This work describes the therapeutic protocol of combined orthodontic-periodontal treatment and evaluates the effectiveness of surgical and nonsurgical periodontal therapy in the maintenance of a healthy periodontal status after the orthodontic treatment. Surgical periodontal treatment was performed in 267 patients affected by severe periodontal disease, and 128 patients had nonsurgical treatment. For each patient the mean value of probing depth (mPPD) and the rate of positive bleeding on probing (%BoP) of the teeth involved in the orthodontic movement were registered before the start of the periodontal treatment, at the end of the orthodontic treatment, and 2, 4 ,6, 10, and 12 years after the end of the orthodontic treatment. Comparison between pretreatment and posttreatment values and between pretreatment and follow-up values showed a decrease in mPPD and %BoP that was of statistical significance. The difference between posttreatment and follow-up values was not statistically significant. These results suggest that orthodontic treatment is no longer a contraindication in the therapy of severe adult periodontitis. In these cases orthodontics improve the possibilities of saving and restoring a deteriorated dentition.