Aim of this study:

is to evaluate the influence of stress level on the response of non surgical periodontal therapy in patients affected by severe periodontitis divided into "Medium/High stress level" or "Low stress level" based on the Perceived Stress Scale (PSS). The defined primary outcome referring to the clinical response of the patients is the bleeding index, Full-Mouth Bleeding Score (FMBS), as a clinical sign of inflammation.

Materials and Methods:

Monocentric prospective triple blinded study. A single evaluator conducting all the psychologic tests, a single operator blinded to the results of the psychologic tests doing all the clinical measurements, and the patients will be initially blinded to the category of stress that they'll belong to. The minimum number of patients to enrol will be 89 based on a sample calculation.

Inclusion Criteria:

Patients must meet all of the following inclusion criteria to be eligible for enrollment into the study:

Age from 20 to 80 years Diagnosis of Periodontitis stage III/IV according to the new classification (2018); Presence of at least 14 teeth, with a minimum of 10 sites with PD at least > 5 mm and radiographic evidence of alveolar bone loss.

Written informed consent

Exclusion Criteria.

The presence of any of the following will exclude a subject from study enrollment:

Smokers > 10 cig/die Patients with orthodontic appliances; Pregnant or lactating women; Individuals who have received periodontal treatment in the 6 months prior to recruitment; Patients with systemic diseases that could interfere the clinical response to periodontal treatment (i.e. diabetes); Subjects under treatment with antibiotics, steroidal and/or non-steroidal anti-inflammatory medication 3 weeks prior to the visit and patients treated with antiepileptic drugs

Operative procedure:

Clinical parameters and psychologic test will be done at the baseline. All the patients will be treated by means of non surgical periodontal therapy on a quadrant protocol including oral hygiene instructions and motivations and subgingival instrumentation in four successive visits. 6 weeks after the last visit, the clinical parameters will be registered again.

Clinical Parameters:

Periodontal condition of each patient will be evaluated through the collection of the following parameters:

• Full-Mouth Bleeding score (FMBS): presence/absence of bleeding on probing using a periodontal probe on each surface of the tooth (six sites per tooth), calculated in percentage for all the examined teeth.
• Full-Mouth Plaque Score (FMPS): presence/absence of plaque using a periodontal probe on each surface of the tooth (six sites per tooth), calculated in percentage for all the examined teeth.
• Probing Depth (PD): measured for each surface of the tooth (six sites per tooth) using a periodontal probe, measured as the distance between the cementoenamel junction (CEJ) and the depth of the pocket.
• Gingival recession (Rec): measured for each surface of the tooth (six sites per tooth) using a periodontal probe, measured as the distance between the cementoenamel junction (CEJ) and the free gingival margin.
• Clinical attachment level (CAL): The sum of PD and Rec.

Psychologic Test:

The Stress condition of each patient will be assessed by a Psychologist using:

PSS is a 10-items self-report questionnaire that measure the degree to which situations in one's life are appraised as stressful. The PSS is scored on a 5-point scale (never, almost never, sometimes, fairly often and very often). PSS norms are available from a sample of the USA collected by Cohen & Williamson (1988). The mean level for men was 12.1 (S.D. 5.9) and for women 13.7 (S.D. 6.6).

Inclusion Criteria:

• Diagnosis of Periodontitis stage III/IV according to the new classification (2018);
• Presence of at least 14 teeth, with a minimum of 10 sites with PD at least > 5 mm and radiographic evidence of alveolar bone loss.
• Written informed consent

Exclusion Criteria:

• Smokers > 10 cig/die
• Patients with orthodontic appliances;
• Pregnant or lactating women;
• Individuals who have received periodontal treatment in the 6 months prior to recruitment;
• Patients with systemic diseases that could interfere the clinical response to periodontal treatment (i.e. diabetes);
• Subjects under treatment with antibiotics, steroidal and/or non-steroidal anti-inflammatory medication 3 weeks prior to the visit and patients treated with antiepileptic drugs.