Study Objectives and Purpose The purpose of this study is to assess the clinical efficacy of a new dentifrice, containing carbonate/hydroxyapatite nanocrystals (BioRepair®, Kurt Wolff, Bielefeld, Germany), in subjects suffering from severe gingivitis and/or mild to moderate chronic periodontitis and receiving non-surgical periodontal therapy. Clinical efficacy will be evaluated regarding clinical and microbiological parameters and compared to the use of a zinc-fluoride containing dentifrice (Meridol®, GABA, Lörrach, Germany) serving as a positive control.