The interventions are Scaling and Root Planing (SRP) combined with systemically administered moxifloxacin (MOX) 400 mg, once daily for 7 days.The experimental treatment group consist of SRP combined with systemically administered MOX at the dosage of 400 mg once daily for 7 days.One-stage full-mouth SRP under local anesthesia will be performed (using manual instruments and ultrasonic debridement) in approximately 2 h and half by the same experienced clinician.The endpoint of SRP will be a tactile smooth root surface. The adjunctive agent will start at the SRP visit. Subjects in the MOX group will be extensively informed about the intake of the prescribed medication.

The active comparator is Scaling and Root Planing (SRP) combined with systemically administered Amoxicillin (amox) + Metronidazole (metro) 500 mg tid each one for 7 days. The active comparator group consist of SRP combined with systemically administered Amoxicillin (amox) + Metronidazole (metro) 500 mg tid each one for 7 days.

One-stage full-mouth SRP under local anesthesia will be performed (using manual instruments and ultrasonic debridement) in approximately 2 h and half by the same experienced clinician.The endpoint of SRP will be a tactile smooth root surface. The adjunctive agent will start at the SRP visit. Subjects in the amox-metro group will be extensively informed about the intake of the prescribed medication.

Scaling and Root Planing (SRP) + placebo once daily for 7 days. The placebo comparator group consist of SRP combined with systemically administered placebo once daily for 7 days. One-stage full-mouth SRP under local anesthesia will be performed (using manual instruments and ultrasonic debridement) in approximately 2 h and half by the same experienced clinician.The endpoint of SRP will be a tactile smooth root surface. The placebo agent will start at the SRP visit. Subjects in the placebo group will be extensively informed about the intake of the prescribed medication.

Scaling and Root Planing combined with systemically administered moxifloxacin (MOX) 400 mg, once daily for 7 days

It was defined that the primary outcome variable to determine the superiority of one treatment over the other would be differences between groups for means Clinical Attachment Level changes at 6 months post-treatment. This is a measure assessing change between two time points .