The purpose of this study is to analyze histomorphometrically and, also through immunohistochemical reactions, the influence of Low-Level Laser Therapy (LLLT) and Photodynamic Therapy (PDT) as adjuvant to conventional mechanical treatment of experimentally induced periodontal disease in female rats with depletion of estrogen and under systemic influence of nicotine. 360 rats will be divided into 4 groups: Group A - normal; Group B - normal treated with nicotine; Group C - ovariectomized; Group D - ovariectomized treated with nicotine. The animals of groups B and D will receive daily subcutaneous injections of nicotine beginning 30 days before the induction of experimental periodontitis (EP). The animals of groups C and D will undergo bilateral ovariectomies 21 days before the induction of EP. The EP will be induced by the adaptation of a cotton ligature in a submarginal position around the mandibular left first molar. The ligature will be removed after 7 days and the animals will be divided into subgroups according to the following local treatments: I - Scaling and root planing (SRP) and irrigation with saline; II - SRP and irrigation with saline combined with LLLT; III - SRP and irrigation with 1 ml of Toluidine Blue-O (TBO) followed by an application of low-level laser (PDT). Ten animals of each subgroup will be euthanized at 7, 15 and 30 days after the local treatment. The specimens will be embedded in paraffin. Semi-serial sections (4 µm) will be obtained in a mesio-distal direction and stained with either hematoxylin and eosin or Masson's Trichrome. Bone loss in the furcation region will be analyzed histomorphometrically and also through immunohistochemical reactions. The data will be submitted to statistical analysis.
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