Objective: The aim of the present systematic review was to evaluate the periodontal tissue inflammation indexes in patients undergoing different orthodontic treatment. Method and Materials: The Cochrane Oral Health Group specialist trials, Medline, and Embase databases were used for the research. All the included studies had to report bleeding on probing (BOP) depth as primary outcome. Changes in probing depth, clinical attachment level, Gingival Index, and Periodontal Index were included in the review as secondary outcome measurements. Results: Ten studies reporting on 421 patients and different types of orthodontic treatment were selected for the analysis. Owing to the heterogeneity of studies present in the literature, it was not possible to perform a meta-analysis. Conclusion: Within their limits, the results showed an increase of periodontal parameters after orthodontic treatment, indicating that it influences the accumulation and composition of the subgingival microbiota and subsequently induces more inflammation and higher BOP. Keywords: bleeding on probing depth, orthodontic appliance, orthodontic treatment, ortho-perio, periodontal inflammation