In some practices, it is common for the Winkelhoff cocktail (combining metronidazole and amoxicillin) to be prescribed indiscriminately for periodontal therapy. Without knowledge of the microbial spectrum, this can mean overtreatment for many patients, however, because single-agent antibiotic therapy would often be sufficient. According to a statistical analysis of almost 170,000 patient specimens (micro-IDent®, Hain Lifescience, Nehren), combination treatment with the Winkelhoff cocktail is actually indicated only in 23.67% of the cases analyzed. Adjunctive treatment with metronidazole would be ideal for the vast majority of patients (68.59% in fact). In other cases, the dentist might decide against antibiotic therapy despite the fact that this would be strongly recommended. A microbiological analysis with micro-IDent® or micro-IDent®plus makes it possible to avoid such errors and thus provides an important decision-making tool for effective treatment planning.