###### Abstract  
Pathologic tooth migration (PTM) is a complication of Stage III and IV periodontitis. This pilot study aims to analyze the periodontal response to orthodontic aligner therapy in stage IV periodontitis patients, by perio charting and digital orthodontic data obtained from intraoral scans. Following periodontal treatment of 21 recruited patients, 11 underwent clear aligner treatment. Periodontal data (Probing Pocket Depth--PPD, Recession Index--REC, Clinical Attachment Loss--CAL) were collected at baseline (T0), after periodontal treatment (T1), and at the end of the orthodontic treatment (T2). Digital data obtained at T1 and T2 were processed with the 3D software Geomagic(r) Control X(tm). Ocuslograms obtained by the proximity sensors of the scans were converted into differently colored pixeled areas. These results were compared to highlight changes in clinical crown length or occlusal contact areas. The results showed a slight increase in the REC index and a statistically significant reduction of PPD and CAL at T1 and T2. Digital data showed a statistically significant decrease in terms of gingival recessions and clinical crowns at the end of orthodontic treatment. Hard occlusal contacts showed a statistically significant decrease by the end of the orthodontic treatment. The results are comparable to those reported in the scientific literature for fixed orthodontic treatment. Clear aligner treatment could be considered an option in patients with severe periodontitis, promoting final light occlusal contacts. clear aligners; periodontal index; occlusal contacts; tooth movement +
Footnote †: journal: Medical Sciences  
0000-0001-8891-4000]S.R.R.S. Orthodontics is a component of the multidisciplinary treatment of periodontitis aims to re-establish the correct position of flared teeth to restore esthetics and function [7]. Despite the absence of a direct correlation between malocclusion and periodontal breakdown [8], orthodontic treatment is recommended when periodontal health can be worsened by severe crowding, premature contacts, deep bites associated with direct trauma of the periodontal tissues, excessive mobility due to lip interposition [9; 10; 11], and premature contacts with occlusal instability [12; 13]. Orthodontic forces on the periodonotally compromised tooth produce different effects when compared to teeth with an intact periodontium, since the tooth's center of resistance shifts apically, often leading to alveolar bone loss [14], and the moment-to-force ratio for orthodontic tooth movement (OTM) increases with the severity of bone resorption. Controlled tooth movements and appropriate force systems must be delivered according to each individual's anatomic situation. Moreover, it has been demonstrated that the application of light force with a clear aligners system, results in a small amount of linear and angular displacement, even if the predictability of small horizontal, vertical, and sagittal orthodontic movements is likely to occur [15]. Aligner treatment, moreover, reduces posterior occlusal contacts [16], but this condition might not be favored in patients with anterior flaring. However, it is mandatory that plaque-induced inflammation be completely suppressed before the application of orthodontic forces, and that proper oral hygiene is maintained [17]. The use of clear aligners may minimize orthodontics-related negative effects on periodontal health, facilitating proper oral hygiene procedures [18], allowing better maintenance of good gingival conditions than fixed appliances [19] and not inducing significant changes in the composition of oral microbiome in the short term [20]; thus, they might be recommended for patients at high risk of developing periodontal issues. Therefore, this prospective pilot study was conducted to test periodontal indexes in Stage IV periodontitis patients treated with aligner orthodontics as a primary outcome.