Influência da terapia fotodinâmica antimicrobiana sobre o colágeno e o status oxidativo gengival em modelo experimental de periodontite em ratos

Abstract

The objective of this study was to evaluate the influence of antimicrobial photodynamic therapy (PDT) with methylene blue (MB) dissolved in 20% ethanol, used as an adjunct to scaling and root planing (SRP), for the treatment of periodontitis in bone loss, collagen fibers and gingival oxidative damage in rats. Seventy male Wistar rats were randomly assigned to five experimental groups according to periodontal treatment: NC (negative control, no periodontitis. n=11); PC (positive control; periodontitis without any treatment. n=11); SRP (Periodontitis and scaling and root planning. n=16), aPDT I (periodontitis and SRP + aPDT + MB solubilized in water. n=16) and aPDT II (periodontitis and SRP + aPDT + MB solubilized in 20% ethanol. n=16). Periodontitis was induced by placing the ligature around the right first molar of all experimental groups, except the NC group. Periodontal treatments were performed after 7 days of ligation removal. At 7 and 15 days after ligature removal, the animals were euthanized and the mandible and gingival samples were collected for histological and biochemical evaluation. The PC and SRP groups presented higher levels of gingival lipoperoxidation at 7 days, but only the PC group presented higher gingival lipoperoxidation on the 15th day compared to the NC group. In addition, the aPDT II group showed a protective action on the gingiva as early as 7 days after the removal of the ligature observed by the maintenance of reduced glutathione levels (GSH), which was similar to the NC group. aPDT was able to prevent the degradation of gingival collagen as early as day 7. The collagen area was negatively correlated with the levels of lipoperoxidation in the gingiva in all groups. The solubilization of the AM in water/ethanol solution prevented the lipid peroxidation and collagen degradation periodontitis-induced in the evaluated times in a short-term. Hypothesi, considering that the periodontitis and the consequent oxidative status in gingiva were modified by aPDT, it is possible that these physiological changes are related hormesis.