The hypothesis to be tested in this study is whether photodynamic therapy (PDT) could favor the decontamination of these areas, as the photosensitizer and light are capable of reaching areas that these instruments have difficulty accessing. In other words, the objective of this study is to evaluate the impact of PDT as an adjuvant treatment to scaling, considering clinical immunoregulatory in patients with gingivitis with the predisposing factor of the use of a fixed orthodontic appliance. A randomized, controlled, double-blind, split-mouth clinical study will include 17 patients. Patients will have their mouth divided into two groups: Control group (n = 17) - Scaling and Root Planing (SRP) + PDT placebo and Experimental group (n = 17) - SRP + PDT. In G2 will be used methylene blue 0.005%, λ = 660nm, 9J (joule) per inflamed site, irradiance = 3.5W / cm (watts/centimeter), radiant exposure = 318J / cm2. In G1 and G2 the scaling will be performed with the aid of the ultrasound. All participants will receive oral hygiene guidance (OHG) after to the end of the study. The clinical periodontal data to be analyzed: plaque index (PI), gingival index (GI) and probing depth (PD) and clinical level of insertion (CLI) by means of a periodontal probe. Crevicular fluid will be collected (from 8 pre-determined sites) for analysis of the IL-6 (interleukin), IL-1β, IL-8, TNF-α (tumor necrosis factor) and IL-10 cytokines, using the ELISA method.

It is known that the presence of orthodontic brackets predisposes for a change in both the quantity and quality of the biofilm, due to the challenge of brushing adequately. The sites are difficult to access with a toothbrush and periodontal curette, worsening inflammation. In addition, gingival growth is frequently associated with poor hygiene. The hypothesis to be tested in this study is whether photodynamic therapy (PDT) could favor the decontamination of these areas, as the photosensitizer and light are capable of reaching areas that these instruments have difficulty accessing. In other words, the objective of this study is to evaluate the impact of PDT as an adjuvant treatment to scaling, considering clinical and immunoregulatory parameters in patients with gingivitis with the predisposing factor of the use of a fixed orthodontic appliance. A randomized, controlled, double-blind, split-mouth clinical study will include 17 patients, both genders, having used the fixed appliance for more than 12 months, with gingivitis present. Patients will have their mouth divided into two groups: Control group (n = 17) - Scaling and Root Planing (SRP) + PDT placebo and Experimental group (n = 17) - SRP + PDT. In G2 methylene blue 0.005%, λ = 660nm, 9J (joule) per inflamed site, irradiance = 3.5W/ cm, radiant exposure = 318J/ cm2. In G1 and G2 the scaling will be performed with the aid of the ultrasound. All participants will receive oral hygiene guidance (OHG) after to the end of the study. The clinical periodontal data to be analyzed: plaque index (PI), gingival index (GI) and probing depth (PD) and clinical level of insertion (CLI) by means of a periodontal probe. Crevicular fluid will be collected (from 8 pre-determined sites) for analysis of the IL-6, IL-1β, IL-8, TNF-α and IL-10 cyttokines, using the ELISA method. All analysis will be realized using the baseline (T0) and (T1) 30 days after treatment. If sample distribution is normal, the Student T-test will be used to compare the measurement of continuous and dependent variables. If it is not normal, the Mann-Whitney test will be used. The data will be presented in terms of ± PD and the value of p will be defined as 0.05.

Inclusion Criteria:

• healthy participants (negative medical history),
• of both genders,
• aged 10 to 30 years,
• with gingivitis induced by dental biofilm,
• predisposed by the use of a fixed orthodontic appliance, according to the classification of 2018

Exclusion Criteria:

• participants with maxillary and mandibular deformities,
• periodontitis,
• oral lesions and who have used antibiotics for less than 3 months,
• those who have used non-steroidal anti-inflammatory drugs and continuous corticosteroid therapy for less than 3 months,
• who have been using mouthwash in the past 3 months.
• Participants who have modifying factors for periodontal disease, such as diabetics, immunosuppressive smokers (cyclosporine), anticonvulsants (phenytoin), calcium channel blockers (nifedipine) and pregnant and lactating women as well as those who are HIV positive, or have Hepatitis B or C. - Patients who require prophylactic antibiotic therapy for periodontal treatment - who have had periodontal treatment in the last 6 months.
• Patients who have non-biofilm-induced gum disease.
• Patients who for some reason during the study have to initiate the use of the medicines and mouthwashes mentioned above or acquire a disease that is a modifying factor for periodontal disease or become pregnant.
• Patients who do not wish to remain part of the study may drop out whenever they wish.

Only the researcher responsible for conducting the treatments (who will open the randomized envelopes) will know which treatment is assigned to each patient. The identification of each group will only be revealed by this researcher after statistical analysis of the data for all those involved in the study. Therefore, the researcher responsible for data collection, the microbiologist and the statistician will be blind regarding the treatments assigned to the groups. The patient will also be blind to the type of treatment performed since the periodontal treatment will be identical in both groups and treatment with PDT will be simulated in the control group.