Background and Objectives: Fibrillinopathies have different phenotypic expression: Marfan-like skeleton features, MLSF; mitral valve prolapse syndrome, MVPS; MASS phenotype, M = mitral valve prolapse, MVP, A = aortic root dilation, S = skeletal features, and the second S = (cutaneous) striae; Marfan Syndrome, MS. The study had the following main objectives: the correlation between disc displacement, DD (a major sign for temporomandibular joint dysfunction, TMDs) on magnetic resonance imaging, MRI, and aortic Z score (a major sign for aortic root dilation) on echocardiography; the predictive value of DD towards aortic Z score. DD had 2 types of severity: DD with reduction (the mild type, DDwR), and DD without reduction (the severe type, DDwoR). Materials and Methods: The type of fibrillinopathy was precised by clinical exam (systemic score), ophthalmic exam (for ectopia lentis), and echocardiography (aortic Z score, MVP). Medical treatment consisted of betablockers, BB (for patients with tachycardia), or angiotensin II receptor blockers, ARB. Surgical treatment was addressed to aortic root aneurysm, and severe mitral regurgitation, MR. DD benefited from dental conservatory treatment or surgical restoration. Results: DD-Z score had a powerful correlation in MASS (Rho = 0.787, p < 0.01), and in MS patients (Rho = 0.819, p < 0.01). For the entire sample, both DDwR-Z score and DDwoR-Z score had a moderate correlation (Rho = 0.469, and respectively 0.669). Furthermore, DD was an important predictor for Z score. DDwoR had a double power of prediction for the Z score compared with DDwR (B coefficient = 1.661 for DDwR and 3.281 for DDwoR). Conclusions: TMDs had a powerful correlation with aortic root dilation in MASS and MS patients from the sample. Likewise, TMDs was a major predictor for aortic root dilation, in the entire sample. In clinical practice, we can utilize an extracardiac finding, TMDs, obtained by a non-invasive technique, MRI, for cardiac severity stratification of fibrillinopathies.