## 2 Materials and Methods
### Electromyographic Examination  
Surface electromyography (sEMG) is a significant diagnostic test to analyze muscular activity as well as the pathophysiological alterations in muscles, joints, and related structures. SEMG could, therefore, take part in the diagnostic process of muscle pain referred \begin{table}
\begin{tabular}{c c} \hline \hline
**Inclusion Criteria** & **Exclusion Criteria** \\ \hline Patients with a JIA diagnosis of at least six & \\ months earlier by the Pediatric Department of & Lacking medical history \\ the SS. Annunziata Hospital in Chieti, Italy & Diagnosis of inborn craniofacial syndrome \\ Age range 10–26 years & Presence of maxillofacial bone fracture or \\ No ongoing or previous orthodontic treatments & surgery in medical history \\ Compliance and ability to reliably report the & Previous TM] treatment medical history \\ manifestation of pain and perform & Diagnosis of other systemic diseases \\ instrumental examinations & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Inclusion/exclusion criteria. to as damage to the TMJ. The Teethan BTS TTMJOINT (SpA, Garbagnate Milanese, Italy, [[https://teethan.com/teethan-software/](https://teethan.com/teethan-software/)]([https://teethan.com/teethan-software/](https://teethan.com/teethan-software/))) software was used for the study, and a wireless surface electromyograph (EMG) was used to record the electrical activity of a muscle during its contractile activity with the use of six pairs of pre-gelled electrodes in order to process the data and graphically represent the biological phenomenon of contraction. Further information is available about the functioning of the electromyograph in the study by [PERSON] et al. [18]. Following the main orientation of the muscular fibers, the electrodes were positioned on the belly of the sternocleidomastoid (SCM), superficial masseter (MM), and anterior temporalis (TA) of the left and right sides. The tests were executed by the same clinician on all subjects, following the standardized protocols of Dr. [PERSON] [32; 33; 34]. The patients were seated upright on a chair without a headrest in a quiet room, with a natural and comfortable head posture, hands on their legs, and feet on the floor. Data recording started 5 min after electrode application to allow the conductive gel to adapt to skin moisture [35]. Three tests were performed as follows: the cotton test (COT6), the clenching test (CLE6), and the rotation test (ROT6). The first two--both lasting 5 s--allowed for the measurement of muscle activity in the maximum intercuspidation. COT6--also called the calibration test--was performed by positioning two cotton rolls occlusally between the back teeth, starting from the second premolars, so that the maximum strength of the muscles without dental contact is expressed and the Teethan software is calibrated for the individual patient. CLE6--or the acquisition test--was performed in normal intercuspidation, so that the changes in neuromuscular activity during dental contact are evaluated by the software and compared with those obtained with COT6. The third test, ROT6, which lasted for an indefinite time and detected sternocleidomastoid activity, consisted of having the patient rotate his head on one side and then on the other, making sure that no head tilting or teeth clenching and no slightly forced rotation occurred during and at the end of the movement, respectively. All tests were then processed by the software, thus extracting the following parameters:  
* POC: percentage overlapping coefficient (normal values: \(83\%\leq\mathrm{X}\leq 100\%\)), identifying which of the pairs of homologous muscles are prevalent. The ideal value was \(100\%\), indicating perfect symmetry between the muscles on the two sides. POC values of the anterior temporalis (POC TA), superficial masseter (POC MM), and sternocleidomastoid (POC SCM) were calculated. The POC TA and POC MM are related to the contacts between the anterior teeth and the posterior teeth, respectively.