Efeito da combinação do laser de baixa intensidade e do ranelato de estrôncio na reabsorção óssea alveolar induzida por ligadura em ratos

Abstract

Chronic periodontitis is characterized by an infectious and inflammatory processes where there is impairment of periodontal supporting tissue: connective tissue, cementum and alveolar bone. In recent years the science has evolved rapidly and new therapeutic approaches in the dental arise through the use of lasers as well as different pharmacological approaches, such as strontium ranelate (SrR), a drug used to treat osteoporosis that is noted for its double effect on bone metabolism, antirreabsortive and bone anabolic. The aim of this study was to evaluate the effect of low level laser therapy (LLLT) combinated with Strontium Ranelate (SrR) in alveolar bone resorption (ABR) ligature-induced in rats through introductory review of literature on the effects of laser low intensity (LLLT) in periodontal tissues as of preclinical studies and clinical trials demosntraram action LBI in microcirculation, periodontal tissue components and inflammatory mediators, using the PubMed database and the keywords low Level Laser Therapy , Periodontal and Periodontal tissues combined with each other, with publication publication from the year 2000 to March 2015, followed by an assessment of the inflammatory response of LBI through standard models of inflammation and evaluation of the combination of LLLT and SrR on alveolar bone resorption (ABR) ligature-induced in rats. It was observed that LLLT may assist in the periodontal healing process. To investigate the inflammatory response, we used paw edema and peritonitis models, both induced for carrageenan (Cg 700μg) intraplantar and intraperitoneal administration, respectively. The animals were divided in groups (n = 6/each) received prior to carrageenan injection, Saline (SAL 0.9% NaCl; vo), Dexamethasone (DEXA 1 mg/kg-sc) and LLLT irradiation (100 mW; 7 J/cm2). In peritonitis model one group of animals not handled (Normal) was added. Edema was calculated by the volume of fluid displaced (ml) by the inflammatory stimulus paws before and 1, 2, 3 and 4 h after, moreover plantar tissue was collected for analysis of MPO activity. After the 4th hour of peritonitis, the rats were sacrificed to collect the peritoneal fluid and evaluation of neutrophil migration. The ABR was induced by ligature around the upper second molars of animals (n= 6/each) receiving preliminarily LLLT (660 nm, 100mW) at different doses (2, 4 and 8 J/cm2) or SAL for 14 days and from the better dose found (4 J/ cm2) to prevent ABR, it was chosen to observe the effect of the LLLT on ABR with or without removal ligature from 7th day. In addition, we evaluated the effect of the combination of LBI (4 J/cm2) with SrR (630 mg/kg). After sacrifice on the 14th day, blood samples collected up to bone alkaline phosphatase analysis (BALP), gingival tissue was removed for evaluation of MPO activity and expression of IL1-β by ELISA, and maxillae was removed to evaluate ABR by morphometric and histopathologic analysis. In addition, immunohistochemistry was performed to detect TRAP and RANKL. From the review of 23 selected articles, 2 have shown increased amount of blood vessels and a decrease in another, the LBI does not alter the diameters of blood vessels and 1 showed that LLLT increased hyaline areas, Other 9 demonstrated that LLLT may increase the components (fibroblasts, osteoclasts, mast cells, fibronectin, collagen type I epithelial cells, cells of the periodontal ligament) tissue related periodontal tissue healing, and 9, the LBI reduced inflammatory mediators such as MMPs, TNF-α, IL-6, IL-8, IL-1β, IFN-γ, RANKL TIMP-1, iNOS, iNOS, COX-2 which showed a promising action LBI in periodontal tissues. The use of LLLT confirmed its anti- inflammatory effect by reducing (p<0.05) paw edema (SAL= 1.21 ± 0.19; LLLT= 0.91 ± 0.08), MPO activity in plantar tissue (SAL= 8.97 ± 1.38; LLLT= 5.36 ± 0.39) and neutrophil migration to the peritoneal cavity (SAL= 18.91 ± 3.17; LLLT= 9.33 ± 1.78). The LLLT also reduced (p <0.05) MPO activity in gingival tissue in ROA ligature-induced for 14 days and prevented (p <0.05) ROA with (46%) or without (40%) the ligature removal after 7 days. The treatment with LLLT, SrR and LLLT + SRR reduced (p <0.05) ROA 45.9%, 49.7% and 70.4% respectively, and these results corroborate the histological analyzes of the region between 1º and 2º molar, and histometric furcation region of the 2º molar. Furthermore, treatment with LLLT, SrR and LLLT + SRR reduced (p <0.05) MPO activity in 6ªh (Normal= 0.6±0.1; SAL= 11.7±1.0; LLLT= 5.4±1.1; SrR= 5.9±0.5; LLLT+SrR= 4.5±0.5) and LLLT + SrR reduced (p <0.05) IL- 1β levels (Normal= 12.0±0.7; SAL= 17.5±1.7; LLLT= 17.1±1.1; SrR= 16.0±1.8; LLLT+SrR= 13.3±1.0). All treatments reduce immunostaining for TRAP and RANKL. There was no change in serum BALP, in kidney, liver and spleen indexes, and neither in body weight variation of animals treated with LLLT, SrR or combination LLLT + SrR. It was concluded that LLLT has anti-inflammatory action on periodontal tissues and inflammatory models induced carragegina, prevented alveolar bone resorption induced by ligation. Also it demonstrated synergistic effect when combined with the SrR, prevention ROA, where the reduction of proinflammatory cytokines appears to be essential for this purpose, and may play an important role in inflammatory processes in bone resorption such as occurs in periodontitis.