conditions of this study.