A balanced random permuted block approach will be used to prepare the randomization tables in order to avoid unequal balance between 2 treatments. In order to reduce the chance of unfavorable splits between test and control patients in terms of key prognostic factors, the randomization process will take into account the following variable: smoke. Treatment assignment will be noted in the registration and treatment assignment form that will be kept by the central registrar. To conceal assignment from the investigator until the time, at the end of the non-surgical periodontal therapy the central registrar will instruct the investigator to assign a sealed envelope containing the treatment for each patient, every envelop is endowed of a Treatment's Code, composed by a letter (that corresponds to the clinical center) and two numbers.