## 2 Materials and Methods
### Evaluation for TMD  
Prior to beginning fixed orthodontic therapy, each patient was routinely evaluated for signs and symptoms of TMD. Clinical assessment was carried out by a senior calibration (A.U.) examiner and was based on the parameters given in the RDC/TMD criteria [16]. The two characteristics--assessment of myofascali pain and assessment of disc dysfunction--were assessed separately.  
Assessment of myofasical pain was done using the modified pericranial tenderness score (PTS), described in previous studies [17; 18; 19; 20; 21]. This included palpation of the masticatory muscles (masseter and temporalis muscles) and cervical muscles (sternocleidomastoid, trapezius, and subocipital muscles). We used a pressure-controlled palpation technique described by [PERSON] et al. [22]. Palpation was done using the index and middle fingers; small circular movements were carried out for the masticatory and subocipital muscles, while the other cervical muscles were gently pinched. Each muscle was palpated for at least three seconds. The tenderness on palpation at each muscle was graded from 0 to 3, with 0 indicating normal tone and 1, 2, and 3 indicating mild, moderate, and severe tenderness, respectively. The final PTS score was divided into two components: the masticatory muscle tenderness score (MTS) for the first group of muscles and the cervical muscle tenderness score (CTS) for the second group. Both the MTS and CTS were calculated as the mean for the scores of each muscle in that group [18; 21].  
A calibration session was performed every 2 years with a second senior examiner to assess the degree of the inter-rating agreement between clinicians. The results were found to have acceptable reliability (the K value for combined intraclass correlation for within-subject variability and between-subject variability was 0.92, 95% CI, 0.89-0.96, \(p<0.001\)) that was consistent with previous reports [21].  
To assess for disc displacement, two components were considered. The presence of clicking was assessed through direct examination (by placing the operator's fingers over the joint region), as well as by auscultation. The presence or absence of clicking was recorded during opening and closing movements. The range of motion of the joint was assessed by checking the degree of mouth opening and opening patterns.  
The evaluation methods for TMD were repeated at the baseline and at the end of treatment, and they were continued until one year after the fixed appliance was removed. According to orthodontic clinical protocol, the development of TMD symptoms was routinely evaluated at the baseline before treatment (T0), immediately after treatment (T1), and one year after treatment (T2). A psychological assessment, according to Axis 1 of the _Diagnostic and Statistical Manual of Mental Disorders_, _4 th Edition_, was then carried out at the baseline before the start of orthodontic treatment. The presence of anxiety disorders and depression was investigated with an SCID-I-structured, semi-structured clinical interview [22], along with headache, neck, and shoulder pain parameters and somatic symptoms (colitis, gastritis, swallowing or digestion difficulty, phobias, tinnitus, dizziness, cramps, paresthesia, back pain, headache, and oral parafunction) [18; 19; 20; 21; 22; 23]. The SCID-I assessment was carried out by a clinician with 15 years of experience in treating TMD patients, calibrated for SCID analysis by a senior psychologist of the local headache and orofacial pain center.  
The primary outcome parameter studied was the development of TMD during and one year after orthodontic treatment. The influence of multiple risk factors (including demographic and clinical data) on the development of TMD was also assessed using multivariate logistic regression analysis. The ORs were adjusted for age, sex, and presence of anxiety or mood disorders. The significance of the analysis was evaluated by setting the \(p\) value to less than 0.05.