## 2 Materials and Methods  
In this study, 62 TMD patients and 56 TMD-free participants aged 15-84 were recruited from March 2018 to February 2019, with follow-up appointments completed in August 2019. This includes 4 additional TMD patients from our earlier analysis of baseline results [20]. Ethical approval was obtained from the Health and Disability Ethics Committees (HDEC) (approval number 17/NTB/171), and the study was conducted in full accordance with the World Medical Declaration of Helsinki. The clinical trial was registered in the Australia New Zealand Clinical Trials Registry ([[https://www.anzctr.org.au](https://www.anzctr.org.au)]([https://www.anzctr.org.au](https://www.anzctr.org.au)), accessed on 19 April 2018) and received the registration ID ACTRN12618000607279. Due to a lack of clinical data to base power calculations on at the start of the study, the target sample size was informed by blinded power calculations, looking at baseline differences between groups (TMD and TMD-free) prior to completing recruitment of participants. Details are included in our earlier publication [20], but, briefly, a 20% difference in geometric mean forces was determined likely to be of clinical importance, and, given an SD on the log-scale of 0.42, 80% power to detect this with a two-sided test at the 0.05 level required n = 57 participants in each group (114 in total). All participants were provided with a detailed explanation of the study. After obtaining written informed consent, oral-medicine specialists screened the participants according to the DC/TMD protocol (examining the range of mandibular movements, pain, joint sounds, occlusion, oral behavior, and musculoskeletal state) [5], and TMD patients were divided into three subcategories, based on TMD symptoms: \begin{tabular}{l l l l} (1) & Presence of myofasical pain (n = 17), \\ (2) & Disc displacement (n = 20), \\ (3) & Myofasical pain and disc displacement combined (n = 25). \\ \end{tabular}   
The inclusion and exclusion criteria for patients in both the TMD and TMD-free groups are given in Table 1.  
Baseline jaw-opening forces were recorded for both TMD patients and TMD-free participants [20]. In brief, the adjustable head device consisting of a 3D-printed headgear and chin caps connected to a 1000 N load cell was placed on the participants' head and tightened until there was a stable connection with the chin cap (Figure 1) [19; 20]. With their jaw held together, participants opened their mandible seven times as forcefully as possible for an average 2-s period before closing and pausing for a 3-s period between each attempt [19; 20]. Jaw-opening forces were recorded in a data-capture system (Biotronics Ltd., Dunedin, New Zealand) and analyzed by using the PicoLog Software (Biotronics Ltd.). Each of the seven jaw-opening attempts was recorded as a graph of mV variation during each movement, and the highest peak observed during each jaw-opening movement was recorded and measured. Mean force values were calculated for each participant after discarding the first (practice) and last attempt. The last attempt was discarded due to possible muscle fatigue. The output in mV was converted into force in Newtons by loading the 1000 N load cell with known force outputs, using a 5 KN load cell in an Instron universal testing machine (Instron 3369, Norwood, MA, USA), as described in our previous study [20]. During the initial visit to the clinic, TMD patients received a combination of treatments and were instructed to continue treatment for six months. Treatments included TMD self-management therapy (education and awareness, avoiding extreme jaw movements, avoid eating hard foods, applying cold and hot packs, and relaxation techniques, such as facial massage), non-steroidal anti-inflammatory drugs (NSAIDs), and the use of stabilization splints, depending on the severity of the TMD. The TMD-free group (comparison group) did not receive treatment.