The aim of this clinical trial is to evaluate photodynamic therapy and photobiomodulation in the periodontitis treatment. To evaluate the clinical and microbiological response of conventional periodontal treatment associated with photodynamic therapy and photobiomodulation with red or infrared laser.

Participants will receive periodontal treatment carried out with the use 0.005% methylene blue and laser therapy (photodynamic therapy), associated with conventional periodontal treatment, as well as the use of photobiomodulation with red or infrared laser associated with conventional periodontal treatment in participants with periodontitis. So, twenty periodontitis patients will be selected and separated in two groups compared with placebo. Clinical and microbiological parameters will be evaluated at baseline and 3 months after periodontal treatment: plaque Index, bleeding on probe, probing depth, gingival recession and clinical attachment level.

Periodontitis is a chronic, inflammatory and multifactorial disease, caused by an interaction between debiotic biofilm and its products and an exacerbated host response, leading to the progressive destruction of the supporting periodontium (bone, cement and periodontal ligament), causing loss of clinical attachment. and radiographic, bleeding on probing and periodontal pocket formation. Periodontal disease has a high prevalence and is one of the main causes of edentulism, with a great negative impact on chewing function, aesthetics and quality of life related to oral health. It is, therefore, considered a serious public health problem.

Conventional periodontal therapy consists of scaling and root planing (SRP) and control of supragingival plaque, but in some cases it has been shown to be ineffective in treating periodontitis, especially in difficult to access areas such as furcations and deep pockets. These cases benefit from adjuvant therapies, such as laser therapy, to help heal periodontal tissues, reduce microorganisms and improve clinical parameters.

Photobiomodulation and photodynamic therapy have been widely applied in the treatment of periodontal disease, due to their clinical, cellular and bactericidal effects. When associated with conventional periodontal therapy, its benefits increase, promoting a significant reduction in probing depth, number of deep pockets and bleeding. Furthermore, significant reduction of periodontopathogens and Candida albicans can be observed in the literature after photobiomodulation and photodynamic therapy.

Despite the benefits found when different laser therapy protocols are used in periodontal treatment, due to the lack of studies with high methodological quality and weak evidence in the existing literature, more studies are needed to prove their effects, establish appropriate protocols and evaluate the antimicrobial potential in periodontopathogens, which remains debatable, as recent systematic reviews point out.

The direct benefits of this study are the treatment of periodontal disease for the participants and for the scientific community to indicate new forms of periodontal therapy using different protocols of laser therapy associated with periodontal instrumentation. All tooth pocket sites in all groups will receive treatment.

Inclusion Criteria:

• Adult participants with periodontal disease;
• Four or more periodontal sites with PPD≥6 mm and CAL≥5 mm, non-adjacent;
• Generalized periodontitis, with more than 30% of the sites involved (Caton et al., 2018);
• Stages III and IV of periodontal disease (Caton et al., 2018);

Exclusion Criteria:

• Participants with hypersensitivity to the components of the 0.005% methylene blue gel;
• Received periodontal treatment in the last six months;
• Drugs (alcoholics, use of anti-inflammatories and antibiotics in the last 3 months);

Any evidence of systemic modifying factors which may directly interfere with the completion of the work (bias), such as:

• Pregnant and breastfeeding women;
• Hormone replacement therapy;
• Smoking;
• Hyperglycemia;
• Osteoporosis;
• Diagnosed with HIV+ or AIDS.

The result will be communicated verbally to each participant.

Randomization will be carried out by a blind clinician for the initial assessment of participants, using a computer program (Spyder 5.5.4), in which each patient will be randomly selected to define the site to receive one of the treatments. Next, gels will be encoded in a syringe and applied by a researcher blind to the sites and reagents, each of the 4 sites will receive one of the following treatments: 1 - photosensitization with 0.005% AM gel (Fórmula e Ação Farmácia, São Paulo, SP, Brazil) for 5 minutes, and apply photodynamic therapy with a red laser; 2 - photobiomodulation with red laser; 3 - photobiomodulation with infrared laser; and 4 - control, application of saline gel and, after 5 minutes, simulate the application of the laser, with the device in inactive mode, in order to maintain blinding of the patients (control). In groups 2 and 3, as no gel will be applied, the application of the gel with an empty syringe will be simulated, to keep patients blind