## 4 Discussion  
The present study proposed and established a proof-of-concept for the synchronization of two electromechanical systems, 3D electromagnetic articulography, and surface electromyography, explaining it in detail so that it can be replicated by other research groups. No significant interferences between both systems were detected in the recordings. The implementation of the synchronization and further analysis aims to improve understanding of the complexity of mandibular functional movements, which may be applied to study different clinical situations. The study of functional movements through analysis of kinematics and muscle activity is widely approached in various disciplines [32], including dentistry [1; 2; 3; 5; 7; 8; 9; 11; 13; 14; 16; 33], which reveals the importance of analyzing these complex movements by various methods that complement each other. Simultaneous measurements of different biomechanical variables of mandibular movements have been carried out for many years. [PERSON] measured the speed of contraction, the EMG activity, and the tension applied controlled by putting different weights [34]. More recent studies have also analyzed mandibular movements with simultaneous recordings of electromyographic activity and jaw movements in dentate individuals [8] and patients with maxillary and mandibular complete dentures [13] without synchronizing both recordings. These studies, even with clinical value, have limitations due to the lack of synchronization of their recordings or lack of more detailed explanation of the methodology employed. This limits the extrapolation of their results in the clinical understanding of mandibular movements, which reveals the need for a more complete analysis. Other authors have developed studies demonstrating the concern to synchronize the signals recorded by different electromechanical equipment related to mandibular movements \begin{table}
\begin{tabular}{c c c c} \hline  & **Without EMA** & **With EMA** & **Difference** \\ \hline LT & 31.6 \(\upmu\)V & 31.3 \(\upmu\)V & 1\% \\ RT & 19.6 \(\upmu\)V & 20.1 \(\upmu\)V & 3\% \\ LM & 15.8 \(\upmu\)V & 15.3 \(\upmu\)V & 3\% \\ RM & 10.2 \(\upmu\)V & 9.2 \(\upmu\)V & 10\% \\ \hline \end{tabular}
\end{table} 
Table 2: EMGrms mean. Figure 6: EMGrms signal from the right masseter muscle (blue) and MM (red) synchronized. with the electromyographic activity of the muscles of the stomatognathic system [6; 7; 9; 10; 11; 14], but these studies did not provide enough information regarding the methods to be replicated. Some studies have shown the synchronization between electromedical equipment applied to different analyses of the stomatognathic system, using arrangements or equipment specially developed for this purpose. [PERSON] et al. designed and built a special device to combine recordings of vibration and EMG activity [35]. [PERSON] et al. performed a master-slave arrangement for palatal pressure, mandibular movement, and EMG recordings with 1 ms delay in the synchronization [36]. Some researchers used a specific synchronization module for EMG signal analysis and occlusal force distribution analyzed using the T-SCAN system [37; 38; 39; 40], and [PERSON] et al. synchronized EMG records of the masseter muscle and the mandibular movements using a commercial system with 2D magnetic sensors [16]. Other studies performed the synchronization of the recordings by generating an independent and identifiable event in the signals acquired by different systems. [PERSON] used a light signal to synchronize EMG and cinematography recordings [1]. A pulse generator was used to synchronize EMG activity and mandibular movements by videofluorography and cinardiography [3; 4; 5]. [PERSON] et al. synchronized the recordings of mandibular movements obtained by a Kinect sensor and EMG activity through a computational custom-made system [15]. More recently, [PERSON] et al. also used a synchronizing signal and post-processed the recordings to synchronize them [41].