## 4 Discussion  
The deformation behavior of clear aligner systems is a critical aspect of orthodontic treatment, impacting the efficacy and comfort of aligners. The present study aimed to investigate the deformation behavior of three different aligner systems--CA(r) Pro+ Clear Aligner (Scheu Dental, Iserlohn, Germany), Taglus Premium (Taglus Company, Mumbai, India), and Spark Trugen (Ormco Corp., Orange, CA, USA)--under compression, using the digital image correlation (DIC) technique. The null hypothesis posited that no significant differences in deformation behavior would be recorded among these systems. A study conducted by [PERSON] et al. investigated the mechanical behavior of PET-G-based aligners using DIC under compression testing [14]. The study found that the DIC technique efficiently captured the deformation phases of the material, providing detailed information on the response of the aligners to mechanical loads. This study supported the use of DIC in evaluating the mechanical behavior of aligners thus motivating our approach. Another research explored the use of DIC to measure the displacement and deformation of aligners during orthodontic treatment [15]. The study confirmed that the DIC technique has demonstrated its effectiveness in capturing the mechanical behavior of aligners, highlighting the distribution of displacement and deformation. A study conducted by [PERSON] also used the two-dimensional DIC technique to characterize the deformation behavior of aligners materials [16]. This study highlighted the ability of \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Aligner** & **No. Point** & **3*** & **2*** & **1** & **2*** & **3*** \\ \hline \multirow{4}{*}{Spark Upper} & Axis & [mm] & [mm] & [mm] & [mm] & [mm] \\ \cline{2-7}  & X & 0.007 & 0.008 & - & 0.033 & 0.034 \\ \cline{2-7}  & Y & 0.007 & 0.003 & - & 0.01 & 0.02 \\ \cline{2-7}  & Z & 0.005 & 0.05 & - & 0.024 & 0.027 \\ \hline \multirow{4}{*}{Spark Lower} & \multicolumn{4}{c}{3} & 3 & 2 & 1 & 1 & 2 & 3 \\ \cline{2-7}  & X & 0.01 & 0.002 & 0.0015 & 0.014 & 0.014 & 0.002 \\ \cline{2-7}  & Y & 0.001 & 0 & 0.006 & 0.008 & 0.006 & 0.007 \\ \cline{2-7}  & Z & 0.011 & 0.009 & 0.0015 & 0.021 & 0.027 & 0.03 \\ \hline \hline \end{tabular}  
* indicates the maxillary points.  
\end{table} 
Table 4: Elastic deformation determined as the difference between the position of the gingival and the incisal tracker on the same tooth for Spark Trugen Material. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Aligner** & **No. Point** & **3*** & **2*** & **1** & **2*** & **3*** \\ \hline \multirow{4}{*}{Taglus Upper} & Axis & [mm] & [mm] & [mm] & [mm] & [mm] \\ \cline{2-7}  & X & 0.002 & 0.008 & & 0.019 & 0.044 \\ \cline{2-7}  & Y & 0.005 & 0.016 & & 0.01 & 0.009 \\ \cline{2-7}  & Z & 0.024 & 0.053 & & 0.026 & 0.026 \\ \hline \multirow{4}{*}{Taglus Lower} & \multicolumn{4}{c}{3} & 2 & 1 & 1 & 2 & 3 \\ \cline{2-7}  & X & 0.002 & 0.008 & 0.002 & 0.004 & 0.009 & 0.002 \\ \cline{2-7}  & Y & 0.001 & 0.01 & 0.005 & 0.006 & 0.003 & 0.007 \\ \cline{2-7}  & Z & 0.01 & 0.048 & 0.017 & 0.02 & 0.018 & 0.03 \\ \hline \hline \end{tabular}  
* indicates the maxillary points.  
\end{table} 
Table 5: Elastic deformation determined as the difference between the position of the gingival and the incisal tracker on the same tooth for Taglus Premium material. DIC to clearly delineate the phases of compressive behavior. The findings of this study are in full agreement with our results on the significant elastic deformation observed in the Spark and Taglus systems. Images obtained with a high-speed camera have the advantage of a precise measurement of the elastic volume changes [11]. The thickness of the aligner material impacts the force that it generates. The different thickness of the studied aligners was taken into account. ASTM D882-18 and the ISO standard 527 recommend rectangular shapes for tensile testing in thermoplastic materials with a thickness of less than 1 mm [11; 17], which also applies to Duran, with a thickness of 0.75 mm.