Comparative Cross-Sectional Assessment of Temporomandibular Dysfunction and Masticatory System Changes in Patients with Rheumatoid Arthritis and Temporomandibular Joint Osteoarthritis

Background/Objectives: Although the etiology and pathomechanism of temporomandibular joint osteoarthritis (TMJ OA) and rheumatoid arthritis (RA) are different, they can both lead to serious structural and functional changes in the masticatory system. This study aimed to assess and compare the prevalence and characteristics of functional changes in the masticatory system in RA and OA TMJ patients. Materials and Methods: This cross-sectional study included 40 RA patients meeting the 2010 ACR/EULAR criteria and 40 TMJ OA patients. Research diagnostic criteria for TMD (RDC/TMD) were used to assess functional changes. Results: Orofacial pain was a predominant TMD reported in 80% of RA patients and in 67.5% of OA TMJ patients. There was no difference in the orofacial pain intensity and degree of somatization between RA and OA TMJ patients (p = 0.114). Orofacial pain duration was statistically longer in OA TMJ patients than in RA patients (p = 0.003). The ranges of mandibular movement were limited but without any statistically significant differences between the groups compared for maximum active opening (p = 0.349) and maximum passive opening (p = 0.461). Patients with RA presented with more muscles affected with pain. The most painful muscles were the medial pterygoid muscles and the anterior belly of the digastric muscle for the right side (p = 0.006) and for the left side (p = 0.004), and the tendon of the temporal muscle (p = 0.011) and (p = 0.004). The pain intensity of these muscles was statistically higher in RA patients in comparison to OA TMJ patients. Predominant TMJ sounds were slight crepitations in both RA and OA TMJ patients, mainly during laterotrusion in OA (p = 0.000). Conclusions: Laterotrusion was the key movement differentiating TMD manifestations between the two groups. Early functional diagnosis of the temporomandibular joint and an interdisciplinary therapeutic approach, combining treatment of the underlying disease with therapy of the masticatory system disorders, are crucial to limit the progression of changes and improve masticatory function.