## 4 Discussion  
In this prospective pilot study, we investigated how CAT could affect severe periodontal conditions in perio patients with pathologic tooth migration (PTM), previously treated with non-surgical and surgical periodontal treatments. An interdisciplinary approach, combining periodontal and orthodontic treatment, is needed to re-establish proper esthetics and function in stage IV periodontitis patients with PTM [27; 28]. Application of orthodontics forces requires complete inflammation removal \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**Clinical Crown** & & & & & \\
**Size (mm)** & **Time** & **Estimate** & **Std.Error** & \(p\) **Value** & **95\% Lower** & **95\% Upper** \\ \hline Anterior Teeth & T2 & 0.2 & 0.18 & 0.28 & \(-\)0.16 & 0.55 \\ (incisors, cuspids) & & & & & \\ Posterior Teeth & & & & & \\ (premolars, molars) & T2 & 0.29 & 0.15 & **0.049** & 0.001 & 0.57 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Scan digital data measurements. Multiple regression analyses stratified per teeth. T1 was used as reference. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**Pixel Color** & **Time** & **Estimate (Pixel Number)** & **Std.Error** & \(p\) **Value** & **95\% Lower** & **95\% Upper** \\ \hline \hline BLUE & T2 & 18,084 & 16,015 & 0.27 & \(-\)13,305.58 & 49,473.48 \\ GREEN & T2 & 1046.7 & 1854 & 0.58 & \(-\)2587.11 & 4680.59 \\ RED & T2 & \(-\)7117 & 2764 & **0.0144** & \(-\)12,534.14 & \(-\)1700.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Occlusal contact areas were measured as the difference in number of differently colored pixels, at the beginning (T1) and at the end (T2) of the orthodontic treatment. Multiple regression analyses are stratified by color. T1 was used as reference. and a strict oral hygiene protocol. Indeed, all patients underwent orthodontic therapy at the end of the active periodontal treatment and followed a strict periodontal maintenance program [29]. As previously observed in a study carried out on aggressive periodontitis patients [30], orthodontic treatment could lead to a slight improvement in some periodontal outcomes. Moreover, teeth alignment and leveling facilitate hygiene procedures, giving the option to access all teeth surfaces and maintain good oral health easily [18; 31; 32]. Our results showed the maintenance of good periodontal health at the end of orthodontic treatment with clear aligners in the short term. In addition, forces and strengths were applied widely within 1 N limits, mainly on periodontally compromised teeth [33]. Considering all these aspects together is essential to avoid further damaging effects on periodontal tissues due to orthodontic-induced inflammation [34]. Previous studies have displayed satisfactory clinical results with aligners, showing a good percentage of randomly chosen cases compiled with the American Board of Orthodontics-Objective Grading System (ABO-OGS) score [35] when treatments were conducted by expert clinicians [36; 37]. A recent systematic review with meta-analysis [38] compared the outcomes of CAT compared to braces; it showed robust evidence, based on \"ABO scores and proportion of treated cases with 'acceptable' finishing quality (ABO-OGS score \(<30\))\", and did not favor aligners treatment. However, focusing our attention on PTM, ABO components such as alignment, marginal ridges, and interproximal contacts produced very similar results for both CAT and fixed braces appliances. Conversely, the same systematic review and meta-analysis based on the PAR index, revealed no significant differences between aligners and braces, with the exception of significant differences in the PAR components for the upper anterior and overbite, which favored braces [38]. On this basis, CAT would seem not to severely worsen periodontal indices with respect to the end of the periodontal treatment, contributing to reduced PPD in the anterior and posterior areas with periodontal maintenance therapy [39; 40].