The present study was designed as a prospective controlled study focusing on the effect of oral hygiene instructions and periodontal nonsurgical treatment( PNST) on clinical outcomes and patients related outcomes (PROMs) in smokers versus former smokers versus non smoker patients.

75 consecutive patients presenting chronic periodontitis and who needed periodontal treatment were recruited in the Department of Periodontology and Oral Surgery at the University Hospital of Liège, Belgium (CHU, Sart-Tilman) according to the inclusion criteria.

The patients were subdivided between three groups: non-smoker (25), former smoker (25), and smoker patients(25).

Patients received informations about periodontitis genesis, the demonstration of oral hygiene instructions (OHI), the goal of PNST and the follow-up time were given ( baseline, after OHI, 3 months after PNST).

Periodontal clinical parameters and PROMS were collecetd and compared between 3 groups, at each visit.

Data collection:Periodontal clinical measurements and PROMS

The periodontal examination was conducted by a single periodontist (L.S) and included: probing depth (PD), gingival recession (RD), clinical attachment level (CAL), bleeding on probing (BOP), plaque score index (PI), Furcation (Furc), tooth mobility , the percentage of sites of PD ≥ 6mm and the number of missing tooth was recorded A graduated manual periodontal probe was used to take measurements at the 6 sites of each tooth. BOP (%) and plaque score (%) were collected as well as tooth mobility with a score from 1 to 3 . The furcation impairments were diagnosed with a Nabers probe according to the classification of Hamp and the Inflamed Surface Area (PISA) was calculated. Patients were classified according to the new periodontal classification identifying the grade, the stage and the extend of the periodontitis.

Patient-reported outcome measures (PROMs) A questionnaire using a visual analogue scale (VAS) was given to all participants regarding their oral hygiene habits, and perception about oral esthetic. The following questions were subjected to the patients: nine questions graduated scale from 0 to 10: 1/"How do you judge your degree of oral hygiene?", 2/"What is the frequency of utilization of interdental brushing?", 3/"Do you like the color of your teeth? , 4/"Your teeth are there sensitive to cold? , 5/ "How do you judge your degree of gingival health? , 6/ "How do you judge the esthetic aspect of you gum?", 7/ "Do you like the color of your gum? ", 8/ "Does your gum bleed during brushing?", 9/ "How do you judge your breath?".

sample size: The study was powered to detect a minimum clinically significant difference in probing depth (PD) of 0.5 mm between patients, using α= 0.05. The probing depth at baseline was considered covariate.

Inclusion Criteria:

• aged of minimum 18 years old
• chronic periodontitis
• presence of a minimum of 6 teeth at each arch
• a minimum of 6 teeth with pocket depth of 5 mm
• signed the informed consent

Exclusion Criteria:

• aggressive periodontitis
• diabetes
• connective tissue disease
• pregnancy
• radio-therapy
• chemotherapy
• psychological disease
• previous periodontal therapy