Efeito do ácido zoledrônico na resposta inflamatória em modelo de movimentação ortodôntica com ancoragem esquelética em ratos

Abstract

Zoledronic acid (ZA) is the most powerful bisphosphonate for clinical use, used intravenously, acting especially in events related to bone metastases. This research aims to compare the effect of this drug in the scarring aspects of the supporting bone tissue of a temporary anchorage device and in the inflammatory and morphological characteristics of bone tissue subjected to induced tooth movement (ITM) in an experimental model with skeletal anchorage. For this purpose, 48 male Wistar rats (350g) were used, divided into two experimental groups that received three consecutive administrations of ZA (0,2 mg/kg) or 0.9% sterile saline solution (control group) (days 0, 7 and 14). The animals were submitted to the installation of a closed CrNi spring, which was fixed between the upper left first molar and the mini-implant (MI) on day 42. The right side of both groups did not receive orthodontic strength, serving as an internal control. The displacement of the upper left first molar and MI were measured with a digital caliper. The animals were found after euthanasia on days 49th, 56th, 63th and 70th, with the upper first molar on both sides being evaluated with histological slides stained with hematoxylin and eosin in which refers to pulpal and periodontal phenomena at each time of ITM. The microscopic space of the movement was analyzed with the Zeiss® histological ruler and the bone supporting tissue of the MI regarding inflammatory and scarring parameters. Besides that, the relation between the percentage of collagen types I and III was verified through the histochemical reaction of Picrosirius Red after light polarization. A macroscopic analysis showed a small decrease in the control group of the distance from the upper left first molar to the MI with 28 days of orthodontic activation, and the variation in the area of ​​irregular triangles on days 21st and 28th (p<0,05). It was also evidenced, histologically, a significant increase in tooth displacement in the control group on days 21 and 28 (p<0,05). The upper left first molar did not show any significant difference regarding pulp and periodontal phenomena between the groups throughout the analyzed period and the ITM time did not influence the intensity of the alterations in the groups (p>0,05). The epithelial cells of Malassez reduce the reduction in group ZA on the side where there was no ITM and in the control group on the side where there was movement (p<0,05) in relation to the time of orthodontic induction. A significant reduction in the relationship between collagen type I and type III was observed in group ZA on day 14th (p<0,05). The adjacent area to the defected bone promoted by MI insertion showed significantly increased empty osteocyte lacunae in the group ZA on days 14, 21st and 28th and in the area distant from MI on days 21 and 28 (p<0,05), with no relationship related to the disposition of the inflammatory infiltrate (p>0,05). The increase in ITM time did not influence the intensity of the inflammatory process between the groups and the disposition of the inflammatory infiltrate was shown to be diffuse in the group ZA on days 7th and 28th (p<0,05), becoming predominantly neutrophilic on the day 28th. In short, group ZA reduced tooth displacement, not directly interfering with the pulp and periodontal tissue, but in reducing the percentage of malassez of cells when there was no ITM. The administration of the drug did not change the repair process provided by the collagen fibers of the periodontal ligament, but it did change the healing parameters of the MI support bone tissue, probably in association with the trauma of the installation of the anchoring device, without characterizing an osteonecrosis.