## 4 Discussion
This review is consistent with the literature regarding the effectiveness of the use of ultrasonic and/or manual instruments in nonsurgical periodontal therapy, even without additional therapies. The main limitation of this review is the heterogeneity of the included studies with respect to the treatment modality used: not all studies evaluated the effectiveness of the same type of curette or the same type of ultrasonic scaler; moreover, it must be taken into account that each clinician often uses a combination of the two tools in daily practice. Given the different views on tissue damage or surface roughness [81; 82; 83; 84; 85; 86; 87; 88; 89], it maybe hoped that an ultrasonic scaler with perio-slim inserts that fit the periodontal pocket will be used to remove most deposits, thereby attempting to reduce the use of manual instruments. In addition to the specification of the type of heterogeneous instrumentation, another limitation is that the included studies have not evaluated the same degree of periodontal disease, but, still, the use of ultrasonic instrumentation, reducing the use of curettes to the necessary amount, would seem to be the best clinical alternative. This review is unprecedented in that it compares all the instruments and techniques currently available for periodontal treatment, enhancing the skills of the operator and evaluating additional therapies for proper patient management. For future research and RCTs, it would therefore be good to choose the same type of instrumentation for nonsurgical periodontal treatment at the same stage of the disease and also to assess whether there is a difference in terms of the cost and adverse effects (such as root sensitivity and patient pain/comfort) between the proposed treatments, in order to provide the operator with the choice of treatment. In certain cases, the use of additional therapies in addition to scaling and root planing may be the best way to improve tissue recovery. In fact, some of the studies considered suggested that the use of lasers could be beneficial in terms of the probing pocket depth, clinical attack loss and bleeding on probing [28; 30; 32; 33; 34; 35; 37; 39; 43; 44; 45; 48]. This is supported by the literature [89], which shows short-term results, but the long-term benefits are still unknown [90]. As the studies included in the reviews and meta-analyses that are now available are heterogeneous, it would be helpful to know what type of laser and wavelength to use [91]. Ozone is a powerful disinfect that has been used in dentistry for a number of years, but it does not appear to provide significant improvements over standard nonsurgical periodontal therapy alone [14; 49; 50; 53; 54]. Further studies are needed to determine whether it can be a useful treatment for periodontal disease. Finally, the use of powders may be useful in the removal of subgingival biofilm, favoring a reduction in the probing pocket depth, as has been demonstrated in the literature [92]. Currently, no treatment is better than another in addition to nonsurgical periodontal treatment; it is necessary to evaluate the possible therapy according to the condition and needs of the patient.