If the treatment objectives are not achieved or are only partly achieved following non-surgical periodontal therapy, the next step is surgery. The goal of periodontal surgery is primarily to facilitate cleaning of the root surface under direct vision. In addition, soft tissue and bone pockets can be eliminated surgically using resective techniques or defects filled/regenerated using regenerative techniques, the ultimate goal being the re-establishment of physiological morphology. In the presence of very deep pockets and extensive bone defects or furcation involvement in particular, adequate removal of plaque niches can often take place only after opening of the area concerned. Adjunctive treatment with systemic antibiotics based on a microbiological analysis also covers periodontitis-associated bacteria located in deeper soft tissue and outside the sulcus.