Effects of Forces Used in Tooth Movement on the Periodontium of Teeth with Extrusive Luxation - Experimental Study in Rats

Abstract Objectives This study assessed 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 resorption (RR) mesio-vestibular and intermediate (RRmv, RRi, respectively) of teeth submitted (L) or not (nL) to extrusive luxation (EL). Data on hyaline areas were also assessed. Materials and Methods Forty-eight Wistar rats were randomly divided into 8 groups (n = 6) according to the combination of independent variables (the type of force and luxation): the moved [nL-C, nL-Ci, nL-I, L-C, L-Ci, L-I] and the non-moving [L-nM and nL-nM (control)]. The EL of the first right upper molar was performed under a force of 1500 cN for 10 seconds. After 15 days, TM was initiated with a force of 50 cN, with the three types of force (C, Ci, I). On the 14th day, the amount of TM was measured, and the animals were euthanized, the parts processed, included, cut at the cervical level of the molars, and submitted to staining with hematoxylin and eosin (HE). Results The results showed more significant movement for the C and Ci forces when compared to I in the groups submitted to luxation (p < 0.05). The luxation factor did not influence tooth movement, except for the Ci force (nL-Ci = 0.25 x L-Ci = 0.44) (p < 0.05). The amount of RR was not influenced by the type of force nor by the EL. Regarding the number of hyaline areas, it was not possible to visualize differences between the groups, under the conditions of this study. Conclusions The amount of tooth movement in teeth submitted to extrusive luxation was influenced by the type of force. In turn, the amount of root resorption was not influenced by the type of force or by the extrusive luxation. And in these induced experimental conditions were not sufficient to generate alterations in the hyaline areas. Clinical Relevance : The history of dental trauma and the type of force used during orthodontic treatment can influence the amount of tooth movement.