Objectives: This randomized clinical trial will compare the usefulness of pre- and postoperative antibiotics while strict asepsis will be followed during periodontal surgery in smokers diagnosed with Stage III Grade C Generalized Periodontitis.

Material and Methods: Two groups of 40 consecutive patients each with fully or partially edentulous jaws will be enrolled. Antibiotics group (GrAB+): will receive oral doxycycline 200 mg, 1 h pre-operatively and 100 mg g for 9 days post-operatively. Non-antibiotics group (GrAB- ): will receive a placebo (no antibiotics). Bacterial samples will be taken from the peri-oral skin before and at the end of the surgery. In 12 patients in each group, samples will also be taken from the nares. A visual analogue scale will evaluate symptoms of infection/ inflammation by both the patient and the periodontist at suture removal.

Inclusion Criteria:

• smoker
• in need of dental implant therapy
• above 18 years of age

Exclusion Criteria:

• allergy to doxycycline,
• need for endocarditis prophylaxis,
• any systemic or local immunodeficiency,
• uncontrolled diabetes mellitus,
• previous radiation therapy in the head and neck area