## 3 Results  
The demographic details of participants (TMD patients and TMD-free participants) are summarized in Table 2.  
At baseline, reliability was high for the forces measured overall (single measurement intraclass correlation coefficient (ICC) 0.98, 95% CI 0.97-0.98); for TMD-free participants (0.96, 0.95-0.98) and TMD patients (0.96, 0.94-0.97); and for those with disc displacement (0.95, 0.89-0.98), myofascali pain (0.97, 0.95-0.99), and both (0.94, 0.89-0.97). There was evidence of an overall decrease in forces following multiple trials, with evidence that this differed by TMD status (interaction \(p\) = 0.026) and was observed only in the TMD-free group (1.3% lower forces per measurement taken, 95% CI 0.5-2.0%, \(p\) = 0.002) and not in the TMD group (effectively 0.0% change per measurement taken, 95% CI 0.8% lower-0.8% higher, \(p\) = 0.997). There was no evidence of differences in repeated measurement effects at baseline within the TMD patients' group by subtype (interaction \(p\) = 0.684). From an unadjusted model using baseline data, the force measure had good discriminating performance, with an area under the curve for a ROC curve (AUC) of 0.932 (95% CI 0.889-0.975) (ROC curve is shown in Figure 2). Using Youdon's J, a cut-point of 28.7 N was obtained, with lower values being associated with TMD. This would provide a sensitivity of 81% (exact 95% CI 69-90%) and a specificity of 91% (80-97%). To achieve a sensitivity of at least 90%, a cut-point of 35.4 N would be needed, also providing a specificity of 77%; a sensitivity of at least 95% would be achieved with a cut-point of 37.5 N, with a specificity of 75%. Adding the age, sex, height, and weight, each, incrementally did not improve this model (each likelihood ratio test \(p\) \(\geq\) 0.469, combined likelihood ratio test \(p\) = 0.899). A multinomial logistic regression model did not find evidence that forces could discriminate between subtypes (unadjusted Wald \(p\) = 0.127, adjusted for all the variables listed above Wald \(p\) = 0.235). Of the 118 baseline participants (62 TMD and 56 TMD-free), 104 (88%) were followed up at 6 months, with eight TMD and six TMD-free participants lost to follow-up (Chi-squared \(p\) = 0.713 for between-group differences in retention). There was no evidence of differences between those followed-up and those not followed-up in terms of sex ([PERSON]'s exact test \(p\) = 0.544) or age (Mann-Whitney U \(p\) = 0.077), with the median age of those lost to follow-up 22.0 versus 25.5 years). There was also no evidence of differences in baseline jaw-opening forces for those followed-up versus lost to follow-up for either group (Mann-Whitney U, TMD: \(p\) = 0.613, TMD-free: \(p\) = 0.160). For the TMD patients, subtype was not associated with loss to follow-up ([PERSON]'s exact test \(p\) = 0.310). Jaw-opening forces increased in the TMD patient group (n = 54) from a geometric mean (geometric SD, with these used due to the positive skew of the data) of 18.6 N (1.63) to 32.4 N (1.67), a 74.2% improvement (95% CI 60.5-89.0%, \(p\)-value for change <0.001) (Figure 3). In the TMD-free group (n = 50), forces were relatively unchanged at 49.0 N (1.54) and 48.3 N (1.53) at the two time points--a non-significant decrease of 1.5% (95% CI -9.6-7.2%, \(p\) = 0.720) (Figure 3). This closed the baseline difference from baseline when the TMD group's forces were 62.5% lower (54.7-68.2%) to 32.9% lower at follow-up (19.8%-43.8%), a statistically significant relative improvement (\(p\) < 0.001). \begin{table}