## 4 Discussion  
There has been a noticeable increase in the number of adults undergoing orthodontic treatment, particularly CAT, in recent years due to rising health standards and expectations of the adult population. A significant proportion of adults seeking orthodontic treatment have had already undergone orthodontic treatment in their childhood and adolescence. A thorough clinical assessment and treatment planning are required prior to CAT, including understanding the patient's motivation for seeking CAT, their medical history, reviewing orthodontic findings and assessing the need for treatment procedures such as IPR. To date, little research has examined whether patients' motivations for seeking CAT, sociodemographic parameters, and treatment planning and duration differ between first-time and re-treatment patients with a history of orthodontic treatment. The aim of this study was to evaluate the outcomes of CAT and patient demographics of patients seeking orthodontic re-treatment who had previously received orthodontic treatment in childhood or adolescence. It aimed to compare CAT on a sample size comprised of 2080 patients (493 were re-treatment patients and 1587 were first-time patients) in terms of treatment duration, patient profiles, associated socio-demographic or other variables, and patient satisfaction. Although the two groups were not matched for gender and age, statistical analysis showed that both the re-treatment and first-treatment groups were well-matched for age and age group distribution. To the authors' knowledge, this is the first real-world study to compare clear aligner treatment of re-treatment patients with a control group on a larger scale. Using real-world data and a retrospective design, we aimed to provide insight into real-world scenarios to support clinical decision-making. Our findings require detailed discussion and interpretation within the limitations. First, in the present sample, it was found that patients in both patient groups were on average under 30 years of age and the majority were female. In particular, the proportion of females in the re-treatment group was significantly higher than in the first-treatment group, with a higher proportion of females undergoing re-treatment than males. In line with previous research, gender was found to be associated with the likelihood of seeking re-treatment, with a higher percentage of females seeking re-treatment than males [12]. Furthermore, it has been reported that females consider straight teeth to be more important than males, leading them to opt for re-treatment to improve their self-perception of dental \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Beginning of Treatment**} & \multicolumn{2}{c}{**After Clinical Visit**} & \multicolumn{2}{c}{**During Treatment Course**} \\ \hline \multicolumn{5}{c}{**Previous Orthodontic Treatment**} \\ \hline
**YES** & **NO** & **YES** & **NO** & **YES** & **NO** \\ \hline Mean Score & 4.38 & 4.35 & 4.56 & 4.39 & 4.2 & 4.04 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Treatment satisfaction scores by previous orthodontic treatment. appearance [19; 20]. In addition, girls have been found to be treated more frequently than boys in childhood [1; 2], which may lead to more females experiencing orthodontic relapse due to the frequency of previous orthodontic treatment. Second, the results of the present study suggest that the main motives for undergoing CAT and patient satisfaction during CAT did not differ between re-treatment and first-time patients. Most of the patients indicated that crowding was the primary motive for seeking CAT, followed by protruding teeth in both groups. Accordingly, crowding was found to be the most common malocclusion trait in both genders. For example, [PERSON] et al. [21] reported that a high percentage of patients presented with dental crowding, with a prevalence of up to 84.4%.