Efeitos do hipotireoidismo associado ao trauma dental sobre a movimentação dentária induzida de molares de ratas

Abstract

Hypothyroidism is caused by a deficiency in hormone production by the thyroid gland. This pathology is related to several disorders, including metabolism and bone remodeling, which is a fundamental point in induced tooth movement and is of great interest for achieving success in clinical orthodontic treatment. In addition to bone dynamics, orthodontics is very concerned with dentoalveolar trauma, as this affects the supported element and supporting tissues, which are essential for the success of orthodontic treatment. The success of tooth movement in traumatized teeth depends on the severity of the injury, with root resorption being an undesirable consequence and possible to occur before, during and after orthodontic treatment. Therefore, it is important to have a definition of conducts to be adopted in relation to the moment of orthodontic treatment in patients who protect dental trauma, as well as knowledge about possible hormonal deficiencies. Therefore, the aim of this study was to evaluate the influence of hypothyroidism associated with dentoalveolar trauma on induced tooth movement in rat molars. Forty-eight Wistar rats were used, the animals were randomly divided into eight experimental groups (n=6 per group): Group 1 – control: animals that were not manifested to any experimental procedure; Group 2 (G2): animals that were kept under hypothyroidism (HPT); Group 3 (G3): animals that were admitted for dentoalveolar trauma (DT); Group 4 (G4): animals that underwent HPT + DT; Group 5 (G5): animals that underwent induced tooth movement (MDI); Group 6 (G6): animals that underwent DT +MDI; Group 7 (G7): animals that underwent HPT + MDI; and Group 8 (G8): animals that underwent HPT +TD+ MDI. At the end of the experimental period, the animals were weighed and euthanized. The hemimaxillas on the right side were removed and fixed in 10% formalin, decalcified, embedded in paraplast, cut at 5µm and stained with hematoxylin and eosin. The dosage of thyroid hormones, quantification of tooth movement, descriptive analyzes of histological slides and histomorphometric analysis of external root resorption were performed. The results were analyzed by statistical test for analysis of variance – (Anova One Way), with Tukey's post-test (P<0.05). Animals that consumed PTU (0.05% diluted in water) showed a reduction in T3 and T4 concentrations, with an increase in TSH concentration. The tooth movement rate was significantly higher 8 in animals from the HPT+TD+MDI group when compared to the other groups (p<0.05). The HPT+MDI group showed greater tooth movement when compared to the MDI and TD+MDI groups (p<0.05). Among the animals in the groups without tooth movement device, the HPT group had the smallest areas of root resorption when compared with the CTL, TD and HPT+TD groups (p<0.05). In the analysis of the groups with tooth movement device, the HPT+MDI group presented smaller area of root resorption when compared with the other groups with movement device (p<0.05). The animals in the HPT+TD+MDI group had the highest amounts of root resorption areas when compared to all experimental groups (p<0.001). The animals in the TD, HPT+TD, MDI, HPT+MDI and TD+MDI groups showed occasional disorganization of the LP and the HPT+TD+MDI group showed moderate disorganization. In the evaluation of hyaline areas, the groups that underwent TD and/or MDI (TD, HPT+TD, MDI, TD+MDI, HPT+MDI and HPT+TD+MDI) showed moderate presence of hyaline areas. Regarding the vascular alterations of the LP, the presence of giant cells, hyperemia and inflammatory infiltrate was verified in the MDI, TD+MDI, HPT+MDI and HPT+TD+MDI groups. We conclude that hypothyroidism associated with dental trauma causes an increase in the rate of tooth movement and external root resorption during orthodontic movement in rats